Speech coding selection based on call related information

[0002] 1. Field of the Invention

[0003] The present invention relates to voice messaging systems. More particularly, it relates to voice messaging systems wherein the speech coding used to code incoming voice messages is changeable based on incoming call related information.

[0004] 2. Description of Related Art

[0005] Voice messaging has become an everyday requirement in today's society. Early voice messaging apparatus comprised magnetic cassette tapes which recorded a significant amount of voice messages, e.g., 60 minutes of voice messages. However, cassette tapes were disadvantageous because of the mechanics and time required to fast-forward and rewind the cassette tapes to the storage points of individual messages.

[0006] More recently, particularly as the size of memory has increased in density while at the same time decreased in price, digital voice messaging systems have become commonplace. Digital voice messaging systems store incoming voice messages in digital memory, reducing the mechanics and cost, and increasing the reliability over conventional analog voice messaging systems.

[0007] It is commonly known to encode voice messages for storage in digital voice messaging systems to maximize the length of voice messages which may be stored in a finite amount of memory. Various conventional voice compression techniques exist, many having various effective data rates. For instance, linear predictive coding (LPC), code-excited linear predictive (CELP) coding, RPE-LTP, or adaptive differential pulse code modulation (ADPCM) are examples of techniques, any one of which may be utilized by conventional digital voice messaging systems, and any one of which may be implemented at varying effective data rates. These coding techniques result in a compression of the data yielding a reduction in the data rate necessary to represent the underlying voice message. The effective data rate resulting from a general linear approach to digitizing toll quality speech (e.g., 8 KHz, 8-bit sampling, i.e., 64 Kb/s) with respect to an effective data rate resulting from a coding technique such as CELP, LPC, or ADPCM forms a compression ratio of the coding. These compression techniques have been developed for use with digital voice messaging systems which in general reduce the number of bits necessary to represent voice message data. Although it is recognized that the compression techniques are improved over time to better approach toll quality speech, in general the greater the compression ratio, the greater the degradation in the quality of the speech stored in voice memory. “Compression ratio” as used herein refers to the ratio of the number of bits representing the voice message in linear form divided by the number of bits used to represent the same voice message in compressed or coded form.

[0008] FIG. 6 shows a prior art voice messaging apparatus such as a digital telephone answering device (TAD) 11. Although described with respect to embodiments relating to a TAD, the present invention is equally applicable to a voice mail type system and voice messaging systems in general.

[0009] In FIG. 6, a signal from a microphone or other analog signal source 106 is input to a codec, analog-to-digital converter, or other digitizing device in a voice recorder/playback module 20 for conversion to m-law or A-law pulse code modulated (PCM) data. The m-law or A-law PCM data is encoded and compressed by a variable compression ratio encoding routine in the processor 18. For playback, a variable compression ratio decoding routing in the processor 18 together with a codec, digital-to-analog converter, or similar device in the voice recorder/playback module 20 converts voice message data retrieved from voice memory into an analog signal for output to speaker 108.

[0010] While control of the TAD 11 and handling of voice processing is shown in FIG. 6 as being handled in processor 18, a separate digital signal processor may be utilized to handle the compression and other voice processing tasks. The processor 18 controls the encoding and decoding tasks performing the compression and decompression of the voice message data. Processor 18 also controls storage of the compressed (encoded) speech data into voice memory 100, and controls the retrieval of compressed speech data from the voice memory 100.

[0011] The TAD 11 further includes an alpha-numeric keypad 36 and display 27 as are known in the art. The display 27 displays call related information regarding an incoming call, e.g., a caller's telephone number and household name, received from a central office 13 via a telephone line interface 48 and call related information detector/receiver 12.

[0012] However, conventional voice messaging systems are limited by the compression rate used and the amount of available message memory. Messages which are received after the memory becomes full, such as after a long vacation, are conventionally refused.

[0013] Thus, there is a need to maximize the available message memory for use beyond that which is conventionally available such that more messages may be stored.

[0014] In accordance with the principles of the present invention, a variable voice compression ratio device in a voice messaging device comprises a processor, a call related information detector/receiver, and a call related information/coding database to associate pre-set call related information with one of a plurality of voice compression ratios. The processor compares incoming call related information to the pre-set call related information to determine the desired voice compression ratio for storage of a voice message corresponding to the incoming call.

[0015] In another aspect of the invention, a variable voice compression ratio device comprises a memory containing a plurality of voice compression ratio values each associated with respective call related information. A call related information receiver receives incoming call related information, and a processor compares the received call related information with the respective call related information contained in the memory to identify one of the plurality of voice compression ratio values.

