Method and apparatus for server broadcast of time-converging multi-media streams

[0002] The present invention pertains to the field of playback of streaming media (such as audio and audio-visual works) which are retrieved from sources having non-deterministic delays such as, for example, servers (such as file servers or streaming media servers) broadcasting data via the Internet. In particular, the present invention pertains to method and apparatus for providing playback of audio or audio-visual works received from sources having non-deterministic delays. In further particular, the present invention pertains to method and apparatus for providing continuous playback of streaming media from sources having non-deterministic delays such as, for example, servers (such as file servers or streaming media servers) broadcasting data via the Internet, an Intranet, or the like.

[0003] Many digitally encoded audio and audio-visual works are stored as data on servers (such as file servers or streaming media servers) that are accessible via the Internet for users to download. FIG. 1 shows, in schematic form, how such audio or audio-visual works are distributed over the Internet. As shown in FIG. 1, media broadcast server 2000 accesses data representing the audio or audio-visual work from storage medium 2100 and broadcasts the data to multiple recipients 2300₁to 2300_nacross non-deterministic delay network 2200. In this system there are two main sources of random delay: (a) delay due to media broadcast server 2000 accessing storage medium 2100 and (b) delay due to the congestion, interference, and other delay mechanisms within network 2200.

[0004] One well known technique for providing playback of the audio or audio-visual work is referred to as batch playback. Batch playback entails downloading an entire work and initiating playback after the entire work has been received. Another well known technique for providing playback of the audio or audio-visual work is referred to as “streaming.” Streaming entails downloading data which represents the audio or audio-visual work and initiating playback before the entire work has been received.

[0005] There are several disadvantages inherent in both of these techniques. A prime disadvantage of batch playback is that the viewer/listener must wait for the entire work to be downloaded before any portion of the work may be played. This can be tedious since the viewer/listener may wait a long time for the transmission to occur, only to discover that the work is of little or no interest soon after playback is initiated. The streaming technique alleviates this disadvantage of batch playback by initiating playback before the entire work has been received. However, a disadvantage of streaming is that playback is often interrupted when the flow of data is interrupted due to network traffic, congestion, transmission errors, and the like. These interruptions are tedious and annoying since they occur randomly and have a random duration. In addition, intermittent interruptions often cause the context of the playback stream to be lost as the viewer/listener waits for playback to be resumed when new data is received. A further disadvantage of streaming is that a user or client is required to poll for additional data according to its rate of use of the data. In this manner, a user or client using data at a rapid rate has to make additional requests for data at a higher rate than a user or client using the data at a slower rate.

[0006] A further disadvantage in broadcasting audio or audio-visual works using prior art methods occurs when clients request data asynchronously from the media server. Currently, there are two prior art methods for broadcasting a work to multiple clients requesting data at arbitrary times. The first prior art method involves re-broadcasting the work at regular intervals. This prior art method is efficient for the media server since its storage access patterns and load are basically independent of the number of clients receiving the audio or audio-visual work. A major problem with this prior art method is that clients must join a re-broadcast in the middle of the audio or audio-visual work currently being broadcast, or wait for the next re-broadcast to begin to view the start of the audio or audio-visual work.

[0007] The second prior art method initiates a re-broadcast of the audio or audio-visual work each time a client requests to view the audio or audio-visual work. This prior art method has the advantage that client do not have to wait to view the start of work and begin reception immediately. A major problem with this second prior art method is that the media server must monitor, track and fulfill the request of each client requesting data individually. This causes a dramatic increase in server load during heavy use since multiple requests arrive simultaneously, and storage access patterns and broadcast load vary widely. As a result, the media server's capacity to serve a number of clients in a reasonable time is limited.

[0008] As one can readily appreciate from the above, a need exists in the art for a method and apparatus for providing substantially continuous playback of streaming media such as audio and audio-visual works received from sources having non-deterministic delays such as a file server broadcasting data via the Internet. In addition, a need exists in the art for a method and apparatus for broadcasting streaming media on an efficient basis that maximizes broadcast media server capacity.

[0009] Embodiments of the present invention advantageously satisfy the above-identified need in the art and provide method and apparatus for broadcasting streaming media on an efficient basis that maximizes broadcast media server capacity.

[0010] One embodiment of the present invention is a method for broadcasting information from a server to a client which comprises the steps of: (a) broadcasting information at predetermined starting times; (b) broadcasting time-scale modified versions of the information for periods of time, at least one period starting before or after one of the predetermined starting times; (c) receiving a request for the information from the client between the predetermined starting times; and (d) transmitting one of the time-scale modified versions to the client.

[0011] FIG. 1 shows, in schematic form, how audio or audio-visual works are broadcast from a server (for example, a file server or a streaming media server) to recipients over a network such as, for example, the Internet;

[0012] FIG. 2 shows a block diagram of an embodiment of the present invention which provides substantially continuous playback of an audio or audio-visual work received from a source having non-deterministic delays such as a server (for example, a file server or a streaming media server) broadcasting data via the Internet;

[0013] FIG. 3 shows, in pictorial form, low and high thresholds used in one embodiment of Capture Buffer 400 for the embodiment of the present invention shown in FIG. 2;

[0014] FIG. 4 shows a graph of playback rate versus amount of data in Capture Buffer 400 using eqns. (2)-(4) for the embodiment of the present invention shown in FIG. 2;

[0015] FIG. 5 shows, in graphical form, relative amounts of data at an input and an output of TSM System 800 in the embodiment of the present invention shown in FIG. 2 during time-scale expansion, i.e., slow down of the playback rate of the streaming media;

[0016] FIG. 6 shows, in graphical form, relative amounts of data at an input and an output of TSM System 800 compression in the embodiment of the present invention shown in FIG. 2 during time-scale compression, i.e., speed up of the playback-rate of the streaming media;

[0017] FIG. 7 shows a block diagram of media server 3000 which re-broadcasts an audio or audio-visual work is at regular intervals;

[0018] FIG. 8A shows, in graphical form, encoding, transmitting and decoding portions of an audio or audio-visual work;

[0019] FIG. 8B shows, in graphical form, a composition and transmission method utilized by Work Stream 3200 to form and transmit a TDM composite signal to Multicaster 3300 of embodiment 3000 shown in FIG. 7 of embodiment 3000;

[0020] FIG. 9A shows a graph of location of a segment (offset from an origin) of the audio or audio-visual work being re-broadcast by embodiment 3000 shown in FIG. 7 as a function of time;

[0021] FIG. 9B shows a graph of work-encoded-data-block number (offset from an origin) of the audio or audio-visual work being re-broadcast by embodiment 4000 shown in FIG. 10 as function of time;

[0022] FIG. 9C shows a graph of position (offset from an origin) of an audio or audio-visual work being received by a media playback device that incorporates storage of the audio or audio-visual work, such as, for example a digital VCR, hard-disk based VCR, and the like;

[0023] FIG. 10 shows a block diagram of embodiment 4000 of the present invention that transitions asynchronously arriving requests to receive a particular audio or audio-visual work to synchronous re-broadcasts of the audio or audio-visual work;

[0024] FIG. 11A shows a graph of location (offset from an origin) of an audio or audio-visual work being re-broadcast by embodiment 5000 shown in FIG. 12 as a function of time in accordance with the further aspect of the present invention;

[0025] FIG. 11B shows, in graphical form, encoding portions of a Time-Scale Modified audio or audio-visual work to form Time-Scale Modified Leaders;

[0026] FIG. 12 shows a block diagram of embodiment 5000 of the present invention which: (a) transmits Time-Scale Modified Leaders; (b) joins re-broadcast offset streams of an audio or audio-visual work; and (c) transmits offset streams of an audio or audio-visual work;

[0027] FIG. 13 shows a graph of location (offset from an origin) in normal and Time-Scale Modified versions of offset re-broadcasts of an audio or audio-visual work versus time on the horizontal axis;

[0028] FIG. 14 shows a block diagram of embodiment 21000 of the present invention which transmits information relating to the playback speed and/or content of media data to clients receiving the media data; and

[0029] FIG. 15 shows a block diagram of embodiment 24000 of the present invention in which information relating to the playback speed and/or content of the media data being broadcast to clients is embedded in the media work.

[0030] FIG. 2 shows a block diagram of embodiment 1000 of the present invention which provides substantially continuous playback of an audio or audio-visual work received from a source having non-deterministic delays such as a server (for example, a file server or a streaming media server) broadcasting via the Internet. As shown in FIG.2, streaming data source 100 provides data representing an audio or audio-visual work through network 200 to User System 300 (US 300), which data is received at a non-deterministic rate by US 300. Capture Buffer 400 in US 300 receives the data as input. In a preferred embodiment of the present invention, Capture Buffer 400 is a FIFO (First In First Out) buffer existing, for example, in a general purpose memory store of US 300.

[0031] In the absence of delays in arrival of data at US 300 from network 200, the amount of data in Capture Buffer 400 ought to remain substantially constant as a data transfer rate is typically chosen to be substantially equal to a playback rate. However, as is well known to those of ordinary skill in the art, pauses and delays in transmission of the data through network 200 to Capture Buffer 400 cause data depletion therein. Data depletion in Capture Buffer 400 occurs because, simultaneously, data is input thereto from network 200 while data is output (for example, at a constant rate) therefrom to satisfy data use requirements of Playback System 500. As should be clear to those of ordinary skill in the art, if data transmitted to US 300 is delayed long enough, data in Capture Buffer 400 will be consumed, and Playback System 500 must pause until a sufficient amount of data has arrived to enable resumption of playback. Thus, a typical playback system must constantly check for arrival of new data while the playback system is paused, and it must initiate playback once a sufficient amount of new data is received.

[0032] In accordance with the present invention, data input to Capture Buffer 400 of US 300 is buffered for a predetermined amount of time, which predetermined amount of time typically varies, for example, from one (1) second to several seconds. Then, Time-Scale Modification (TSM) methods are used to slow the playback rate of the audio or audio-visual work to substantially match a data drain rate required by Playback System 500 with a streaming data rate of the arriving data representing the audio or audio-visual work. As is well known to those of ordinary skill in the art, presently known methods for Time-Scale Modification (“TSM”) enable digitally recorded audio to be modified so that a perceived articulation rate of spoken passages, i.e., a speaking rate, can be modified dynamically during playback. During Time-Scale expansion, TSM System 800 requires less input data to generate a fixed interval of output data. Thus, in accordance with the present invention, if a delay occurs during transmission of the audio or audio-visual work from network 200 to US 300 (of course, it should be clear that such delays may result from any number of causes such as delays in accessing data from a storage device, delays in transmission of the data from a media server, delays in transmission through network 200, and so forth), the playback rate is automatically slowed to reduce the amount of data drained from Capture Buffer 400 per unit time. As a result, and in accordance with the present invention, more time is provided for data to arrive at US 300 before the data in Capture Buffer 400 is exhausted. Advantageously, this delays the onset of data depletion in Capture Buffer 400 which would cause Playback System 500 to pause.

