US 5,847,752 AGrant
Method for Call Setup and Control of Videotelephone Communication
Issue Date:1998-12-08
•7 Claims
•5 Drawing Sheets
Abstract
A method and arrangement for connection setup and control of digitally compressed audio, video and data signals between videotelephones of the analog and digital communication networks (for example, telephone network, mobile telecommunication) and a method and arrangement for the transmission of still pictures and/or between videotelephones of the same category are disclosed. In videotelephony, a bidirectional full-duplex information exchange is fundamentally assumed in both directions, that is, both communicating videotelephone terminal equipment are usually transmitter and receiver of audio, video, control and, potentially, other information types at the same time. The method for connection setup between videotelephone communication terminal equipment in a transmission network using a protected transmission protocol in a framework of ITU-T V.8 initialization and of an ITU-T V.34 modem, has the steps of: supporting videotelephone communication within the framework of the ITU-T V.8 initialization in that at least a request for high transmission quality for videotelephone communication is signaled to the network during connection setup between a calling terminal equipment and a called terminal equipment; and recognizing in the calling terminal equipment a type of the called terminal equipment and a type of the transmission network connected thereto.
Metadata
Assignee
- Siemens Aktiengesellschaft
Inventor
- Istvan Sebestyen
Application Information
Application Number:US 7763409
Filing Date:1997-01-24
Priority Date:1994-07-25
Art Unit:273
Classifications
IPC:
H04N 712H04M 1100
Field of Search:
34837914-1993.01;93.05-93.08;93.14;93.17;93.26;93.28-93.32;93.34
Patent Drawings (5 sheets)
Description
Background of the Invention
The invention is directed to a method for call setup and a method for controlling digitally compressed audio, video and data signals between videotelephone terminal equipment via analog and/or digital communication networks, as well as a method for optional transmission of still pictures, datafiles, camera as well as cursor remote control information between videotelephone terminal equipment.
Videotelephone connectible via analog interfaces to an analog or to a digital communication network are used for the simultaneous transmission of digitally encoded audio, video and data signals. An analog network in this sense is, for example, the analog telephone network, which shall also be referred to as PSTN (Public Switched Telephone Network) below. The digital mobile radiotelephone network GSM (Global Standard for Mobile Communications) can be cited as an example of a digital communication network. After a call setup between two videotelephone terminal equipment, the acoustic source signals are converted into analog electrical oscillations by a microphone of the transmitting apparatus, these being digitally encoded, compressed and transmitted to the receiving videotelephone terminal equipment via the analog telephone network isochronically with the video information. In the receiving videotelephone terminal equipment, the received, digitally compressed voice signals are decompressed and converted into analog electrical signals that are isochronically converted into acoustic signals and output. At the same time, the analog motion pictures of the transmitting apparatus registered by a camera are likewise digitally encoded, compressed and transmitted to the receiving videotelephone terminal equipment via the analog telephone network isochronically with the audio information. In the receiving videotelephone terminal equipment, the received, digitally compressed video signals are decompressed and converted into analog electrical signals that are isochronically output in the receiving videotelephone terminal equipment as moving pictures. A bidirectional, full-duplex information exchange in both directions is fundamentally assumed in videotelephony, i.e. both communicating videotelephone terminal equipment can be transmitter and receiver of audio, video, control and, potentially, other types of information at the same time.
In particular, still pictures and computer datafiles can be simultaneously transmitted from the transmitting to the receiving videotelephone terminal equipment as additional options. Still picture transmission is assigned a special role in case the line quality of the network only allows a low overall transmission rate (for example, below 8 kbit/s) that no longer assures the required minimum quality of moving pictures.
Summary of the Invention
An object of the invention is to offer a method and an arrangement for reliable, simply realized communication between videotelephone terminal equipment regardless of whether the communication terminal equipment are connected to the respective communication network via analog or digital interfaces.
In general terms the present invention is a method for connection setup between videotelephone communication terminal equipment using a protected transmission protocol in the framework of the ITU-T V.8 initialization and of an ITU-T V.34 modem. The videotelephone communication is supported within the framework of the ITU-T V.8 initialization in that, among other things, the request for a high transmission quality for the videotelephone communication is still signalled to the network during the connection setup. The calling terminal equipment recognizes the type of the called terminal equipment and the type of the transmission network connected thereto.