[0016] A method of setting an effective data rate for storage of a voice message for an incoming call in accordance with the present invention provides detection and reception of call related information relating to the incoming call. The detected and received call related information is compared with a memory containing pre-set call related information associated with respective effective data rates. An effective data rate is then set for storage of the voice message of the incoming call based on the comparison.

[0017] Features and advantages of the present invention will become apparent to those skilled in the art from the following description with reference to the drawings, in which:

[0018] FIG. 1 is a block diagram of a telephone answering device (TAD) in accordance with the principles of the present invention.

[0019] FIG. 2A shows the contents of an exemplary embodiment of the call related information/coding database in FIG. 1.

[0020] FIG. 2B shows the contents of another exemplary embodiment of the call related information/coding database in FIG. 1.

[0021] FIG. 3A shows a flow chart of selecting a desired coding technique/effective data rate for each of a plurality of priority parties.

[0022] FIG. 3B shows a flow chart invoking one of a plurality of coding techniques/effective data rates in accordance with an embodiment of the present invention.

[0023] FIG. 4 is a front view of a TAD in accordance with the principles of the present invention.

[0024] FIG. 5 is a more detailed block diagram of the TAD shown in FIG. 1.

[0025] FIG. 6 shows a conventional TAD.

[0026] The present invention relates to a voice messaging system such as a telephone answering device or voice mail system which utilizes differing coding processes and/or data rates resulting in varying compression ratios based on a database relating call related information of the incoming call to particular ones of the differing coding processes and/or data rates. Thus, the coding technique and compression ratio are adjusted based on call related information associated with an incoming call received by the voice messaging system.

[0027] The disclosed embodiments relate to a digital telephone answering device (TAD) in particular, but the principles disclosed herein are equally applicable to voice mailbox type systems and voice messaging systems in general. Moreover, while the disclosed embodiments describe the reception of Caller ID information as an example of call related information, the invention relates to the reception and processing of any call related information.

[0028] Many telephone companies offer a special service which transmits call related information to a called party before the call is answered. One such service is commonly referred to as caller identity deliver, or “Caller ID”. Using Caller ID, typically a caller's telephone number and/or household name is transmitted by the telephone company to the called party generally during the silent interval between the first two rings. More sophisticated systems transmit call related information while a party is off-hook, e.g., Caller ID/Call Waiting (CIDCW). Caller ID systems which receive caller ID information from incoming calls are known.

[0029] FIG. 1 shows a TAD 11 including reception of call related information, e.g., Caller ID, in accordance with the principles of the present invention. The present invention utilizes the Caller ID information to determine a pre-set coding technique and effective data rate corresponding to a particular compression ratio to be utilized to encode the subsequent voice message.

[0030] In FIG. 1, the TAD 11 includes a call information detector and receiver 12 which decodes call related information (e.g., Caller ID information) regarding the calling party. Current Caller ID services provide the telephone number and/or household name of a calling party before the calling party is answered. The call related information is transmitted by the central office 13 over a telephone line 14 and is received by the call related information detector/receiver 12 generally during the silent interval between the first and second ring (or before the first ring in other countries, e.g., in the United Kingdom). The call related information is stored in a conventional call related information directory 117 by processor 18. The processor 18 may be any suitable microprocessor, microcontroller, or digital signal processor (DSP), or even a combination of multiple processors such as a microcontroller and a DSP.

[0031] The TAD 11 also includes a suitable voice recorder/playback module 120 connected to a standard microphone 106 and a standard speaker 108. The voice recorder/playback module 120 handles the outgoing pre-recorded greeting message in conjunction with the processor 18, as well as the playback of voice messages.

[0032] The TAD 11 further includes a dual tone, multiple frequency (DTMF) decoder and a DTMF generator within processor 18 for controlling the voice recorder/playback module 120. Thus, the contents of the call related information/coding table or database 16 and other features of the TAD 11 may be programmed remotely using DTMF tones which are decoded into control signals by the processor 18.

[0033] The TAD 11 inventively further includes a call related information/coding table or database 16 either in random access memory (RAM) or in re-writable read only memory (ROM) such as electrically erasable programmable read only memory (EEPROM) or flash memory. The call related information/coding database 16 contains manually entered information relating call related information to a voice storage quality parameter corresponding to various coding techniques and/or effective data rates corresponding to a variety of available compression ratios. The call related information is entered using keypad 36 and display 27. The voice storage quality parameters may be any number or other reference to a particular coding technique or effective data rate to be invoked for compression and storage of the incoming voice message.