[0033] As shown in FIG. 2, Capture Buffer 400 receives the following as input: (a) media data input from network 200; (b) requests for information about the amount of data stored therein from Capture Buffer Monitor 600; and (c) media stream data requests from TSM System 800. In response, Capture Buffer 400 produces the following as output: (a) a stream of data representing portions of an audio or audio-visual work (output to TSM System 800); (b) a stream of location information used to identify the position in the stream of data (output to TSM System 800); and (c) the amount of data stored therein (output to Capture Buffer Monitor 600). It should be well known to those of ordinary skill in the art that Capture Buffer 400 may include a digital storage device. There are many methods well known to those of ordinary skill in the art for utilizing digital storage devices, for example a “hard disk drive,” to store and retrieve general purpose data. There exist many commercially available apparatus which are well known to those of ordinary skill in the art for use as a digital storage device such as, for example, a CD-ROM, a digital tape, a magnetic disc.

[0034] As further shown in FIG. 2, and in accordance with the present invention, TSM Rate Determiner 700 receives the following as input: (a) a signal (from Capture Buffer Monitor 600) that represents the amount of data present in Capture Buffer 400; (b) a signal (output, for example, from Playback System 500 or from another module of US 300) that represents a current data consumption rate of Playback System 500; (c) a low threshold value parameter (T_Lwhich is described in detail below) for the amount of data in Capture Buffer 400; (d) a high threshold value parameter (T_Hwhich is described in detail below) for the amount of data in Capture Buffer 400; (e) a parameter designated Interval_Size; and (f) a parameter designated Speed_Change_Resolution. In response, TSM Rate Determiner 700 produces as output a rate signal representing a TSM rate, or playback rate, which can help better balance the data consumption rate of Playback System 500 with an arrival rate of data at Capture Buffer 400.

[0035] In a preferred embodiment of the present invention, TSM Rate Determiner 700 uses the parameter Interval_Size to segment the input digital data stream in Capture Buffer 400 and to determine a single TSM rate for each segment of the input digital stream. Note, the length of each segment is given by the value of the Interval_Size parameter.

[0036] TSM Rate Determiner 700 uses the parameter Speed_Change_Resolution to determine appropriate TSM rates to pass to TSM System 800. A desired TSM rate is converted to one of the quantized levels in a manner which is well known to those of ordinary skill in the art. This means that the TSM rate, or playback rate, can change only if the desired TSM rate changes by an amount that exceeds the difference between quantized levels, i.e., Speed_Change_Resolution. As a practical matter then, parameter Speed_Change_Resolution filters small changes in TSM rate, or playback rate. The parameters Interval_Size and Speed_Change_Resolution can be set as predetermined parameters for embodiment 1000 in accordance with methods which are well known to those of ordinary skill in the art or they can be entered and/or varied by receiving user input through a user interface in accordance with methods which are well known to those of ordinary skill in the art. However, the manner in which these parameters are set and/or varied are not shown for ease of understanding the present invention.

[0037] As still further shown in FIG. 2, TSM System 800 receives as input: (a) a stream of data representing portions of the audio or audio-visual work (output from Capture Buffer 400); (b) a stream of location information (output from Capture Buffer 400) used to identify the position in the stream of data being sent, for example, a sample count or time value; and (c) the rate signal specifying the desired TSM rate, or playback rate (output from TSM Rate Determiner 700).

[0038] In accordance with the present invention, TSM System 800 modifies the input stream of data in accordance with well known TSM methods to produce, as output, a stream of samples that represents a Time-Scale Modified signal. The Time-Scale modified output signal contains fewer samples per block of input data if Time-Scale Compression is applied, as shown in FIG. 6. Similarly, if Time-Scale Expansion is applied, the output from TSM System 800 contains more samples per block of input data, as shown in FIG. 5. Thus, TSM System 800 can create more samples than it is given by creating an output stream with a slower playback rate (Time-Scale Expanded). Similarly, TSM System 800 can create fewer samples than it is given by creating an output stream with a faster playback rate (Time-Scale Compressed). In a preferred embodiment of the present invention, the TSM method used is a method disclosed in U.S. Pat. No. 5,175,769 (the '769 patent), which '769 patent is incorporated by reference herein, the inventor of the present invention also being a joint inventor of the '769 patent. Thus, the output from TSM System 800 is a stream of samples representing portions of the audio or audio-visual work, which output is applied as input to Playback System 500. Playback System 500 plays back the data output from TSM System 800. There are many well known methods of implementing Playback System 500 that are well known to those of ordinary skill in the art. For example, many methods are known to those of ordinary skill in the art for implementing Playback system 500, for example, as a playback engine.

[0039] In accordance with the present invention, the stream of digital samples output from TSM System 800 has a playback rate, supplied from TSM Rate Determiner 700, that provides a balance of the data consumption rate of TSM System 800 with the arrival rate of data input to US 300. Note that, in accordance with this embodiment of the present invention, the data consumption rate of Playback System 500 is fixed to be identical to the data output rate of TSM System 800. Thus, when a playback rate representing Time-Scale Expansion is output from TSM Rate Determiner 700 and applied as input to TSM System 800, the number of data samples required per unit time by TSM System 800 is reduced in proportion to the amount of Time-Scale Expansion. A reduction in the number of data signals sent to TSM System 800 slows the data drain-rate from Capture Buffer 400 and, as a result, less data from Capture Buffer 400 is consumed per unit time. This, in turn, increases the amount of playback time before a pause is required due to emptying of Capture Buffer 400.

[0040] As one of ordinary skill in the art should readily appreciate, although the present invention has been described in terms of slowing down playback, the present invention is not thusly limited and includes embodiments where the playback rate is increased in situations where data arrives in Capture Buffer 400 at a rate which is faster than the rate at which it would be consumed during playback at a normal rate. In this situation, the playback rate is increased and the data is consumed by TSM System 800 at a faster rate to avoid having Capture Buffer 400 overflow.

[0041] As one of ordinary skill in the art can readily appreciate, whenever embodiment 1000 provides playback rate adjustments for an audio-visual work, TSM System 800 speeds up or slows down visual information to match the audio in the audio-visual work. To do this in a preferred embodiment, the video signal is “Frame-subsampled” or “Frame-replicated” in accordance with any one of the many methods known to those of ordinary skill in the prior art to maintain synchronism between the audio and visual portions of the audio-visual work. Thus, if one speeds up the audio and samples are requested at a faster rate, the frame stream is subsampled, i.e. frames are skipped.

[0042] Although FIG. 2 shows embodiment 1000 to be comprised of separate modules, in a preferred embodiment, Playback System 500, Capture Buffer Monitor 600, TSM Rate Determiner 700, and TSM System 800 are embodied as software programs or modules which run on a general purpose computer such as, for example, a personal computer. It should be well known to one of ordinary skill in the art, in light of the detailed description above, how to implement these programs or modules in software.

[0043] As should be clear to those of ordinary skill in the art, embodiments of the present invention include the use of any one of a number of algorithms for determining the playback rate to help balance the rate of data consumption for playing back the audio or audio-visual works with the rate of data input from network 200 having non-deterministic delays. In one embodiment of the present invention, the playback rate is determined to vary with the fraction of Capture Buffer 400 that is filled with data. For example, for each 10% decrement of data depletion, the playback rate is reduced by 10%, except when the input data contains an “end” signal. It should be clear to those of ordinary skill in the art how to modify this algorithm to achieve any of a number of desired balance conditions. For example, in situations where a delay duration can vary drastically, a non-linear relationship may be used to determine the playback rate. One non-linear function that may be used is the inverse tangent function. In this case,

[0044] Playback Rate=tanh⁻¹((2* #samples_in_buffer/elements_in_buffer))−1)  (1)

[0045] where #samples_in_buffer is the number of samples of data in Capture Buffer 400 and elements_in_buffer is the total number of samples of data that can be stored in Capture Buffer 400.

[0046] In a preferred embodiment of the present invention, a low threshold (T_L) value and a high threshold (T_H) value are be used to construct a piece-wise graph of playback rate versus amount of data in Capture Buffer 400. FIG. 3 shows, in pictorial form, how T_Land T_Hrelate to the amount of data in Capture Buffer 400. These thresholds are used in accordance with the following set of equations:

[0047] For 0<=X<=T_LPlayback Rate=Scale * tanh⁻¹((X−T_L)/T_L)  (2)

[0048] For T_L<X<T_HPlayback Rate=1.0 (the default playback rate)  (3)

[0049] For T_H<=X<=Max Playback Rate=Scale * tanh⁻¹((X−T_H)/(Max−T_H))  (4)

[0050] where Scale is arbitrary scale factor.

[0051] FIG. 4. shows a graph of playback rate versus amount of data in Capture Buffer 400 using eqns. (2)-(4). From FIG. 4, one can readily appreciate that for small deviations from an ideal amount of data in Capture Buffer 400 (origin 0 in FIG. 4), changes in the playback rate are linear; however, larger deviations generate a more pronounced non-linear response. Further, changes in the amount of data in Capture Buffer 400 which remain between low threshold level T_Land high threshold level T_Hdo not cause any change in playback rate. The parameters T_Land T_Hcan be set as predetermined parameters for embodiment 1000 in accordance with methods which are well known to those of ordinary skill in the art or they can be entered and/or varied by receiving user input through a user interface in accordance with methods which are well known to those of ordinary skill in the art. However, the manner in which these parameters are set and/or varied are not shown for ease of understanding the present invention.

[0052] As should be clear to those of ordinary skill in the art, the inventive technique for providing substantially continuous playback may be combined with any number of apparatus which provide time-scale modification and may be combined with or share components with such systems.

[0053] It should be clear to those of ordinary skill in the art, in light of the detailed description set forth above, that in essence, embodiments of the present invention (a) determine a measure of a mismatch between a data arrival rate and a data consumption rate and (b) utilize time-scale modification to adjust these rates. Various embodiments of the invention utilize various methods (a) for determining information which indicates the measure of the mismatch and (b) for determining a playback rate which enables time-scale modification to adjust for the mismatch in a predetermined amount.

[0054] In light of this, in another embodiment of the present invention, the playback system determines that there is a data mismatch because it determines a diminution in the arrival of data for playback or subsequent distribution. In response, the playback system sends this information to the TSM Rate Determiner to develop an acceptable playback rate. For example, the playback rate may be reduced by a predetermined amount based on an input parameter or in accordance with any one of a number of algorithms that may be developed by those of ordinary skill in the art.

[0055] Embodiments of the present invention are advantageous in enabling a single-broadcast system utilizing a broadcast server to provide a single broadcast across one or more non-deterministic delay networks to multiple recipients, for example across the Internet and/or other networks such as Local Area Networks (LANs) and Wide Area Networks (WANs). In such a single-broadcast system, the path to each recipient varies. In fact, the path to each recipient may dynamically change based on loading, congestion and other factors. Therefore, the amount of delay associated with the transmission of each data packet that has been sent by the broadcast server varies. In prior art client-server schemes, each recipient has to notify the broadcast server of its readiness to receive more data, thereby forcing the broadcast server to serve multiple requests to provide a steady stream of data at the recipients' data ports. Advantageously, embodiments of the present invention enable the broadcast server to send out a steady stream of information, and the recipients of the intermittently arriving data to adjust the playback rate of the data to accommodate the non-uniform arrival rates. In addition, in accordance with the present invention, each of the recipients can accommodate the arrival rates independently.