The present invention is also a method for the control of videotelephone communication between videotelephone communication terminal equipment in a virtual control channel within the framework of an ITU-T V.34 information transfer. A virtual control channel with HDLC LAP protected transmission of the control data blocks in bidirectional full-duplex mode with the control instructions is set forth in the following Table:
Advantageous developments of the present invention are as follows.
For controlling different information types, a "virtual" channel is allocated to each of the information types using the HDLC LAP method and either fixed or freely definable transmission priorities and/or error correction priorities are allocated to the various data types. Preset normal parameters are employed at the beginning of the communication instead of freely definable priorities. This normal parameters are capable of being redefined during the course of the communication using the control instructions EMPFPAR and SENDPAR.
Image datafiles are embedded in ITU-T T.84/ISO/IEC 10918-3 datafile formats. The parameters of the image datafiles are embedded in the ITU-T T.84/ISO/IEC 10918-3. Continuous color images according to ITU-T T.81/ISO/IEC 10918-1 ("JPEG") with variable image size with sequential or progressive image construction are supported. "Icons" of the continuous color images according to ITU-T T.81/ISO/IEC 10918-1 ("JPEG") with variable image size are supported. Bilevel (for example, black/white) images according to ITU-T T.82/ISO/IEC ii544 ("JBIG") with variable image size with sequential or progressive image construction are supported. Preparations for transmission are negotiated and set with the control instructions GEREIG, EMPFAR and SENDPAR. The control of the still picture transmission ensues with the control instructions SENDSTD and ABRSTD, and their reception is acknowledged with ACKNOW or negatively acknowledged with NOTACK in case of error.
Arbitrary program or data datafiles are defined according to ITU-T T.434. Preparation for transmission are negotiated and set with the control instructions GEREIG, EMPFAR and SENDPAR. The control of the datafile transmission ensues with the control instructions SENDDAT and ABRDAT, and their reception is acknowledged with ACKNOW or is negatively acknowledged with NOTACK in case of error.
With a remote control of a camera preparation for transmission are negotiated and set with the control instructions GEREIG, EMPFAR and SENDPAR. The control of the datafile transmission ensues with the control instructions CAMSTR, and their reception is acknowledged with ACKNOW or is negatively acknowledged with NOTACK in case of error.
Remote control of a cursor ensues with the control instructions CURSSTR, and their reception is acknowledged with ACKNOW or is negatively acknowledged with NOTACK in case of error. Preparation for transmission is negotiated and set with the control instructions GEREIG, EMPFAR and SENDPAR.
These components of the present invention contain:
call setup
control of the communication
transmission of still picture
transmission of datafiles (file transfer)
optional transmission of the camera remote control command
optional transmission of the cursor (pointer) remote control command.
A bidirectional, full-duplex information exchange in both directions is fundamentally assumed given employment of the inventive method.
Dependent on the individual forms of realization and special characteristics, the invention is based on the following information technology and/or communication technology standards:
The norming of voice encoders with very low bit rates current in the ITU-T, for example for videotelephony in the public switched telephone network, leads to qualitatively good voice encoders (approximately the quality of CCITT G.726 Recommendation) with transmission rate of 4-8 kbit/s.
The norming of moving picture encoders current in the ITU-T and ISO/IEC with very low bit rates, for example for videotelephony in the public switched telephone network (Draft ITU-T H.26P), leads to qualitatively usable moving picture encoders with the expedient transmission rate of 8-24 kbit/s.
The norming of still pictures with continuous gray scale values or colors concluded in the ITU-T and ISO/IEC (ITU-T T.81/ISO/IEC 10918-1) with very low bit rates, for example for videotelephony in the public switched telephone network with the expedient transmission rate of 4-24 kbit/s.
The norming of two-color still pictures concluded in the ITU-T and ISO/IEC (ITU-T T.82 I ISO/IEC 11544) with very low bit rate, for example for videotelephony in the public switched telephone network with the expedient transmission rate of 2-24 kbit/s.
The ongoing standardization in the ITU-T and ISO/IEC of the datafile exchange format ITU-T T.84/ISO/IEC 10918-3 ("Extensions") for video communication. The still picture compression algorithms ITU-T T.81/ISO/IEC 10918-1 ("JPEG"--for continuous color images) and ITU-T T.82/ISO/IEC 11544 ("JBIG"--for bi-level still pictures) are supported.