[0034] As an example, five voice storage quality parameters may be defined, e.g., 1 (lowest quality) to 5 (highest quality). Of course, more or less variation in the possible choices of encoding techniques and/or effective data rates will respectively provide more or fewer possible choices for the user to select from. Moreover, more or fewer numbers of voice storage quality parameters may be utilized, depending upon the particular application.

[0035] The various voice storage quality parameters may correspond to one coding technique, e.g., CELP, but to various frame lengths corresponding to various effective data rates, or it may correspond to multiple types of coding techniques having differing effective data rates, or a mix of both. For example, three CELP voice storage quality parameters may be provided corresponding to a 10 millisecond (mS) frame duration, 20 mS frame duration, and 25 mS frame duration CELP coding process, respectively. The voice storage parameter may alternatively or additionally refer to pre- and post-processing techniques such as interpolation or decimation. The particular coding technique, and frame duration or other information relating to effective data rate, are invoked in the processor 18 based on a selected or default voice storage quality parameter. The voice message is stored in voice message memory 100 after processing by the invoked coding technique and/or effective data rate. If a codebook is employed, a different number of indices may be used to achieve various compression rates. Moreover, different levels of LPC parameters and/or quantization, etc. may be used to achieve various compression rates.

[0036] Voice message memory 100 may be any suitable re-writable memory such as random access memory (RAM), electrically erasable programmable read only memory (EEPROM), or flash memory. Non-volatile memory such as flash memory or EEPROM are preferred to prevent loss of stored messages in the event of power failure to the TAD 11.

[0037] Each of the voice messages are stored in the voice memory 100 together with conventional header information. Additionally, the header stored with each voice message includes the type of coding process/effective data rate used to encode the voice message. Optionally, the header information may include the voice storage quality parameter which is mapped into a particular coding process/effective data rate in a table accessed by the processor 18.

[0038] Upon decoding, the processor 18 invokes the complementary decoding and decompression routines corresponding to the coding technique and effective data rate used to encode the voice message, as determined by the content of the header information stored with the particular voice message.

[0039] Any portion or all of the incoming call related information may be used either as an entry in the call related information/coding database 16 or for use in comparison of the incoming call related information. For instance, information which may be utilized for comparison and/or entry in the call related information/coding database 16 includes the area code of the incoming telephone, the last name of the household, the full telephone number, and/or the full household name.

[0040] FIG. 2A shows the contents of an exemplary embodiment of the call related information/coding table or database 16 shown in FIG. 1. In FIG. 2A, call related information entries 302 are related to selected voice storage parameters (i.e., storage quality) 304, and mapped to effective data rates 306 of coding techniques operable by processor 18. The exemplary call related information/coding table or database 16 includes five manually entered records 308-316.

[0041] The first record 308 indicates that if “JOHN DOE” calls, as determined by a comparison of household name of incoming call related information to the first record 308, then processor 18 is to invoke the coding process and effective data rate corresponding to a desired compression ratio in the processor 18 as corresponding to a voice quality storage parameter of “3”.

[0042] The second record 310 indicates that the processor 18 is to invoke the same coding process and effective data rate as with respect to the first record 308, if a voice message is received from the telephone number “880-555-2000”.

[0043] The second and third records 312, 314 indicate that the highest quality coding process having the highest effective data rate corresponding to the lowest compression ratio provided by the TAD 11 is to be invoked by the processor 18 if “MOM SMITH” or “GRANDMA SMITH” call.

[0044] All other incoming calls to the TAD 11, including those without call related information sent from the central office 13, are to utilize the default setting for encoding the voice message, which in record 316 is set to the lowest quality, i.e., highest compression ratio corresponding to a voice storage quality parameter of “1”.

[0045] FIG. 2B shows the contents of another exemplary embodiment of the call related information/coding table or database in FIG. 1. The call related information/coding table or database 16 is similar to that shown in FIG. 2A, but maps a particular coding process in column 354 to the call related information entries 350 and voice storage quality parameter entries 352 of individual records 356-364. FIGS. 2A and 2B demonstrate that any aspect of the particular coding process representing a differing effective data rate may be used to correlate a desired priority level (i.e., voice storage quality parameter), to the possible voice coding and compression capabilities of the TAD 11.

[0046] FIG. 3A shows a flow chart for manually inputting call related information regarding desired priority parties into the call related information/coding table or database 16 of the TAD 11, and for initially selecting the desired voice storage quality parameters for those callers from among those available in the TAD 11. Alternatively, or in addition, the call related information may be input in conjunction with another feature or function of the TAD 11. For instance, the call related information may be gleaned from speed dial information input into the TAD 11 together with a prompt to the user as to the coding level and/or quality of the stored voice messages received from that particular caller.