[0056] Another aspect of the present invention advantageously involves simplification of a transmission protocol used for communication of streaming media between a client and, for example, a server such as a media or broadcast server. In accordance with this additional aspect of the present invention, an inventive transmission protocol comprises the client's sending a data transmission rate to the media or broadcast server. In response, the server transmits data to the server substantially at that rate. In one embodiment of the present invention, the data transmission rate is in the form of a playback rate for a work. In this case, the server adjusts its data transmission rate in a manner which is well known to those of ordinary skill in the art so that the amount of data received by the client substantially matches the client's playback rate for the work. Thus, for embodiments of this aspect of the present invention, the broadcast server need not change its distribution rate unless and until a new request is received from the client. As one can readily appreciate, the inventive transmission protocol is advantageous because its use reduces: (a) a network protocol bandwidth required for streaming by substantially reducing repeated requests for data from the client and (b) the number of messages the server must process.

[0057] Another aspect of the present invention pertains to media broadcasting wherein media or broadcast servers begin broadcasts of a particular work (for example, the day's news) at regular time intervals, for example, every 5 minutes. In accordance with an embodiment of the present invention, a client that sends a request to view or listen to the particular work is sent a stream of the particular work (substantially immediately) which is closest (in the temporal sense) to the beginning of a broadcast of the particular work (in a manner that will be described in detail below) rather than waiting for a re-broadcast to begin or joining an in-progress broadcast. After a transition period (to be described in detail below), the client joins one of the regular broadcasts and receives data therefrom. Advantageously, in accordance with the present invention, there is a reduction in client a wait time and a reduction in client load for the media or broadcast servers. Although embodiments of the present invention are described below in the context of broadcasting data for ease of understanding the invention, it should be understood that the present invention is not thereby limited. In fact, among other things, embodiments of the present invention can also be applied to accessing data as well.

[0058] FIG. 7 shows a block diagram of embodiment 3000 of a media server which re-broadcasts an audio or audio-visual work at regular intervals. As shown in FIG. 7, Storage Device 3100 is a storage device of a type which is well known to those of ordinary skill in the art. Storage Device 3100 stores a representation (preferably a digital representation, or any representation that can be converted to a digital representation in accordance with methods which are well known to those of ordinary skill in the art) of an audio or audio-visual work or data of interest to a user (such as a stream of stock quotes, market data, advertisements, and so forth). Storage Device 3100 receives, as input, data requests from Work Streamer 3200, and provides, as output, the data requested.

[0059] As further shown in FIG. 7, Work Streamer 3200 receives as input: (a) a code (for example, a number) which represents a desired Re-broadcast Interval (“RBI”) (from Re-broadcast Interval Determiner 3700); (b) a code (for example, a number) which represents a desired number of Time-Division Multiplexed (TDM) channels (from Re-broadcast Interval Determiner 3700); (c) a code (for example, a number) which represents the duration of the audio or audio-visual work being re-broadcast (from Re-broadcast Interval Determiner 3700); and (d) data from Storage Device 3100. Work Streamer 3200 produces, as output, a Time-Division Multiplexed composite signal (described in detail below), which output is applied as input to Multicaster 3300. As will be described in detail below, in accordance with the preferred embodiment of the present invention, Work Streamer 3200 creates numerous re-broadcasts of the audio or audio-visual work by sending appropriately interleaved segments of the work in the form of the Time-Division Multiplexed signal to Multicaster 3300. Advantageously, in accordance with the preferred embodiment of the present invention, data accesses to Storage Device 3100 are organized by Work Streamer 3200 to reduce seek time, decrease latency, and increase throughput by interleaving and caching accesses to data representing the audio or audio-visual work. It should be clear to those of ordinary skill in the art that embodiments of this aspect of the present invention are not limited to generating the composite Time-Division Multiplexed signal and include embodiments where the data for the various re-broadcasts are each generated from a separate signal.

[0060] As still further shown in FIG. 7, Re-broadcast Interval Determiner (“RBID”) 3700 receives, as input, (a) a code (for example, a number) which represents the duration of an audio or audio/visual work and (b) a code (for example, a number) that represents the number of re-broadcast offset channels (to be described in detail below). RBID 3700 produces, as output: (a) a code (for example, a number) which represents a desired Re-broadcast Interval (“RBI”) (sent to Work Streamer 3200); (b) a code (for example, a number) which represents a desired number of Time-Division Multiplexed (TDM) channels (sent to Work Streamer 3200); (c) a code (for example, a number) which represents the duration of the audio or audio-visual work being re-broadcast (sent to Work Streamer 3200). In accordance with the present invention, RBID 3700 computes the RBI by applying one of a number of formulas. In the preferred embodiment of the present invention, the following formula is used:

[0061] RBI=Duration of audio or audio-visual work/No. of re-broadcast offset channels  (5)

[0062] As yet still further shown in FIG. 7, Multicaster 3300 receives, as input: (a) a data stream (the Time-Division Multiplexed composite signal) from Work Streamer 3200 and (b) client information (for example, control and destination) from Request Processor 3500. Multicaster 3300 produces, as output, data (for example, message packets) directed toward particular clients for re-broadcast on a network such as the Internet, WAN, LAN, etc. In accordance with the present invention, Multicaster 3300 manages a list of all clients that should receive data from particular portions of the TDM composite signal in accordance with any one of a number of methods which are well known to those of ordinary skill in the art. Then, whenever the particular portion of data in the TDM composite signal is received from Work Streamer 3200, Multicaster 3300 sends the particular portion of data to all clients (recipients) in the list who are to receive the particular portion of data (also known as multicasting). Many methods for broadcasting a portion of data from a data stream (for example, a Time-Division Multiplexed composite signal) to multiple recipients are well known to those of ordinary skill in the art. Control information from Request Processor 4500 is used in accordance with methods that are well known to those of ordinary skill in the art to modify the list of recipients, for example, to add a recipient, or to remove a recipient from the list of destinations when the recipient no longer desires to receive data from the server.

[0063] As yet again still further shown in FIG. 7, Request Processor 3500 receives, as input, requests for data from clients connected via Network 3990 (for example, an Internet, WAN, LAN, or the like). In response, Request Processor 3500 produces, as output, information identifying the client and appropriate re-broadcast control information such as, for example, “request data that is identified by an appropriate data identifier,” “disconnect,” and other messages that are used to obtain data from embodiment 3000. It should be clear to those of ordinary skill in the art, that such information identifying the client and appropriate re-broadcast control information may be obtained: (a) by dialogs between the client and Request Processor 3500 in accordance any one of many methods that are well known to those of ordinary skill in the art including, without limitation, by use of forms that are contained on web pages that are transmitted to the client over Network 3990 in accordance any one of the many methods that are well known to those of ordinary skill in the art.

[0064] Although FIG. 7 shows embodiment 3000 to be comprised of separate modules, in a preferred embodiment, the modules are embodied as software programs or modules which run on a general purpose computer such as, for example, a personal computer. It should be well known to one of ordinary skill in the art, in light of the detailed description above, how to implement these programs or modules in software.

[0065] Conversely, components of embodiment 4000 may exist in separate locations connected to one another by a network or any other communication means (where the use of the term means is used in the broadest sense possible).

[0066] In accordance with this embodiment of the present invention, an audio or audio-visual work is encoded into data that is later decoded to recreate the original audio or audio-visual work. Those of ordinary skill in the art should readily appreciate that the amount of data that represents a particular portion of the audio or audio-visual work can be transmitted, re-broadcast, and/or accessed from Storage Device 3100 in a time interval that is significantly less than the playback time interval of the particular portion. FIG. 8A shows the playback time of segments (Seg0, Seg1 . . . , SegN) of an original audio or audio-visual work, plotted along time axis 3001. The segments are encoded as data in accordance with methods that are well known to those of ordinary skill in the art, and the transmission times for the encoded data blocks (D0, D1, . . . , DN) which correspond to the segments (Seg0, Seg1, . . . , SegN) are shown along time-axis 3002. The time of receipt of the transmitted encoded data blocks (D0, D1, . . . , DN) are plotted along time axis 3003. As should be clear to those of ordinary skill in the art, the encoded data blocks (D0, D1, . . . , DN) are received after an arbitrary transmission delay through Network 3990. Lastly, after decoding, the segments (Seg0, Seg1, . . . , SegN) of the reconstructed audio or audio-visual work are plotted along time-axis 3004. Many methods are well known to those of ordinary skill in the art for encoding and decoding audio or audio-visual works.

[0067] Since, as discussed above, the transmission time of data that represents a particular portion of an audio or audio-visual work is generally smaller than the playback time interval of the particular portion, two or more audio or audio-visual works can be transmitted across a network by interleaving or Time-Division Multiplexing (TDM) the data representing the two audio or audio-visual works. Many methods are well known to those of ordinary skill in the art for interleaving and Time-Division Multiplexing data representing audio or audio-visual works during transmission across a network. In the preferred embodiment of the present invention, Time-Division Multiplexing is used to transmit data to Multicaster 3300. In particular, Work Streamer 3200 accesses data from Storage Device 3100, and outputs a TDM stream of data to Multicaster 3300.

[0068] In accordance with the preferred embodiment of the present invention, the audio or audio-visual work is divided into segments that are encoded as data for efficient storage and transmission. The encoded data representing an interval of the media work will be referred to as a “work-encoded-data-block.” FIG. 8B shows, in graphical form, a composition and transmission method utilized by Work Stream 3200 to form and transmit a TDM composite signal to Multicaster 3300 of embodiment 3000 shown in FIG. 7 of embodiment 3000. As shown in FIG. 8B, time axis 3010 shows the playback time of segments (Seg0, Seg1, . . . , Seg5) of the audio or audio-visual work being re-broadcast. Seg0 corresponds to the first segment of the audio or audio-visual work. Thus, time axis 3010 corresponds to a re-broadcast of the work that starts at the origin of the time axis (hence its designation as offset 0). Below time axis 3010 is shown the TDM transmit interval of a work-encoded-data-block that corresponds to the segment below which it appears (i.e., the time it takes to transmit the data). As discussed above, the time to transmit the corresponding work-encoded-data-block is less than the playback time of the segment. As further shown in FIG. 8B, time axis 3020 shows the playback time of segments (Seg5, Seg0, . . . , Seg4) of the audio or audio-visual work being re-broadcast. Seg0 corresponds to the first segment of the audio or audio-visual work. Thus, time axis 3020 corresponds to a re-broadcast of the work that starts offset from the origin of the time axis by one Re-broadcast Interval (“RBI”) (hence its designation as offset 1). Below time axis 3020 is shown the TDM transmit interval of a work-encoded-data-block which corresponds to the segment below which it appears (i.e., the time it takes to transmit the data). However, it is offset in time by an amount equal to the time it takes to transmit the work-encoded-data-block corresponding to segment SEG0 from the offset 0 data stream.