The current norming in the ITU-T of multiplexing of audio-visual data types with very low bit rate, for example for videotelephony in the public switched telephone network with transmission rate of 9.6-32 kbit/s.
The norming of the high-speed modem ITU-T V.34 passed in the ITU-T that enables the transmission rate of 2.4-28.8 kbit/s in the public switched telephone network dependent on the line quality.
The norming of the modem initialization standard ITU-T V.8 passed in the ITU-T that offers the basis of an initialization procedure that is also suitable for videotelephony if it is expanded with functionalities and code points for videotelephony.
The norming of the datafile description passed in the ITU-T in the ITU-T T.434 "Binary file transfer for the telematic services".
The advantages of inventive methods are described below:
In the call setup:
The PSTN videotelephones currently offered in the marketplace make use of slower modems--belonging in the family of the ITU-T V.32. These modems only allow transmission speeds that permit a lower quality of audio and video pictures as well as for still and moving pictures. An advantage of the ITU-T V.32 modem solution is the possibility of initially beginning the communication between two videotelephone terminal equipment as normal voice telephone communication--as desired by the videotelephone service--and adding the video communication as needed. This, however, is not directly possible given employment of the high-speed modem ITU-T V.34 that enables a significantly better audio and video quality. An inventive method also enables the above-desired functionality given employment of the ITU-T V.34 modem and of the ITU-T V.8 initialization pertaining thereto.
In the control of the communication:
The current standardization of the multiplexing of data types (audio, video, data and control information) provides the independent transmission of virtual channels within a LAP-x method (Link Access Protocol) method to be developed. A separate, protected virtual channel with high transmission priority should thereby be allocated to control information types. This is achieved with a version of the already known HDLC-LAP method. An inventive method should enable the control of the videotelephone communication.
In the transmission of still pictures:
The videotelephones currently available in the marketplace only offer the transmission of still pictures in the simplest form. A "frozen" moving picture is either offered with its physical dimension or with doubled resolution. An inventive method should enable the definition and control of the optional still pictures significantly more versatilely in videotelephone communication. Still pictures of different natures (for example, black/white and color pictures) and flexible image resolution size and still pictures with sequential image construction (line-by-line or block-by-block) and/or with progressive image construction (an image with coarser image quality is transmitted first, but fast; the image quality is improved step-by-step as the transmission continues). Miniature images (so-called icons) are likewise supported. Despite low data rates, progressive image construction--a particular advantage of the inventive method--allows complicated still pictures to be encoded, transmitted and decoded with minimum delay in real time, whereby the image quality of the decoded image improves step-by-step up to the maximum image quality.
In the transmission of datafiles:
An inventive method optionally enables a datafile exchange between transmitting and receiving videotelephone terminal equipment (file transfer with the assistance of ITU-T T.434).
In the transmission of camera remote control instructions:
An inventive method describes an optional remote control of the camera of the communicating partner. This serves for the support of certain applications such as, for example, traffic monitoring.
In the transmission of cursor remote control instructions:
An inventive method describes an optional remote control of a cursor (pointer) on the picture screen of the communicating partner. This serves for the support of visual communication.
Brief Description of the Drawings
The features of the present invention which are believed to be novel, are set forth with particularity in the appended claims. The invention, together with further objects and advantages, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in the several Figures of which like reference numerals identify like elements, and in which:
FIG. 1 is a block diagram of a videotelephone communication terminal equipment KES;
FIG. 2 depicts the application of the CI signal and the exchange of the CM/CL menu in the framework of the ITU-T V.8 initialization procedure;
FIG. 3 is the table 3/V.8 of the "Call Function" category of an exemplary embodiment of the expanded ITU-T V.8 initialization procedure;
FIG. 4 is the table 4/V.8 of the "Modulations Modi" category of the expanded ITU-T V.8 initialization procedure;
FIG. 5 is the table 5/V.8 of the encoding of the protocol category of the expanded ITU-T V.8 initialization procedure.
Description of the Preferred Embodiments
Preferably, the following elements of information technology and/or telecommunications that have been standardized or are to be standardized in future are employed:
Modem ITU-T V.34 with a higher transmission rate (up to 28000-32000 bits/s) and the initialization procedure according to ITU-T V.8 belonging thereto.
An expansion of the ITU-T V.8 Recommendation needed for the recited applications.
The reliable and error-resistant transmission of information blocks (an HDLC-LAP-conforming packet-switched transmission protocol) of the draft "ITU-T H.24P".