[0047] In particular, the first step of the process shown in FIG. 3A prompts a user on the display 27 (FIG. 1) to enter via the keypad 36 (FIG. 1) call related information identifying a first party for which to preset a voice storage quality parameter. The process then prompts the user to select the desired voice storage quality parameter for that first entered priority party, e.g., either “1”, “2”, “3”, “4”, or “5”. While the present embodiment is described with respect to five coding techniques and/or effective data rates, it is to be understood by those of skill in the art that virtually any number of levels of voice storage quality may be possible. For example, only two selections may be made available, e.g., “high” and “low”. Alternatively, the frame duration may be made adjustable in the coding technique to allow selection of 1 to 99 mS frame durations corresponding to a storage quality selection of “1” to “99”.

[0048] In step 206, the entry process prompts the user for the entry of any additional priority parties. If the user desires to enter additional entries in the call related information/coding table or database 16, then the process returns to step 202 for entry of call related information of the next priority party. If, on the other hand, there are currently no additional priority parties to enter in the call related information/coding database 16, then the process 200 shown in FIG. 3A ends.

[0049] Entries in the call related information/coding table or database 16 may be amended and/or appended to by the user at any time. For instance, additional entries may be appended to the end of the table or database contained in the call related information/coding table or database 16. Moreover, previously entered records in the call related information/coding table or database 16 may be overwritten as desired.

[0050] FIG. 3B shows a flow chart of the inventive operation of the TAD 11, i.e., a comparison and invoking of a designated coding process and effective data rate performed by processor 18.

[0051] In particular, the first step 252 of the process 250 shown in FIG. 3B receives call related information from an incoming call. The received call related information is compared in step 254 with records in the call related information/coding table or database 16 (FIG. 1). If a match is determined in step 256 as between any portion of the received incoming call related information and an entry in the call related information portion of the call related information/coding table or database 16, then a preset coding process and effective data rate is invoked for voice processing of the received voice message in step 258. If there is no match, then the default coding process and effective data rate is invoked in step 260.

[0052] The default coding process and effective data rate is shown as an additional record in the call related information/coding database 16, but may alternatively be a manual switch setting on the TAD 11.

[0053] In step 262, the incoming voice message is encoded by the designated coding process at the designated effective data rate, and stored in voice message memory 100. After storage of the voice message, the TAD 11 returns to an idle state to await another call, playback of stored voice messages, etc.

[0054] The principles of the present invention may be invoked upon the occurrence of a predetermined event, e.g., upon the voice message memory 100 becoming near full, e.g., 90% full. In this event, the processor can then compress each subsequent message based on the associated call related information. Alternatively, to free up some space in the voice message memory 100, the processor may initially store all messages at a default compression rate. Then, as the memory becomes full, review and recompress all stored messages based on associated call related information and the desired or default compression rate set in the call related information/coding table or database 16.

[0055] Moreover, the call related information/coding table database 16 can be expanded to include a plurality of compression levels to associate with the various call related information. In this case, the various levels could be associated with, e.g., various levels of usage of the voice message memory. Thus, as the voice message memory fills, higher compression ratios can be used for the various messages based on the information contained in the call related information/coding table or database 16. This feature would help preserve as many voice messages as possible as the memory fills up.

[0056] The display 27 (FIG. 1) displays call related information about an incoming call, as well as the designated (or default) voice storage quality parameter or other information associated with that incoming call, as shown in FIG. 4.

[0057] In more detail, FIG. 4 shows the TAD 11 packaged to fit within a console 26. The console 26 may be equipped with a standard handset 30 and a standard modular telephone jack 32, e.g., an RJ-11 connector. A control panel 28 includes a liquid crystal display (LCD) forming display 27, and the alpha-numeric keypad 36. As noted above, the display 27 shows the call related information, i.e., the incoming telephone number and/or the household name associated with the incoming telephone number. The display 27 is also used during entry of the records in the call related information/coding table or database 16 for prompts to the user, and for showing entered information. The TAD 11 otherwise includes conventional features such as a control button 100 for recording or playback of an outgoing greeting message, playback and record manual controls 102, and call related information log scrolling controls 104 for scrolling a display of the conventional call related information contained in the call related information directory 117.

[0058] FIG. 5 shows a detailed circuit diagram of a TAD 11 provided in accordance with the principles of the present invention. The TAD 11 includes a control circuit 44, memory block 46 and a telephone line interface (TLI) circuit 48. Control circuit 44 includes processor 18 which controls the system by executing instructions that are stored in memory 46. Memory block 46 includes programmable read-only memory (ROM) 52 for storing program code. The call related information/coding table or directory 16 is stored in flash memory in memory block 46. Random access memory (RAM) 54 is also provided for general use and to store log data for call related information, voice message data, and the like.