[0069] Thus, in accordance with the present invention, the re-broadcasts of the audio or audio-visual work are labeled: offset 0 stream, offset 1 stream, offset 2 stream, and so forth (along time axes 3010-3060) and the various offset streams represent re-broadcasts of the audio or audio-visual work at regular time intervals, which are referred to as Re-broadcast Intervals (“RBI”). That is, the starting times for the particular audio or audio-visual work being re-broadcast are offset at regular intervals, RBI, with the start of the re-broadcast of the audio or audio-visual work being denoted by Seg0, in each of the offset data streams shown in FIG. 8B).

[0070] In accordance with the preferred embodiment of the present invention, Work Streamer 3200 transmits composite signal 3065 (as Shown in FIG. 8B) to Multicaster 3500. As shown in FIG. 8B, composite signal 3065 is a TDM signal that is made up of TDM frames (this type of Time-Division Multiplexing is well known to those of ordinary skill in the art and many methods are well known to those of ordinary skill in the art for forming such a signal). As further shown in FIG. 8B, each TDM frame of composite signal 3065 comprises a work-encoded-data-block from each of the offset streams 0-5, wherein each of the work-encoded-data-blocks is offset in time for the time it takes to transmit a work-encoded-data-block. As one can readily appreciate, each TDM frame thereby comprises a work-encoded-data-block from each of the re-broadcasts in the appropriate time slot within the TDM frame. As should be well understood by those of ordinary skill in the art, the work-encoded-data-blocks are created by Work Streamer 3200 at the appropriate TDM transmit interval (as indicated on FIG. 8B) by sending appropriate signals to Storage Device 3100 at regular intervals. Note that the TDM transmission interval for each of re-broadcast offset streams 0-5 occurs at a unique time offset from the start of the TDM Frame. Advantageously, this enables multiple re-broadcasts of the audio or audio-visual work to be sent Multicaster 3300 in a TDM format. Further in accordance with the preferred embodiment of the present invention, the use of a TDM composite signal enables interleaved data access to Storage Device 3100 to provide greater performance in many storage devices of the type that are well known to those of ordinary skill in the art. It should also be noted that, even though it has been depicted in this manner for sake of ease of understanding the present invention in FIG. 8B, the transmission time required to send a work-encoded-data-block during a particular time slot may not consume the entire time slot interval.

[0071] It should be understood that although the preferred embodiment of the present invention utilizes a TDM composite signal, the invention is not thereby restricted and includes embodiments wherein other methods utilizing multiple streams and/or multiple storage devices, for example, one stream and perhaps one storage device for each re-broadcast, can be employed to send data from Work Streamer 3200 to Multicaster 3300. It should be clear that the TDM composite signal can have a number of channels that is bounded by the ability of the system to broadcast to clients without the clients noticing a lapse in transmission (of course this cannot account for nondeterministic delays in the network). If a larger number of channels is needed to handle the predetermined broadcasts than can be handled by the system without lapses, one could, for example, create multiple TDM composite signals to handle the extra load.

[0072] FIG. 9A shows a graph of location of a segment (offset from an origin) of the audio or audio-visual work being re-broadcast by embodiment 3000 shown in FIG. 7 as a function of time. As shown in FIG. 9A, during transmission of data at normal playback rates, the locations of segments of the audio or audio-visual work being broadcast as a function of time form a line having slope which represents the playback rate (a “normal” playback rate corresponding to a slope of 1) and an intercept on the time axis at the rebroadcast start time of the particular re-broadcast of the audio or audio-visual work. Data streams 3110-3140 shown in FIG. 9A have the same playback rates (and therefore the same slope), but are offset from one another since they have different re-broadcast start times. Note that at any particular time along the horizontal time axis multiple segments from different portions of the audio or audio-visual work are being re-broadcast simultaneously. This is seen by drawing a vertical line that intersects the horizontal time axis at a particular time.

[0073] As further shown in FIG. 9A, at 2 time units from the start of the re-broadcast of data stream 3110 (offset 0 data stream), client A0 sends a request to embodiment 3000 to begin viewing the particular audio or audio-visual work being re-broadcast. Client A0 must wait for the next re-broadcast to begin before receiving data (as shown in FIG. 9A, the next re-broadcast starts at the temporal location denoted by RBI). Thus, client A0 must wait 8 time units before receiving media or other data requested from data stream 3120 (offset 1 data stream). Similarly, if client A1 sends a request to begin viewing the particular audio or audio-visual work being re-broadcast 7 time units after the start of the re-broadcast of data stream 3110 (offset 0 data stream), client A1 has to wait 3 time units before receiving media or other data requested from data stream 3120 (offset 1 data stream).

[0074] FIG. 10 shows a block diagram of embodiment 4000 of the present invention that transitions asynchronously arriving requests to receive a particular audio or audio-visual work to synchronous re-broadcasts of the audio or audio-visual work. First, for ease of understanding the present invention, a general description of how embodiment 4000 operates is given with reference to FIG. 9A. In accordance with the present invention, embodiment 4000 causes the client to be joined to a data stream whose re-broadcast start time is closest (temporally) to the arrival of the client's request. Thus, in accordance with the present invention, for client A0, embodiment 4000 determines that the arrival time of the request to begin viewing is closest to the re-broadcast start time of data stream 3110 (note that the re-broadcast time of data stream 3110 has already occurred). Embodiment 4000 then begins re-broadcasting data to client A0 at 5/3 the normal rate, i.e., at an accelerated rate. In accordance with the present invention, transmission at the accelerated rate enables client A0 to “catch up” to the normal re-broadcast location in the audio or audio-visual work 5 time units after the re-broadcast start time of data stream 3110. In response to receiving data at the accelerated rate, the client (or the client's server) automatically initiates playback at an appropriate rate to keep its arrival or capture buffer from overflowing, for example, in accordance with aspects of the present invention that have been described in detail above. In an alternative embodiment of the present invention, instead of having the client determine the accelerated rate required by its playback system to avoid an overflow of the data received, the accelerated rate is transmitted to the client by embodiment 4000 when transmission is starts.

[0075] Next, in accordance with the present invention, whenever embodiment 4000 determines that the stream of data being re-broadcast to client A0 relates to the same playback position as data stream 3110, embodiment 4000 sends client A0 data at the normal rate from data stream 3110. Advantageously, in accordance with the present invention, overhead on embodiment 3000, and the corresponding components of embodiment 4000, is reduced since, as will be explained in detail below, the client now receives data from Multicaster 4300 and no additional accesses to Storage Device 4100 or Work Streamer 4200 are required to provide data to the client. Additionally, as will be described in detail below, once the transition to the offset stream has occurred, the client no longer consumes resources Variable Rate Broadcaster 4600.

[0076] In a similar manner to that described above, in accordance with the present invention, for client A1, embodiment 4000 determines that the arrival time of the request to begin viewing is closest to the re-broadcast start of data stream 3120 (note that the re-broadcast time of data stream 3120 has yet to occur). Embodiment 4000 then begins re-broadcasting data to client A1 at 5/8 the normal rate, i.e., at a reduced rate. In accordance with the present invention, transmission at the reduced rate enables client A1 to reach the normal re-broadcast location in the audio or audio-visual work 5 time units after the re-broadcast start time of data stream 3120. In response to receiving data at the reduced rate, the client (or the client's server) automatically initiates playback at an appropriate rate to keep its arrival or capture buffer from emptying, for example, in accordance with aspects of the present invention that have been described in detail above. In an alternative embodiment of the present invention, instead of having the client determine the reduced rate required by its playback system to avoid emptying, the reduced rate is transmitted to the client by embodiment 4000 when transmission is started.

[0077] Next, in accordance with the present invention, whenever system 4000 determines that the stream of data being re-broadcast to client A1 relates to the same playback position as data stream 3120, embodiment 4000 sends client A1 data at the normal rate from stream 3120. Advantageously, in accordance with the present invention, overhead on embodiment 3000, and the corresponding components of embodiment 4000, is reduced since, as will be explained in detail below, the client now receives data from Multicaster 4300 and no additional accesses to Storage Device 4100 or Work Streamer 4200 are required to provide data to the client. Additionally, as will be described in detail below, once the transition to the offset stream has occurred, the client no longer consumes resources Variable Rate Broadcaster 4600.

[0078] We now return to a detailed description of embodiment 4000. As shown in FIG. 10, Storage Device 4100 is a storage device of a type which is well known to those of ordinary skill in the art. Storage Device 4100 stores a representation (preferably a digital representation or any representation that can be converted to a digital representation in accordance with methods which are well known to those of ordinary skill in the art) of an audio or audio-visual work or data of interest to a user (such as a stream of stock quotes, market data, advertisements, and so forth). Storage Device 4100 receives, as input: (a) data requests from Work Streamer 4200; data requests from Variable Rate Broadcaster 4600. Storage Device 4100 provides, as output, the data requested.

[0079] As further shown in FIG. 10, Work Streamer 4200 receives as input: (a) a code (for example, a number) which represents a desired Re-broadcast Interval (“RBI”) from Re-broadcast Interval Determiner 4700; (b) a code (for example, a number) which represents a desired number of Time-Division Multiplexed (TDM) channels; (c) a code (for example, a number) which represents the duration of the audio or audio visual work being re-broadcast; and (d) data transmitted from Storage Device 4100. Work Streamer 4200 produces, as output: (a) a Time-Division Multiplexed composite signal as described above (this is applied as input to Multicaster 4300) and (b) a stream of information that provides the playback position and time offset of each time-offset re-broadcast stream of the work (this is applied as input to Slope/Rate Determiner 4400).