The current standardization of voice encoders with very low bit rate for videotelephony in the public switched telephone network in ITU-T with a transmission rate of 5-7 kbit/s.
The standardization of moving picture encoders current in the ITU-T and ISO/IEC with very low bit rates, for example for videotelephony in the public switched telephone network in ITU-T (draft ITU-T H.26P) with the expedient transmission rate of 8-24 kbit/s.
The norming of the datafile description concluded in the ITU-T in the ITU-T T.434 "Binary file transfer for the telematic services".
The norming of still pictures with continuous gray scale values or colors concluded in the ITU-T and ISO/IEC (ITU-T T.81/ISO/IEC 10918-1) with low bit rates with the expedient transmission rate of 4-24 kbit/s.
The norming of two-color still pictures concluded in the ITU-T and ISO/IEC (ITU-T T.82/ISO/IEC 11544) with low bit rates with the expedient transmission rate of 2-24 kbit/s.
The ongoing standardization in the ITU-T and ISO/IEC of the datafile exchange format ITU-T T.84/ISO/IEC 10918-3 ("Extensions") for video communication. The still picture compression algorithms ITU-T T.81/ISO/IEC 10918-1 ("JPEG"--for continuous color images) and ITU-T T.82/ISO/IEC 11544 ("JBIG"--for bi-level still pictures) are supported.
The afore-mentioned standards need to be combined and partially expanded for realizing the present invention.
Some properties of communication terminal equipment to be provided for the realization of an inventive method are explained in greater detail below:
A typical videotelephone terminal equipment for the inventive call setup satisfies at least the features of a telephone for the public switched telephone network or of a radiotelephone and, additionally, a communication control means for controlling the data transmission with the assistance of an HDLC-LAP-conforming transmission protocol (in order to assure an error-free communication), an ITU-T V.34 modem, and a suitable ITU-T V.8 initialization protocol. Additionally, at least the transmitting communication terminal equipment (KES) should also contain an audio and a video encoding means for the compression of the audio and video input digital signal or, respectively, the receiving communication terminal equipment (KEE) and also at least an audio and video decoding means for the decompression of the received audio and video information data. FIG. 1 depicts a simplified block circuit diagram of such a videotelephone communication terminal equipment. During the connection, the videotelephone is connected either to another videotelephone or to a normal telephone.
The connection to other videotelephones or to normal telephones is either produced as connection of the videotelephones (the expansions necessary for this are yet to be standardized in the ITU-T V.8) or, if this is not possible, to normal telephones. What this means for the call setup is that the transmitting videotelephone initially attempts--immediately, i.e. without time delay--to address the called apparatus as receiving "videotelephone" (signalling with the assistance of ITU-T V.8). This is important because, according to ITU-T V.8, the network must be immediately signalled that an especially high-quality communication channel must be made available for the connection under certain circumstances (for example, given transmission by satellites) since the highest possible ITU-T V.34 rate should be supported. A V.8 signalling in the same connection after the end of a normal telephone call (for example, a switching into the videotelephone mode) with the assistance of ITU-T V.8 and ITU-T V.34 is therefore neither meaningful nor possible. When the called terminal equipment answers as "videotelephone" (likewise with the assistance of ITU-T V.8), the digital connection for the information exchange can be set up with the assistance of ITU-T V.34. If the called apparatus is, for example, a data modem or a fax device, then the connection is aborted. When the called apparatus is a normal telephone that has no ITU-T V.8 procedure available to it, then the switching to the normal "telephone mode" ensues automatically. In this case, the connection is continued as a normal "telephone call".
When, however, two videotelephones encounter one another, then the terminal equipment identifications are exchanged between transmitter and receiver according to ITU-T V.8 in order to signal that videotelephone communication is possible.
The ITU-T V.34 procedure of the modem is initiated after successful ITU-T V.8 signalling. The selection of the highest mode rate is also implemented according to rules of ITU-T V.34 after the "line probing" and "training" in the full-duplex mode (i.e. determining the line quality and testing the maximally suitable modem rate).
For the full-duplex mode, the control commands of the communication controller must be exchanged as part of the ITU-T-V.34 data transfer. To that end, a virtual "supervisory control" channel (control channel) must be defined. The data packets of this channel are specifically identified as control packets. The following are included among the control commands valid for both communication partners:
Mutual exchange of the device properties (GEREIG) of the transmitter and receiver (for example, identification of the video parameters (for example, picture screen resolution, options for still picture, datafile transfer, camera remote control, remote cursor movement capability, etc.)). Exchange of the device properties ensues once, namely at the beginning of the connection.