[0059] The telephone line interface circuit 48 includes circuitry which permits the TAD 11 to be connected directly to a standard modular telephone jack 32, e.g., an RJ-11 connector. The telephone line interface circuit 48 also includes various control and monitoring circuits that are common to ordinary customer premises equipment. These circuits may include circuitry to interface the telephone handset 30, a ring detect interface circuit 58 provides a signal indicative of a ring signal of the incoming calls to the processor 18, and an on/off hook detect circuit 70. In the illustrated embodiment, the telephone line interface circuit 48 also includes an isolated filter and demodulating circuit 60 to demodulate an incoming serial data stream. A universal asynchronous receiver/transmitter (UART) 62 is used to convert the demodulated serial data received from the filter and demodulating circuit 60 to a parallel format read by the processor 18 via address and data busses 64. Alternatively, the processor 18 can perform the UART function.

[0060] In the illustrated embodiment, data received by the filter and demodulating circuit 60 includes call related information, e.g., Caller ID data representing the telephone number of the incoming call. Data corresponding to the household name associated with the incoming call may also be received by the filter and demodulating circuit 60. The protocol and other features relating to the otherwise conventional features of the circuit shown in FIG. 3 are known, e.g., as described in U.S. Pat. No. 4,582,956, the disclosure of which is hereby incorporated by reference into the present specification.

[0061] Frequency shift keying, phase shift keying, amplitude modulations, quadrature amplitude modulation or any other suitable modulation technique may be used for transmitting the incoming serial data stream containing the call related information to the TAD 11.

[0062] A real time clock circuit 65 and a system timing circuit 66 may also be provided to provide timing for the TAD 11. The real time clock circuit 65 provides the system with the current time and date for time and date stamping received voice messages, while the system timing circuit 66 is used for instruction cycle timing of the processor 18.

[0063] In the illustrated embodiment, when a caller initiates a call to the TAD 11, its call related information is transmitted by the central office 13 and received by the telephone number detector/receiver 12 (FIG. 1), e.g., during the silent period between the first and second rings. If the received call related information does not match any call related information pre-programmed in the call related information/coding table or database 16, then the TAD 11 invokes the default coding technique and effective data rate for voice processing of a voice message from that caller.

[0064] Voice signals are transmitted to and from the telephone line through the RJ11 connector 32 and pass through the telephone line interface circuit 48 to the voice recorder/playback circuit 120. The subsequent incoming voice message signal is digitized and compressed by the selected coding technique and/or effective data rate for efficient storage by the processor 18. The incoming voice messages are linked with call related information received with respect to that incoming call, and may be retrieved by the user through the voice recorder/playback circuit 120.

[0065] The processor 18 also controls the functioning of the voice/playback circuit 20 through controls such as PLAY, RECORD, FAST FORWARD, REWIND, ERASE and STOP signals (FIG. 2).

[0066] A TAD in accordance with the principles of the present invention may also operate in a remote message playback and DTMF detection mode. In this mode, the user listens to a pre-recorded announcing message at a remote telephone. The incoming call from the user is answered by the TAD as described above. At any time during the outgoing announcing message, the user may key-in predefined user ID information using a DTMF keypad generating DTMF tones indicating that the user wishes to listen to stored voice messages. The voice recorder/playback circuit 120 detects the presence of the DTMF tones and converts them into control information for the processor 18. The DTMF tones form a control signal which the processor 18 responds to by either playing back a recorded voice message or by deleting a recorded voice message. As noted above, DTMF tones may also be used to program the information in the call related information/coding table or database 16 remotely.

[0067] Although an embodiment of a voice messaging system in accordance with the principles of the present invention has been described as a stand-alone device, the voice messaging system may be in the form of a circuit card which is installed within a larger device such as a personal computer (PC) or private branch exchange (PBX).

[0068] It can be appreciated that the equipment and method of the invention improves upon the traditional voice messaging system by enabling the call itself to automatically select and invoke the coding technique and/or effective data rate corresponding to a data compression for recording of the voice message.

[0069] Voice messaging systems in accordance with the principles of the present invention prevent waste of voice memory on undesirable memory, provide relatively more voice memory to calls from chosen sources, and store voice messages from important calls at a higher voice quality than other, less important voice messages.

[0070] While the invention has been described with reference to the exemplary preferred embodiments thereof, those skilled in the art will be able to make various modifications to the described embodiments of the invention without departing form the true spirit and scope of the invention.