[0080] As still further shown in FIG. 10, Re-broadcast Interval Determiner (“RBID”) 4700 receives, as input, (a) a code (for example, a number) which represents the duration of an audio or audio/visual work being re-broadcast and (b) a code (for example, a number) that represents the number of re-broadcast offset channels, and produces, as output, data representing the duration of the re-broadcast interval (“RBI”). In accordance with the present invention, Re-broadcast Interval Determiner 4700 computes the RBI by applying one of a number of formulas. In the preferred embodiment of the present invention, the following formula is used:

[0081] RBI=Duration of audio or audio-visual work/No. of re-broadcast offset channels  (6)

[0082] As yet still further shown in FIG. 10, Slope Rate Determiner (“SRD”) 4400 receives as input: (a) data representing start times for each offset data stream of the audio or audio visual work being re-broadcast from Work Streamer 4200; (b) arrival times and client identification information from Request Processor 4500; and (c) a set of parameters representing maximum allowable Time-Scale Modification rates (or slopes). SRD 4400 produces as output: (a) client identification information for the client requesting the data (applied as input to Variable Rate Broadcaster 4600 “VRB 4600” and Multicaster 4300); (b) an identification of the re-broadcast offset data stream the client will be synchronized or merged with (applied as input to VRB 4600); (c) an indication of the time it will take before the synchronization or merge takes place (“duration to intercept”) (applied as input to VRB 4600 and Multicaster 4300); and (d) a slope, which represents the playback rate (this slope or playback rate is applied as input to VRB 4600). In accordance with the present invention, SRD 4400 determines the re-broadcast offset data stream whose start time is temporally closest to the arrival time of the client's request by computing the distance forward and backward in time to the previous offset stream start time and the next offset stream start time (with respect to the arrival time), and choosing the smaller of the forward and backward times. Next, SRD 4400 computes a client playback slope that is greater than 1.0 if “catching-up” to a future playback intercept position in an offset stream already started, or a client playback slope that is less than 1.0 to “slow-down” to a future playback intercept position in an offset stream which will start in the future. The actual slope can be determined by a number of factors such as the utilization of VRB 4600 (if a higher slope is used, there is a greater load since data must be sent faster), and the maximum allowable Time-Scale Modification rate. In most cases slope values will be between ½ and 2.0, and can be calculated: (a) by computing a desired playback position change per unit time; (b) by accessing a pre-computed look-up table; or (c) any other method of choosing a reasonable slope, such as, by client input relating to the speed of the “catch-up.” The “duration to intercept” is calculated by subtracting the time that data transmission to the client is initiated from the time interval at which the playback positions of VRB 4600 and the target offset stream are identical. The “duration to intercept” information is used to signal VRB 4600 when it must end transmission to the client and to signal Multicaster 4300 when it must initiate transmission of the appropriate offset stream.

[0083] As yet again still further shown in FIG. 10, VRB 4600 receives as input: (a) data from Storage Device 4100; (b) a slope or playback rate from SRD 4400; (c) client identification information for the client requesting the data from SRD 4400; (d) an identification of the re-broadcast offset data stream the client will be synchronized or merged with; and (e) “duration to intercept” from SRD 4400. VRB 4600 obtains the specified data received from Storage Device 4100 and broadcasts it to the identified client at the specified rate for an amount of time equal to the “duration to intercept” and then stops sending data for that client. VRB 4600 produces as output a stream of data sent to the identified client via a network such as the Internet or Intranet and so forth.

[0084] As yet still further shown in FIG. 10, Multicaster 4300 receives as input: (a) a data stream (the Time-Division Multiplexed composite signal) from Work Streamer 4200; (b) client information (control and destination) from Request processor 4500; (c) client identification information for the client requesting the data from SRD 4400; and (d) “duration to intercept” information from SRD 4400. Multicaster 4300 produces, as output, data (for example, message packets) directed toward particular clients for clients for re-broadcast on a network such as the Internet, WAN, LAN, etc. In accordance with the present invention, Multicaster 4300 manages a list of all clients that should receive data from particular portions of the TDM composite signal in accordance with any one of a number of methods which are well known to those of ordinary skill in the art. Then, whenever the particular portion of data in the TDM composite signal is received from Work Streamer 4200, Multicaster 4300 sends the particular portion of data to all clients (recipients) in the list who are to receive the particular portion of data (also known as multicasting). Many methods for broadcasting a portion of data from a data stream (for example, a Time-Division Multiplexed composite signal) to multiple recipients are well known to those of ordinary skill in the art. Control information from Request Processor 4500 are used in accordance with methods that are well known to those of ordinary skill in the art to modify the list of recipients, for example, to add a recipient, or to remove a recipient from the list of destinations when the recipient no longer desires to receive data from the server. The “duration to intercept” and client information from SRD 4400 is used to notify Multicaster 4300 when clients previously receiving data from VRB 4600 should begin receiving data from one of the offset streams.

[0085] Lastly, Request Processor 4500 receives, as input, requests for data from clients connected via a network (for example, an Internet, WAN, LAN, or the like). In response, Request Processor 4500 produces, as output, information identifying the client and the appropriate re-broadcast control information such as, for example, “request data that is identified by an appropriate data identifier,” “disconnect,” and other messages that are used to obtain data from embodiment 4000. It should be clear to those of ordinary skill in the art, that such information identifying the client and appropriate re-broadcast control information may be obtained: (a) by dialogs between the client and Request Processor 4500 in accordance any one of many methods that are well known to those of ordinary skill in the art including, without limitation, by use of forms that are contained on web pages that are transmitted to the client over a network in accordance any one of the many methods that are well known to those of ordinary skill in the art.

[0086] Although FIG. 10 shows embodiment 4000 to be comprised of separate modules, in a preferred embodiment, the modules are embodied as software programs or modules which run on a general purpose computer such as, for example, a personal computer. It should be well known to one of ordinary skill in the art, in light of the detailed description above, how to implement these programs or modules in software.

[0087] Conversely, components of embodiment 4000 may exist in separate locations connected to one another by a network or any other communication means (where the use of the term means is used in the broadest sense possible).

[0088] To better understand the operation of embodiment 4000 described above, FIG. 9B shows a graph of work-encoded-data-block number (offset from an origin) of the audio or audio-visual work being re-broadcast by embodiment 4000 as function of time. As shown in FIG. 9B, during transmission of data at normal playback rates, the work-encoded-data-blocks of the audio or audio-visual work being re-broadcast as a function of time, form a line having slope 1 and an intercept on the time axis at the re-broadcast start time of the particular broadcast of the work. As further shown in FIG. 9B, data streams 3110 and 3120 are offset from one another, i.e., they are data streams having different “re-broadcast start-times.” However, data streams 3110 and 3120 have the same playback rate, i.e., the same slope in FIG. 9B, but different intercepts on the time axis corresponding to their different start times. As discussed above, streams transmitted at a normal rate have slope 1.

[0089] As further shown in FIG. 9B, the work-encoded-data-blocks sent by VRB 4600 of embodiment 4000 are identical to the work-encoded-data-blocks sent by Multicaster 4300 of embodiment 4000, but are simply broadcast with a different time interval between the work-encoded-data-blocks. This means that VRB 4600 sends the same work-encoded-data-blocks that Multicaster 4300 sends, but adjusts the time interval between transmissions of the work-encoded-data-blocks in order to “catch-up to” or “wait-for” the stream of data blocks sent by Multicaster 4300. If the client request is received between (n)RBI and (n+½)RBI (less than the half-way point, in time, between the nth and the (n+1)st re-broadcast start time), the inter-transmission interval is shortened to catch-up to an intersection point in the previous offset stream (note the data transmitted for path 3111 has the same work-encoded-data-blocks as path 3110, but spaced closer together in time). If the client request is received between (n+½)RBI and (n+1)RBI (more than the half-way point, in time, between the nth and the (n+1)st re-broadcast start time), the inter-transmission interval is lengthened to wait for an intersection point with the next offset stream (note the data transmitted for path 3121 has the same work-encoded-data-blocks as path 3120, but spaced further apart in time). Note that, in accordance with the present invention, only the initial portion of the audio or audio-visual work is broadcast by VRB 4600, and thus VRB 4600 can cache the work-encoded-data-blocks from the initial portion of the work to further reduce the number of accesses to Storage Device 4100. There are many methods and apparatus that are well known to those of ordinary skill in the art for caching data, such as, for example, SRAM, DRAM, or small capacity hard disks.

[0090] Then, in accordance with the present invention, once embodiment 4000 (or the transmitting server) determines that the stream of data being broadcast to client A1 is accessing the same playback position during the same time interval as stream 3120, the server sends the client data at the normal rate from stream 3120 and the overhead on the media server is reduced. In the preferred embodiment the duration to intercept is used to identify the time at which the stream from VRB 4600 and Multicaster 4300 will intercept and when the responsibility of transmitting data to the client should transition from VRB 4600 to Multicaster 4300.

[0091] Although aspects of the present invention have been described in the context of aligning or synchronizing to one of several, offset, re-broadcast data streams, it should be clear that the present invention is not limited to time alignment of re-broadcasted works. In fact, embodiments of the present invention may also be used to align or synchronize with (catch up), for example, live broadcasts by storing or time shifting an audio or audio-visual work that is broadcast only once. For example, in digital VCRs or televisions that contain digital storage for spooling live broadcasts, a user may watch a live broadcast and invoke a “Pause” function (by, for example, pressing a “pause and record” button) to stop playback and initiate recording of the one-time broadcast audio or audio-visual work. In response, the one-time broadcast audio or audio-visual work is recorded from the point where the Pause function was invoked to the end of the audio or audio-visual work. As should be clear, this enables a user to turn to other tasks. After the user is ready to return to the work, playback is resumed at the location where the “Pause” was initiated by playing the recorded copy of the one-time broadcast. This playback is said to be “time-shifted” since the playback time differs from the one-time broadcast time. In prior art devices, there is no mechanism to catch up to the one-time broadcast without deleting or skipping some portion of the time-shifted copy of the audio and/or audio-visual work in the broadcast. However, embodiments of the present invention, can be used to catch-up to the live one-time broadcast by computing the playback rate required to catch-up in a predetermined interval, such as a commercial break, program boundary, or the like. In this manner users watching a time-shifted version can “catch-up” to a live broadcast after they have paused their viewing devices.

[0092] FIG. 9C shows a graph of position (offset from an origin) of an audio or audio-visual work being received by a media playback device that incorporates storage of the audio or audio-visual work, such as, for example a digital VCR, hard-disk based VCR, and the like. As shown in FIG. 9C, a one-time live broadcast (4001) is being viewed as it is broadcast. At time Tp, the user invokes the Pause function. As previously described, the one-time live broadcast is recorded after invoking the Pause function. At time Tr, the user resumes viewing at the same location in the work where the Pause function was invoked. However, the user is behind the live broadcast. Using the inventive method and apparatus previously described with respect to embodiment 4000, the user specifies the amount of time desired to transition back to the one-time live broadcast (received by Request Processor 4500), and apparatus, similar to Slope/Rate Determiner 4400, computes a Time-Scale Modification Rate, or Playback Rate, that will transition the user to the one-time live broadcast during the specified interval. The intercept interval computed by embodiment 4000 determines the time at which the media playback device may discontinue recording of the one-time live broadcast, since after the intercept interval, the user will be viewing the one-time live broadcast as it is received. As shown in FIG. 9C, time Tv marks the time at which the user will again be viewing the live broadcast. The time interval from Tr to Tv defines the transition period during which the user will be watching a Time-Scale compressed (or speeded-up) version of the recorded material. The time interval from Tp to Tv defines the interval of the one-time live broadcast which must be recorded in order to provide a seamless transition to the live-broadcast from a time-shifted viewing reference.

[0093] Note that upon intersecting with the one-time live broadcast, there is no longer a need to continue recording the work, and this process is stopped. The ability of embodiment 4000 to merge with or “catch-up” to a one-time live broadcast of a work from a time-shifted copy of the work that has been recorded significantly reduces the amount of the work which must be stored or recorded. This reduction further reduces the required storage resources required.