Communicating the preferred reception parameters (EMPFPAR) (optional--at any time)
Setting the transmission parameters (SENDPAR) (on the basis of the declared device properties of the transmitter and receiver and taking the preferences of the other party into consideration)--setting and exchange at least once, at the beginning of communication, then as often as desired at any arbitrary point in time. The setting is respectively defined by the transmitting party; the receiver can merely express his "reception wishes" (preferential wishes). When no receiver preferences are received, the transmitter sets the values that derive on the basis of the common device parameters.
Sending a still picture (SENDSTD) (optional--at any time)
Fetching a still picture (ABRSTD) (optional--at any time)
Sending a data datafile (SENDDAT) (optional--at any time)
Fetching a data datafile (ABRDAT) (optional--at any time)
Camera remote control of the partner (CAMSTR) (optional--at any time)
Cursor remote control (CURSSTR) (optional--at any time)
Normal termination of the communication (EXIT)
Abort of the communication (ABBRUCH)
Acknowledgment of the control commands (ACKNOW)
The actual communication between transmitter and receiver corresponds to the data phase of ITU-T V.34 (after successful "ITU-T V.34 Resynch"). Here, communication is carried out with the previously declared, maximum rate. An error correction mode according to HDLC LAP is required for videotelephone communication. To that end, the digitized data blocks must be generated and numbered (HDLC LAP according to Draft ITU-T H.24P). A transmission priority is assigned to each information type. Control data thereby have the highest priority and have this given full error correction. When a block was recognized as faulty, then it must either be retransmitted (if the information type must be transmitted unconditionally protected, for example in the "Supervisory Channel", still picture transmission file transfer) or the faulty block can also be ignored (for example, moving picture transmission). A detailed description of the information block types and of the appertaining priorities is set forth in Table 1.
The fixed priority means that the priority cannot be changed during the course of the communication. The default priority is that priority value that was set by the system as initial value at the start of the communication. In the definable priority, the transmitter can modify these values once or repeatedly either on demand by the receiver or based on the transmitter's own decision (control command SENDPAR). The receiver's wish is announced with the communication of the preferred reception parameters (control command EMPFPAR, optional command that can be output by the receiver at any time). As reaction, the transmitter can (but need not) modify the transmission and error correction priorities. For example, the receiver can prefer a fast, error-free audio signal transmission to delayed voice-image synchronization. The transmitter can likewise modify the transmission priorities on its own initiative, for example the transmission priority of the still picture in a connection at the expense of the moving picture priority.
The correct reception of the control parameters SENDPAR and EMPFPAR is acknowledged with the control command (ACKNOW) or negatively acknowledged (NOTACK) given an error.
As a specific example: The solution of the desired audio communication (as in the case of a normal telephone) at the start of the communication and the "switching" into videotelephone communication is carried out in the following way: call setup V.8 initialization, V.34 modem initialization. After successful execution, V.34 data mode, exchange of device properties (optional preferences), both parties only send audio information to the other party at the start. In the "switching" to videotelephone mode, at least one of the communication parties begins to also embed moving picture information into the transmission data stream.
Inventive methods enable the definition and control of the optional still picture transmission. Still pictures of different types (for example, black/white and color pictures) and flexible image resolution size, and still pictures with sequential image construction (line-by-line or block-by-block from top to bottom and from left to right) and/or progressive image construction (first, an image with coarser image quality is transmitted, but fast; the image quality is improved step-by-step as the transmission continues). Miniature images (so-called icons) are likewise supported.
The optional reception possibilities of the transmitter and receiver are set after exchange of the device properties (with the control command GEREIG) of the transmitter and of the receiver. This exchange only ensues once, at the start of the connection or upon RESET given error and abort. The communication of the preferred reception parameters (with EMPFPAR) can also optionally ensue. This exchange is optional and can ensue at any time.