[0094] In accordance with a farther aspect of the present invention, system overhead for serving requests from clients that arrive during intervals between the start of re-broadcasts of a particular audio or audio-visual work is further reduced. In accordance with this further aspect of the present invention, portions of the audio or audio-visual work being broadcast are Time-Scale Modified at two rates: one rate is faster than normal speed and one rate is slower than normal speed. These slow-rate and fast-rate broadcast portions of the audio or audio-visual work are re-broadcast during an interval from the start of re-broadcast of the work to a point X during the broadcasting of the work, which point X is a function of the re-broadcast interval and the amount of Time-Scale Modification performed. These portions will be referred to as Time-Scaled Leaders. FIG. 11A shows a graph of location (offset from an origin) of an audio or audio-visual work being re-broadcast by embodiment 5000 shown in FIG. 12 as a flnction of time in accordance with the further aspect of the present invention. As shown in FIG. 11A, embodiment 5000 (TSM System 5400 of embodiment 5000 shown in FIG. 12) time compresses the first 10 time units of the audio or audio-visual work and creates a new data stream 3210 which has duration 5 units and a playback rate of 2. Note that only 10 time units of the beginning of the original audio or audio-visual work are time-scale compressed. Next, as shown in FIG. 11A, embodiment 5000 (TSM System 5400 of embodiment 5000 shown in FIG. 12) time-expands the first 5 time units of the work and creates a new data stream 3220 which has duration 10 units and playback rate of ½. Note that only 5 time units of the beginning of the original audio or audio-visual work are time-scale expanded. As further shown in FIG. 11A, playback of either of these two data segments 3210 and 3220 may begin at the midpoint of the interval between re-broadcast start times (RBI/2), and, upon reaching the end of each Time-Scale Modified data stream, the client will be at the same segment location of the audio or audio-visual work being re-broadcast on an earlier or later offset data stream, respectively. In the preferred embodiment, segments (labeled 3211, 3212) of the single time-scale compressed leader 3210 are used to merge with the previous offset stream from starting times between (n)RBI and (n)(RBI/2) as shown in FIG. 11A. Similarly, segments (labeled 3221, 3222) of the single time-scale expanded leader 3220 are used to merge with the next offset stream from starting times between (n)(RBI/2) and RBI(n+1) as shown in FIG. 11A.

[0095] As is readily apparent from FIG. 11A, in accordance with the present invention, further, smaller time-scale compressed and time-scale expanded portions of the audio or audio-visual work are re-broadcast from times between the midpoint of the re-broadcast interval, and merge with the offset streams. In the preferred embodiment segments of the time-scale compressed leader and segments of the time-scale expanded leader are broadcast from starting times other than the offset stream start-times and merge with the offset streams. The interval between re-broadcasts of the Time-Scale Modified Leaders is Leader Re-broadcast Interval (LRBI), which LRBI can be selected by embodiment 5000. In accordance with a preferred embodiment of the present invention, as shown in FIG. 11A, re-broadcasts of the time-scale compressed leader and time-scale expanded leader may be accomplished utilizing the technique of Time-Division Multiplexing for further efficiency.

[0096] Advantageously, in accordance with this aspect of the present invention, there is no need to compute playback rates, and a media server needs only: (a) to select a Time-Scale Modified Leader to send to the client and (b) to manage a transition from the Time-Scale Modified Leader to a data stream being transmitted at normal speed when appropriate. Thus, in accordance with this aspect of the present invention, SRD 4400 and VRB 4600 of embodiment 4000 are replaced with a Time-Scaled Leader Duration Determiner, Time-Scale Modification apparatus, and apparatus for streaming and multicasting the Time-Scale Modified Leaders. In accordance with the preferred embodiment of the present invention, the Time-Scale Modified Leaders are re-broadcast at regular intervals separated in time by an amount LRBI.

[0097] Although the inventive technique has been described using two time-scale modified leaders and segments thereof, the invention is not thusly limited and embodiments using leaders with unique TSM rates (playback rates) are possible. In addition, multiple TSM leaders with different start times and different TSM rates may share a common intercept point in the work.

[0098] FIG. 11B shows, in graphical form, encoding portions of a Time-Scale Modified audio or audio-visual work to form Time-Scale Modified Leaders. Playback time of segments (Seg0, Seg1, . . . , SegN) of an original audio or audio visual work are plotted along time axis 4037. These segments are encoded as data in accordance with methods that are well known to those of ordinary skill in the are, and the transmission times for work-encoded-data-blocks (D0, D1, . . . , DN) which correspond to the segments (Seg0, Seg1, . . . , SegN) are shown along time axis 4039. Playback time of segments (Seg0, Seg1, . . . , SegN) for a time-scale compressed leader (compresses by a factor of 2) are shown along time-axis 4041. These segments are encoded as data, and the transmission times for work-encoded-data-blocks (D0, D1, . . . , DN) which correspond to the segments (Seg0-Seg1, Seg2-Seg3, . . . ) are shown along time axis 4043. Lastly, playback time of segments (Seg0, Seg1, . . . , SegN) for a time-scale expanded leader (expanded by a factor of 2) are shown along time-axis 4045. These segments are encoded as data, and the transmission times for work-encoded-data-blocks (D0, D1, . . . , DN) which correspond to the segments (Seg0/2, Seg0/2, Seg1/2, Seg1/2, . . . ) are shown along time axis 4047.

[0099] FIG. 12 shows a block diagram of embodiment 5000 of the present invention which: (a) transmits Time-Scale Modified Leaders; (b) joins re-broadcast offset streams of an audio or audio-visual work; and (c) transmits offset streams of an audio or audio-visual work. As shown in FIG. 12, Re-broadcast Interval Determiner (RBID) 5700 receives, as input: (a) a code (for example, a number) which represents the duration of an audio or audio-visual work being re-broadcast and (b) a code (for example, a number) that represents the number of re-broadcast offset channels. RBID 5700 produces, as output, data representing the duration of the re-broadcast interval (“RBI”). The RBI is applied as input to Work Streamer 5200, Leader Re-broadcast Interval Determiner 5710, and Time-Scaled Leader Duration Determiner (“TSLDD”) 5600. In accordance with the present invention, RBID 5700 computes the RBI by applying one of a number of formulas. In the preferred embodiment, the following formula is used:

[0100] RBI=Duration of audio or audio-visual work/No. of re-broadcast offset channels  (7)

[0101] Work Streamer 5200 and Multicaster 5300 are identical to Work Streamer 4200 and Multicaster 4300, respectively, which were described above with respect to embodiment 4000 shown in FIG. 10.

[0102] As further shown in FIG. 12, TSLDD 5600 receives as input: (a) RBI (from RBID 5700); (b) a user defined parameter representing the time-scale compression (or speed-up) rate to use; and (c) a user defined parameter representing the time-scale expansion (or slow-down) rate to use. In response, TSLDD 5600 produces, as output, the maximum time interval of the input audio or audio-visual work that will be required for creation of time-scale-compressed leaders and time-scale expanded leaders (applied as input to TSM System 5400). TSLDD 5600 computes the time interval of the original audio or audio-visual work that will be time-scale compressed to form a time-scale compressed leader and the time interval of the original audio or audio-visual work that will be time-scale expanded to form a time-scale expanded leader by applying the following formulas:

[0103] Speed-up:

[0104] Tdo=(I/2)(Speed/(Speed−1))  (8)

[0105] where: Tdo=Time Interval of the original audio or audio-visual work to be time-scale compressed; Speed=speed-up factor (i.e.>1)=1/time-compression factor; and I=Re-broadcast interval.

[0106] Slow-down:

[0107] Tdo=(I/2)(Speed/(1−Speed))  (9)

[0108] where: Tdo=Time Interval of the original audio or audio-visual work to be time-scale expanded; Speed=slow-down factor (i.e.<1)=1/time-expansion factor; and I=Re-broadcast interval.

[0109] As one can readily appreciate from the above, for speed-up by a factor of 2 (i.e., time-compression by ½) and slow-down by a factor of ½ (i.e., time-expansion by 2), the time-compressed leader is obtained from a segment of the original audio or audio-visual work which starts at the beginning of the audio or audio-visual work and has a time interval equal to the re-broadcast interval. The time-expanded leader is obtained from a segment of the original audio or audio-visual work which starts at the beginning of the audio or audio-visual work and has a time interval equal to ½ the re-broadcast interval. This can also be understood as described above with respect to FIG. 11A.

[0110] As shown in FIG. 12, Time-Scale Modification System (TSMS) 5400 receives as input: (a) data from Storage Device 5100 representing the original audio or audio-visual work; (b) the time interval of the original audio or audio-visual work required to generate time-scale compressed leaders (from TSLDD 5600); (c) the time interval of the original audio or audio-visual work required to generate a time-scale expanded leaders (from TSLDD 5600); (d) the speed factor for time-scale compression (from TSLDD 5600); and (e) the speed factor for time-scale expansion (from TSLDD 5600). TSMS 5400 produces as output (a) a time-scale compressed leader; and (b) a time-scale expanded leader. TSMS 5400 time-scale compresses (at the specified speed factor) the specified duration of the original work to produce the time-scale compressed leader. Similarly, TSMS 5400 time-scale expands (at the specified speed factor) the specified duration of the original work to produce the time-scale expanded leader. In a preferred embodiment of the present invention, the time-scale-compressed leader and the time-scale expanded leader are stored in Storage Device 5100.

[0111] Storage Device 5100 is a storage device of a type which is well known to those of ordinary skill in the art. Storage Device 5100 stores a representation (preferably a digital representation or any representation that can be converted to a digital representation in accordance with methods which are well known to those of ordinary skill in the art) of an audio or audio-visual work or data of interest to a user (such as a stream of stock quotes, market data, advertisements, and so forth) and Time-Scale Modified Leaders.

[0112] As shown in FIG. 12, Request Processor (RP) 5500 receives, as input, requests for data from clients connected via a network (for example, an Internet, WAN, LAN, or the like). In response, Request Processor 5500 produces, as output, information identifying the client and the appropriate re-broadcast control information such as, for example, “request for data that is identified by an appropriate data identifier,” “disconnect,” and other messages that are used to obtain data from embodiment 5000. It should be clear to those of ordinary skill in the art, that such information identifying the client and appropriate re-broadcast control information may be obtained: (a) by dialogs between the client and Request Processor 4500 in accordance any one of many methods that are well known to those of ordinary skill in the art including, without limitation, by use of forms that are contained on web pages that are transmitted to the client over a network in accordance any one of the many methods that are well known to those of ordinary skill in the art. Output from RP 5500 is applied as input to Stream Assignment System (SAS) 5550.