Setting the transmission parameters ensues with SENDPAR on the basis of the declared device properties of the transmitter and receiver and the preferences of the other party. This setting and exchange ensues at least once, at the start of the communication, as reply to the device properties and preferences (if present), can potentially ensue again an arbitrary number of times at any arbitrary point in time. The setting is respectively defined by the transmitting party; the receiver can merely express his "reception wishes" (preferential wishes). If no reception preferences are received, the transmitter sets the values that derive on the basis of the common device parameters. A determination is made in GEREIG as to whether and what kind of still picture can be supported by the receiving terminal equipment (for example, image size, possibility of sequential and of progressive image construction, support of ITU-T T.81/ISO/IEC 10918-1 ("JPEG") and/or ITU-T T.82/ISO/IEC 11544 ("JBIG"). The transmission of a still picture is optionally initiated at any time with the command (SENDSTD) or ABRDAT (fetch a still picture offered by the other party). Subsequently, standard image data blocks are mixed with the other data types and transmitted--with the specified or default priority. Alternatively, the fetching of a still picture from the other party is likewise optionally possible at any time (with the control instruction ABRSTD). In the transmission, the image data are embedded in a data stream that was specified according to ITU-T T.84/ISO/IEC 10918-3. All datafiles defined in this way contain all important information with respect to the image to be transmitted (for example, image resolution, image dimension, type of image construction, etc.). The type of display of the received image lies at the discretion of the receiver. The successful execution is acknowledged with the acknowledge instruction (with the command ACKNOW) or a negative acknowledgment (NOTACK) is communicated (for example, when the image cannot be decoded).
Given the control command "transmission of datafiles" (file transfer), the exchange of device properties, preferences and settings of the parameters ensues as described above in the transmission of still pictures. Only the commands for the transmission of a datafile (SENDDAT) deviate therefrom. This command is optional and can be output at any time. The successful execution is acknowledged with the acknowledge instruction, the and ACKNOW. Otherwise, a negative acknowledgment (NOTACK) is communicated, for example when the image cannot be decoded.
Subsequently, datafiles shaped according to ITU-T T.434 in specifically identified data blocks are mixed into the data stream of the videotelephone data blocks.
The fetching of a datafile is achieved with the control instruction (command) (ABRDAT). This instruction is likewise optional and can be output at any time. The successful execution is acknowledged with the acknowledge instruction (ACKNOW) or a negative acknowledgment (NOTACK) is communicated.
Subsequently, datafiles shaped according to ITU-T T.434 in specifically identified data blocks are mixed into the data stream of the videotelephone data blocks.
A cursor remote control (CURSSTR) can also be optionally output at any time by the transmitting party. The successful execution is acknowledged with the acknowledge instruction (ACKNOW) or a negative acknowledgment (NOTACK) is communicated.
The instruction "Normal Termination" of the communication (EXIT) leads to the proper termination of the communication. The devices are placed into their basic condition. This instruction must be acknowledged with an acknowledgment instruction (ACKNOWL) of the other party. The end of the communication can only be ended then.
An instruction "Abort the Communication" (ABBRUCH) can, if provided, lead to the fast abort of the communication. This instructions is usually output after an error in order to achieve a proper termination of the terminal equipment and to abort the communication. It is beneficial but not absolutely necessary that this instruction be answered with the acknowledgment instruction (ACKNOWL). The instruction "Abort with RESET" has a similar function, but with the difference that the communication is not aborted, rather all parameters are reset to their initial stage in order to enable a renewed communication.
Further, an exemplary embodiment is proposed for the ITU-T V.8 and ITU-T V.34 parameterization upon insertion of expansions. The V.8bis initialization procedure is similar.
FIG. 2 illustrates the V.8 "Start up" procedure of the session initialization. This is absolutely necessary in the context of a V.34 modem. The V.8 "Start up" procedure is active once, at the start of the communication connection.
As can be seen from FIG. 2, the delay after connection through-connect amounts to about 1 second at the side of the calling terminal equipment (DCE) in a connection according to V.8 (and, subsequently, V.34). Thereafter, the CI signals (CI=call identifier) are transmitted with 300 b/s until the called terminal equipment (DCE) does not reply with an ANSam signal ("Answer tone signal" of V.8). Subsequently, the calling DCE sends the signals Cms ("Call Menu" signals with the selection of what are referred to as the "call Function" categories--for example, "Voice Memory Telephone", with the selection of the modem modulation--for example, for V.34 full-duplex, with the selection of the protocol category--LAP "?"). With its "JM" signals, the called DCE reflects the same type of information in order to declare its device properties. A determination is made on the basis of the two tables as to whether communication is possible between the two parties. If yes, then the V.34 procedure usually follows within 2 seconds.
When the called DCE is not a "Voice Memory Telephone" but, for example, a normal telephone, then the V.8 procedure is aborted with the expiration of a specific time span (timer). This time span is not specified in the V.8 but in the application of the "Voice Memory Telephone".
The CM/JM code allocations of the "Voice Memory Telephone" are lacking in the current version of ITU-T V.8. (See FIG. 3.) These allocations are undertaken by the ITU on demand. An example of how they could be undertaken is recited below.
The Table 3/V.8 specifies the "Call Function" category of V.8. The ITU has already reserved some code points in the first octet. Two code points should be reserved for the "Voice Memory Telephone". The illustrated code points were occupied by way of example. The modulations modi are specified in the Table 4/V.8 (see FIG. 4).
The octet for possible "protocols" can also be left out in case only one protocol is specified for the "Voice Memory Telephone" service. If a plurality of protocols are to be employed, for example for different network types (PSTN, mobile), then this octet is used and corresponding code points are specified for the protocol types.
The GSTN access category is defined in Table 6/V.8 (not shown). It indicates whether the calling or the called terminal equipment is connected via the mobile radiotelephone network.
The exchange of additional information is not provided by ITU-T V.8 since V.8 is too slow (300 b/s) for the exchange of larger information. All additional negotiations or, respectively, control commands should therefore run via the procedures of the ITU-T V.34 modem.
A V.34 "start-up" also sequences after the successful execution of the V.8 "start-up". This comprises:
V.34 "Line Probing" (estimate of line quality)
V.34 HDX (half-duplex) or FDX (full-duplex) "training"
V.34 parameter exchange
V.34 resynchronization.
Only after this does V.34 change to its data transfer mode where the actual user data are exchanged.
What is referred to as a "retrain" (retraining) of V.34 is executed if the line quality during the data communication is in fact inadequate. The data transfer is interrupted and a new transmission rate with adequate quality is set by "retrain". The transmission of the data is then continued. No isochronic transmission of the user data (for example, audio information) can ensue during the "retrain" in the current version of V.34.
The ITU-T V.34 procedure of the modem is initiated after successful ITU-T V.8 signalling. The selection of the highest modem rate is also implemented according to rules of ITU-T V.34 after the "line probing" and "training" in full of half duplex mode (i.e. determination of the line quality and testing the maximally suitable modem rate). Subsequently, the V.34 parameters are exchanged again according to ITU-T V.34 (only for the half-duplex mode) and the control commands needed for the communication are exchanged with 1200 bit/s. The control commands must be exchanged for the full-duplex mode. The control commands must be exchanged as part of the data transfer for the full-duplex mode. To that end, a virtual "supervisory control" channel must be defined. The data packets of this channel are specifically identified. At least the following are valid as control commands:
Exchange of additional device properties of the transmitter and receiver such as, for example, identifier of the audio/voice compression, mailbox capability, half/full-duplex capability, communication of the receiver preferences;
Setting the common, preferred transmission or reception parameters on the basis of the declared device properties of the transmitter and receiver; opening and shooting sic! virtual user channel (for example, for audio).
Sending a message;
Fetching a message;
Addressing a voice mailbox;
Normal termination of the communication;
Abort of the communication.
The invention is not limited to the particular details of the method depicted and other modifications and applications are contemplated. Certain other changes may be made in the above described method without departing from the true spirit and scope of the invention herein involved. It is intended, therefore, that the subject matter in the above depiction shall be interpreted as illustrative and not in a limiting sense.
Claims
What is claimed is:
1. A method for connection setup between videotelephone communication terminal equipment in a transmission network using a protected transmission protocol in a framework of ITU-T V.8 initialization and of an ITU-T V.34 modem, comprising the steps of: supporting videotelephone communication within the framework of the ITU-T V.8 initialization in that at least a request for high transmission quality for videotelephone communication is signalled to the network during connection setup between a calling terminal equipment and a called terminal equipment; and recognizing in the calling terminal equipment a type of the called terminal equipment and a type of the transmission network connected thereto.