[0113] As shown in FIG. 12, SAS 5550 receives, as input: (a) information from RP 5500; (b) leader-offset-stream information (described in detail below) from TSCL Streamer 5210; (c) leader-offset-stream information (described in detail below) from TSEL Streamer 5220; and (d) information (described in detail below) from LRBID 5710. SAS 5550 produces, as output, control information which is received by Multicaster 5300, TSCL Multicaster 5310, and TSEL Multicaster 5320. In accordance with this embodiment of the present invention, SAS 5550 first determines a temporally closest leader-offset-stream by computing distances, forward and backward, in time from the arrival time of a client's request to view an audio or audio-visual work, to the previous Time-Scale Modified Leader-offset-stream start time and the next Time-Scale Modified Leader-offset-stream start time, and choosing the smaller of the two as the temporally closest leader-offset-stream. This can be performed by either of two methods: (a) by monitoring information output from TSCL Streamer 5210 and TSEL Streamer 5220 or (b) by computing the start times for the leaders from information provided by LRBID 5710. In accordance with this embodiment of the present invention, SAS 5550 then produces, as output, information that directs either TSCL Multicaster 5310 or TSEL Multicaster 5320 to add the requesting client to the list of destinations for the appropriate Time-Scale Modified Leader offset stream segments being re-broadcast. SAS 5550 also sends information to Multicaster 5300 and either TSCL Multicaster 5310 or TSEL Multicaster 5320 which information conveys client identification and control information and the “intercept-time” for the corresponding Time-Scale Modified Leader offset stream to an offset stream of the original audio or audio-visual work. In response to the intercept information, TSCL Multicaster 5310 and TSEL Multicaster 5320 note the intercept time and schedule the deletion of the requesting client from the list of multicast recipients of that TSM Leader offset stream after the intercept time. Additionally, and in response to the intercept information, Multicaster 5300 notes the intercept time and schedules the addition of the requesting client to the list of multicast recipients of that offset stream after the intercept time.

[0114] As shown in FIG. 12, Time-Scale Expanded Leader Streamer 5220 receives, as input: (a) a code (for example, a number) which represents a desired Leader Re-broadcast Interval (“LRBI”) from Leader Re-broadcast Interval Determiner 5710; (b) a code (for example, a number) which represents a desired number of Time-Division Multiplexed (TDM) channels for the Time-Scale Expanded Leader from Leader Re-broadcast Interval Determiner 5710; (c) a code (for example, a number) which represents the duration of the leader being re-broadcast from Leader Re-broadcast Interval Determiner 5710 (alternatively, this information could have come directly from TSLDD 5600); (d) the start times of the re-broadcast offset streams of the original audio or audio-visual work from Leader Re-broadcast Interval Determiner 5710; and (e) data for the audio or audio-visual work from Storage Device 5100. Time-Scale Expanded Leader Streamer 5220 produces, as output: (a) the Time-Division Multiplexed composite signal of leader segments in a manner similar to that described above for Work Streamer 4200 (applied as input to TSEL Multicaster 5320) and (b) a stream of information giving the playback position and time-offset for each time-offset re-broadcast stream of the Time-Scale Expanded Leader (applied as input to SAS 5550).

[0115] As shown in FIG. 12, Time-Scale Compressed Leader Streamer 5210 receives, as input: (a) a code (for example, a number) which represents a desired Leader Re-broadcast Interval (LRBI) from Leader Re-broadcast Interval Determiner 5710; (b) a code (for example, a number) which represents a desired number of Time-Division Multiplexed (TDM) channels for the Time-Scale Compressed Leader from Leader Re-broadcast Interval Determiner 5710; (c) a code (for example, a number) which represents the duration of the leader being re-broadcast from Leader Re-broadcast Interval Determiner 5710 (alternatively, this information could have come directly from TSLDD 5600); (d) the start times of the re-broadcast offset streams of the original audio or audio-visual work from Leader Re-broadcast Interval Determiner 5710; and (e) data for the audio or audio-visual work from Storage Device 5100. Time-Scale Compressed Leader Streamer 5210 produces, as output: (a) the Time-Division Multiplexed composite signal of leader segments in a manner similar to that described above for Work Streamer 4200 (applied as input to TSCL Multicaster 5310) and (b) a stream of information giving the playback position and time-offset for each time-offset re-broadcast stream of the Time-Scale Compressed Leader (applied as input to SAS 5550).

[0116] As shown in FIG. 12, Leader Re-broadcast Interval Determiner (LRBID) 5710 receives, as input: (a) a code (for example, a number) which represents the duration of the time-scale compressed and time-scale expanded leaders from TSLDD 5600; (b) a code (for example, a number) which represents the number of leader re-broadcast offset channels Re-broadcast Interval Determiner 5700; and (c) a code (for example, a number) which represents the RBI from RBID 5700. LRBID 5710 produces, as output, data which represents the duration of the Leader Re-broadcast Interval (“LRBI”) (applied as input to TSCL Streamer 5210 and TSEL Streamer 5220). Leader Re-broadcast Interval Determiner 5710 computes the LRBI by applying the following formula:

[0117] LRBI=RBIof audio or audio-visual work/No. of leader re-broadcast offset channels  (10)

[0118] Note that the greater the number of leader re-broadcast offset channels, the shorter the LRBI, and the less time a requesting client must wait to begin receiving media data from embodiment 5000.

[0119] As shown in FIG. 12, TSCL Multicaster 5310 receives, as input: (a) a composite signal from TSCL Streamer 5210 and (b) client information (for example, control and destination) from SAS 5550. Likewise, as shown in FIG. 12, TSEL Multicaster 5320 receives, as input: (a) a composite signal from TSEL Streamer 5220 and (b) client information (for example, control and destination) from SAS 5550. Then, in accordance with the present invention, TSCL Multicaster 5310 and TSEL Multicaster 5320 produce, as output, data (for example, message packets) directed toward particular clients for re-broadcast on a network such as the Internet, WAN, LAN, etc. In accordance with the present invention, TSCL Multicaster 5310 and TSEL Multicaster 5320 each manages a list of all clients that should receive data from particular portions of the TDM composite signal in accordance with any one of a number of methods which are well known to those of ordinary skill in the art. Then, whenever the particular portion of data in the TDM composite signal is received from TSCL Streamer 5210 and TSEL Streamer 5220, respectively, TSCL Multicaster 5310 and TSEL Multicaster 5320, respectively, sends the particular portion of data to all clients (recipients) in the list who are to receive the particular portion of data (also known as multicasting). Many methods for broadcasting a portion of data from a data stream (for example, a Time-Division Multiplexed composite signal) to multiple recipients are well known to those of ordinary skill in the art. Control information from SAS 5550 is used in accordance with methods that are well known to those of ordinary skill in the art to modify the list of recipients, for example, to add a recipient, or to remove a recipient from the list of destinations when the recipient no longer desires to receive data from the server. Lastly, whenever the data stream for a leader merges with a re-broadcast offset stream, the client is removed from the list of recipients.

[0120] Embodiment 5000 has been described in detail above using separate components for ease of understanding the present invention, however, it should be clear to those of ordinary skill in the art that many of the components perform similar functions to their counterparts in embodiment 4000. Further, many of these corresponding components may be combined without loss of functionality. Still further, the intercept intervals in embodiment 5000 of the present invention follow a regular and periodic pattern which advantageously simplifies calculations of slope or playback rate and can be easily implemented using standard techniques such as lookup tables, count-down timers, and the like, all of which are well known to those of ordinary skill in the art.

[0121] Conversely, components of embodiment 5000 may exist in separate locations connected to one another via a network or any other communication means (where the use of the term means is used in the broadest sense possible).

[0122] Although FIG. 12 shows embodiment 5000 to be comprised of separate modules, in a preferred embodiment, the modules are embodied as software programs or modules which run on a general purpose computer such as, for example, a personal computer. It should be well known to one of ordinary skill in the art, in light of the detailed description above, how to implement these programs or modules in software.

[0123] Those skilled in the art will recognize that the foregoing description has been presented for the sake of illustration and description only. As such, it is not intended to be exhaustive or to limit the invention to the precise form disclosed.

[0124] Advantageously, embodiments of the present invention may be used to distribute Movies, Documentaries, or other audio and/or audio-visual works electronically, such as, for example, pay-per-view programs, video rental and the like. For example, although the distribution was described using networks, it should be understood that the term network is used in the broadest sense of the word and includes local distribution over cable, for example, a hotel distribution system, distribution over satellite, distribution over the public airwaves where terminals are used in accordance with well known methods to authorize client access. It should also be clear that Request Processor 5550 can include functionality (in accordance with methods that are well known to those of ordinary skill in the art) to charge money for receiving works such as movies, sporting events and so forth.

[0125] For example, those of ordinary skill in the art should readily understand that whenever the term “Internet” is used, the present invention also includes use with any non-deterministic delay network. As such, embodiments of the present invention include and relate to the world wide web, the Internet, intranets, local area networks (“LANs”), wide area networks (“WANs”), combinations of these transmission media, equivalents of these transmission media, and so forth.

[0126] In addition, it should be clear that embodiments of the present invention may be included as parts of search engines used to access streaming media such as, for example, audio or audio-visual works over the Internet.

[0127] In further addition, it should be understood that although embodiments of the present invention were described where the audio or audio-visual works were applied as input to playback systems, the present invention is not limited to the use of a playback system. It is within the spirit of the present invention that embodiments of the present invention include embodiments where the playback system is replaced by a distribution system, which distribution system is any device that can receive digital audio or audio-visual works and re-distribute them to one or more other systems that replay or re-distribute audio or audio-visual works. In such embodiments, the playback system is replaced by any one of a number of distribution applications and systems which are well known to those of ordinary skill in the art that further distribute the audio or audio-visual work. It should be understood that the devices that ultimately receive the re-distributed data can be “dumb” devices that lack the ability to perform Time-Scale modification or “smart” devices that can perform Time-Scale Modification.

[0128] Although the present invention has been described using Time-Scale Modified Leaders to catch-up or slow-down to a re-broadcast offset stream of a media work played at a normal playback rate (slope=1), the present invention is not thusly limited. For example, further embodiments of the present invention can be utilized to enable clients to merge with time-scale compressed versions of a work (slope>1), time-scale expanded versions of a work (slope<1), or to enable clients to migrate from a time-scale modified version of a work at one particular playback speed to a time-scale modified version of the same work with a different playback speed. In accordance with the present invention, this is accomplished by providing transitions from one data stream to another at specific intercept points, or by employing time-scale modified leaders to transition between versions of a work with different playback speeds.

[0129] In accordance with the present invention, these embodiments are fabricated using embodiment 5000 described above, with a modification to SAS 5550. The modification enables SAS 5550 to compute the temporally closest stream with the requested time-scale (i.e., playback-rate) requested by the client at any point during playback.

[0130] FIG. 13 shows a graph of location (offset from an origin) in normal and Time-Scale Modified versions of offset re-broadcasts of an audio or audio-visual work versus time on the horizontal axis. As shown in FIG. 13, nine (9) offset data streams are being re-broadcast. Three, (13010, 13110, 13210), correspond to re-broadcast of the work with normal playback rate (slope=1.0); three, (13020, 13120, 13220), correspond to re-broadcast of the work with time-scale compression by a factor of 2 (slope=2.0); and three, (13005, 13105, 13205), correspond to re-broadcast of the work with time-scale expansion by a factor of 2 (slope=½). As further shown in FIG. 13, at each re-broadcast interval, three (3) stream broadcasts are initiated (compressed, normal, expanded) and that these offset data streams intercept one another at regular intervals where the lines cross (lines intersect when the playback locations and playback times are equal). Clients wishing to view or listen to a work at a different rate can make a seamless transition to the new rate at points of intersection because the playback locations at the intersections are identical in each of the streams. As still further shown in FIG. 13, transition leader 13001 (normal playback rate, slope=1) is shown to demonstrate a transition from playback stream 13005 (one-half normal playback rate, slope=½) to playback stream 13020 (twice normal playback rate, slope=2.0). Additionally, a time-scale modified transition leader 13002 (twice normal playback rate, slope=2.0) is used to transition from playback stream 13105 (one-half normal playback rate, slope=½) to playback stream 13110 (normal playback rate, slope=1) at a time before the normal intersection with playback stream 13220. Embodiment 5000 can be used to generate the re-broadcasts and the time-scale modified leaders to enable the client to traverse the re-broadcast matrix shown in FIG. 13. In that case, client requests will be received by Request Processor 5500 and transmitted in the manner described above with respect to the description of embodiment 5000.

[0131] For purposes of clarity and ease of understanding the present invention, the foregoing detailed description has used constant time-scale modification factors, but the present invention is not thusly limited and includes the use of varying time-scale modification factors using the same method and apparatus described above. Thus, Time-Scale Modification may be varied with time without loss of generality. In this case, the duration and slope of such a continually varying Time-Scale Modified signal can be computed using any one of a number of formulae, including the following formula:

[0132] Duration=previous duration+(time-interval * tsm_factor)  (11)

[0133] Although for clarity and ease of understanding the previous inventions have been described broadcasting a single work, it should be clear that embodiments of the present invention are not thusly limited and the inventive technique can be applied to multiple works existing in a single embodiment.

[0134] Another aspect of the present invention relates to the use of extra information broadcast in conjunction with an audio or audio-visual work from a server to restrict, or direct, playback rates at the client. Embodiments of this aspect of the present invention can be used in a variety of ways. For example, a public service announcement regarding emergency information, safety information, and the like may be missed if the client is listening at a very fast rate (learning impaired and hearing impaired individuals may wish to have important public service or emergency broadcasts played at playback rates below the normal playback rate to aid in comprehension). Since these messages may be of vital importance, a need exists to restrict the playback rate for the client in a client-server system that supports Time-Scale Modification, or to notify the client of the importance of these messages.

[0135] In accordance with this aspect of the present invention, information used to restrict, or direct, playback rates at the client may be “in-band” (i.e., occurring within the signal being transmitted, for example, as a specific frequency tone or data code within a header of a data packet) or “out-of-band” (i.e., occurring within a data packet associated with, but not comprising, media data).

[0136] FIG. 14 shows a block diagram of embodiment 21000 of the present invention which transmits information relating to the content and/or appropriate playback speed of media data to clients receiving the media data.

[0137] As shown in FIG. 14, Streaming Data Source 21100 provides, as output: (a) data representing an audio or audio-visual work through Network 21200 (Network 21200 is a network in the broadest sense described above), there are many methods which are well known to those of ordinary skill in the art for fabricating Streaming Data Source 21100, and (b) a signal to TSM Control Source 21150 indicating the transmission of the data and client identifier information for clients who will have playback rates restricted. Note that the components of embodiment 21000 may exist in separate locations connected to one another via a network or any other communication means (where the use of the term means is used in the broadest sense possible).

[0138] As further shown in FIG. 14, in response to the signal, TSM Control Source 21150 transmits playback code data, for example, a code, on Network 21200 to all identified clients that will have their playback rates directed for data received from Streaming Data Source 21100.

[0139] Although FIG. 14 shows the transmission of the media data and the playback code data being transmitted over the same network, the present invention is not thusly limited. In fact, the present invention includes embodiments where the media data and playback codes are transmitted over different communications paths. Further, the transmission of the playback code need not be coordinated with the transmission of the media data as described above. The playback code data can be transmitted prior to the transmission of the media data and include information used to enable its coordination with the media data. For example, the playback code data may include times (and time intervals) in the media work that are targeted for use in restricting playback rates.

[0140] As still further shown in FIG. 14, Capture Buffer 21400 receives the following, as input: (a) media data input from Network 21200; (b) requests for information about the amount of data stored therein from a Capture Buffer Monitor (not shown, this is optional); and (c) requests for media stream data from TSM System 21800. In response, Capture Buffer 21400 produces the following, as output: (a) a stream of data representing portions of an audio or audio-visual work (applied as input to TSM System 21800); (b) a stream of location information used to identify the position in the stream of data (applied as input to TSM System 21800); and (c) an indication of the amount of data stored therein (applied as input to the optional Capture Buffer Monitor). It should be well known to those of ordinary skill in the art that Capture Buffer 21400 may include a digital storage device. There are many methods well known to those of ordinary skill in the art for utilizing digital storage devices such as, for example, a “hard disk drive,” to store and retrieve general purpose data and there exist many commercially available apparatus which are well known to those of ordinary skill in the art for use as a digital storage device such as, for example, a CD-ROM, a digital tape, a magnetic disk, and so forth. TSM Control Decoder 21450 receives, as input, playback code data from Network 21200 (as discussed above, it can receive this data from a different communication channel as well). TSM Control Decoder 21450 produces, as output, playback code data and applies it, as input, to TSM Rate Determiner 21700.

[0141] As yet still further shown in FIG. 14, TSM Rate Determiner 21700 receives the following, as input: (a) a signal (from TSM Control Decoder 21450) that represents a playback rate; (b) client generated playback rate requests (received by a client interaction interface apparatus in accordance with any one of many methods which are well known to those of ordinary skill in the art (not shown for ease of understanding the present invention)); (c) a parameter designated Interval_Size; and (d) a parameter designated Speed_Change_Resolution. In response, TSM Rate Determiner 21700 produces, as output a rate signal representing a TSM rate, or playback rate, which rate signal is applied as input to TSM System 21800. TSM Rate Determiner 21700 generally passes client generated rate requests to its output (without modification), thereby enabling the client to control the playback rate. Whenever TSM Rate Determiner 21700 receives information from TSM Control Decoder 21450, TSM Rate Determiner 21700 processes that information to determine an appropriate playback rate to output. For example, TSM Rate Determiner 21700 may override the client requested rate request if the information from TSM Control Decoder 21450 specifies that the media work being received is of critical importance to public safety. Additionally, TSM Rate Determiner 21700 may process the information from TSM Control Decoder 21450 according to a rule-set or other algorithm specified by the client. For example, the rule-set or algorithm can fast-forward through all commercial content in the media work being received, slow down for specific types of content, using techniques described in U.S. Patent Application entitled “Method and Apparatus for Generation of Listener Interest Filtered works, which patent application has the same inventor as the present application and is incorporated by reference herein.

[0142] In a preferred embodiment of the present invention, TSM Rate Determiner 21700 uses a parameter Interval_Size to segment the input digital data stream in Capture Buffer 21400 and to determine a single TSM rate for each segment of the input digital stream. Note, the length of each segment is given by the value of the Interval_Size parameter. Further, TSM Rate Determiner 21700 uses a parameter Speed_Change_Resolution to determine appropriate TSM rates to pass to TSM System 21800. A desired TSM rate is converted to one of the quantized levels in a manner which is well known to those of ordinary skill in the art. This means that the TSM rate, or playback rate, can change only if the desired TSM rate changes by an amount that exceeds the difference between quantized levels, i.e., Speed_Change_Resolution. As a practical matter then, parameter Speed_Change_Resolution filters small changes in TSM rate, or playback rate. The parameters Interval_Size and Speed_Change_Resolution can be set as predetermined parameters for embodiment 21000 in accordance with methods which are well known to those of ordinary skill in the art or they can be entered and/or varied by receiving user input through a user interface in accordance with methods which are well known to those of ordinary skill in the art. However, the manner in which these parameters are set and/or varied are not shown for ease of understanding the present invention.

[0143] Embodiments of TSM System 21800 and Playback System 21500 have been described in detail above.

[0144] Although FIG. 14 shows embodiment 21000 to be comprised of separate modules, in a preferred embodiment, the modules are embodied as software programs or modules which run on a general purpose computer such as, for example, a personal computer. It should be well known to one of ordinary skill in the art, in light of the detailed description above, how to implement these programs or modules in software.

[0145] Conversely, components of embodiment 21000 may exist in separate locations connected to one another via a network or any other communication means (where the use of the term means is used in the broadest sense possible).

[0146] Advantageously, in accordance with the present invention, the above-described information used to control the playback speed during particular portions of the media work, for example, commercials. Thus, a client may be prevented from fast forwarding through the commercials. However, in an alternative embodiment, clients may pay for the ability to automatically fast-forward through all commercial advertisements in an audio or audio-visual work being received. In such an alternative embodiment, a user interface module (fabricated in accordance with any one of the many methods which are well known to those ordinary skill in the art) receives client requests and charge information to effectuate the functionality.

[0147] FIG. 15 shows a block diagram of embodiment 22000 of the present invention in which information relating to the playback speed and/or content of the media data being broadcast to clients is embedded in the media work. As shown in FIG. 15, Media Work Source 22100 provides, as output, data representing an audio or audio-visual work to Compositer 22160 transmits playback code data, for example, a code, to Compositer 22160. Compositer 22160 outputs a data signal which is encoded by Encoder 22170 using any number of methods well known to those of ordinary skill in the art and transmitted to Network 22200 Network 22200 is a network in the broadest sense described above) to clients, for example, who have requested the audio or audio visual work.

[0148] As further shown in FIG. 15, data from Network 22200 is applied as input to Decoder 22310 which decodes the encoded data signal using any number of methods well known to those of ordinary skill in the art. The decoded data is applied as input to Separator 22320 which separates the playback code data from the media data and applies the playback code data as input to TSM Control Decoder 22450 and the media data as input to TSM System 22800. TSM Control Decoder 22450 decodes the playback code information and produces as output a TSM Rate which is applied as input to TSM Rate Determiner 22700. In accordance with the present invention, TSM Rate Determiner 22700, TSM System 22800 and Playback System 22500 are the same as the corresponding components described above with respect to embodiment 21000. In accordance with this embodiment of the present invention, TSM Rate Determiner 22700 uses the TSM Rate from TSM Control Decoder to set the playback rate and override client input.

[0149] Although FIG. 15 shows embodiment 22000 to be comprised of separate modules, in a preferred embodiment, the modules are embodied as software programs or modules which run on a general purpose computer such as, for example, a personal computer. It should be well known to one of ordinary skill in the art, in light of the detailed description above, how to implement these programs or modules in software.

[0150] Conversely, components of embodiment 22000 may exist in separate locations connected to one another via a network or any other communication means (where the use of the term means is used in the broadest sense possible).

[0151] Although the detailed description used the terms playback rate and TSM rate, and the terms playback and playback apparatus, these terms should be understood to include any type of presentation rate (i.e., a rate of presentation of information) and any type of presentation apparatus. As such, these terms are to be understood as being used in the broadest sense. In addition, although the detailed description used the terms media, media work, media data, media broadcast, audio or audio-visual work, and information, these terms should be understood to refer to any type of information or data. As such, these terms are to be understood as being used in the broadest sense