2. A method for control of videotelephone communication between videotelephone communication terminal equipment in a virtual control channel within a framework of an ITU-T V.34 information transfer, comprising the steps of: providing a virtual control channel with HDLC LAP protected transmission of control data blocks in bidirectional full-duplex mode; providing control instructions for effecting videotelephone communication between the videotelephone communication terminal equipment, the control instructions being set forth in the following Table: Control Number Control instruction Function Action time of actions reactions __________________________________________________________________________ GEREIG Exchange of device Immediately after Once ACKNOW (prescribed) properties; GEREIG is setup of the virtual or NOTACK simultaneously sent by control channel with both parties potentially following SENDPAR EMPFPAR Parameters of the desired After exchange of Arbitrary ACKNOW (optional) reception preferences. the GEREIG or Can be independently NOTACK requested by one or both parties. SENDPAR Setting the transmission Immediately after At least ACKNOW (prescribed) parameters on the basis reception and once or of received GEREIG and acknow-ledge of NOTACK EMPFPAR GEREIS of the other party SENDSTD Send still picture. Image Any time if the Arbitrary ACKNOW (optional) datafile and image para- option is permitted or meters embedded in ITU- at the receiver NOTACK T T.84 / ISO/IEC 10918-3 (GEREIS) data stream ABRSTD Fetch still picture. Image Any time if the Arbitrary ACKNOW (optional) datafile and image para- option is permitted or meters embedded in ITU- at the transmitter NOTACK T T.84 / ISO/IEC 10918-3 and receiver data stream SENDDAT Send datafile. Datafile Any time if the Arbitrary ACKNOW (optional) and datafile parameters option is permitted or embedded in ITU-T T.434 at the receiver NOTACK data stream (GEREIS) ABRDAT Fetch datafile. Datafile Any time if the Arbitrary ACKNOW (optional) and datafile parameters option is permitted or embedded in ITU-T T.434 at the transmitter NOTACK data stream and receiver CAMSTR Remote control (pan, Any time if the Arbitrary ACKNOW (optional) zoom, etc.) of the camera option is available at NOTACK of the other party the transmitter and permitted at the receiver (GEREIS, EMPFPAR) CURSSTR Cursor remote control. Any time if the Arbitrary ACKNOW (optional) Moving a cursor in the option is available at or image surface of the the transmitter and NOTACK other party permitted at the receiver (GEREIS, EMPFPAR) EXIT Proper termination of the Can be initiated Once ACKNOW (prescribed) communication from both sides or NOTACK ABORT Abort in case of error -- Can be initiated Once ACKNOW (prescribed) end of the communication from both sides or NOTACK __________________________________________________________________________ Control Number Control instruction Function Action point in time of actions reactions __________________________________________________________________________ ABORT Abort in case of error -- Can be initiated Arbitrary ACKNOW with RESET maintain the from both sides or NOTACK (prescribed) communication, reset all with default parameters subsequent GEREIG ACKNOW Positive acknowledgment Control receiver Once None (prescribed) of a control instruction NOTACK Negative Control receiver Arbitrary New control (prescribed) acknowledgment of a instruction control instruction __________________________________________________________________________
3. The method according to claim 2, wherein, for controlling different information types, a virtual channel is allocated to each of the information types using an HDLC LAP method, and wherein one of fixed or freely definable transmission priorities and/or error correction priorities are allocated to various data types, whereby preset normal parameters are employed at a beginning of communication instead of freely definable priorities, said normal parameters being redefinable during the communication using the control instructions EMPFPAR and SENDPAR.
4. The method according to claim 2, wherein image datafiles are embedded in ITU-T T.84/ISO/IEC 10918-3 datafile formats; wherein parameters of the image datafiles are embedded in the ITU-T T.84/ISO/IEC 10918-3; wherein continuous color images according to ITU-T T.81/ISO/IEC 10918-1 with variable image size with sequential or progressive image construction are supported; wherein continuous color images according to ITU-T T.81/ISO/IEC 10918-1 with variable image size are supported; wherein bi-level images according to ITU-T T.82/ISO/IEC ii544 with variable image size with sequential or progressive image construction are supported; wherein preparations for transmission are negotiated and set with the control instructions GEREIG, EMPFAR and SENDPAR; and wherein control of still picture transmission ensues with the control instructions SENDSTD and ABRSTD, and reception of the control instructions SENDSTD and ABRSTD is acknowledged with control instruction ACKNOW or negatively acknowledged with control instruction NOTACK in case of error.
5. The method according to claim 2, wherein arbitrary program or data datafiles are defined according to ITU-T T.434; wherein preparation for transmission of arbitrary program or data files are negotiated and set with the control instructions GEREIG, EMPFAR and SENDPAR; control of datafile transmission ensues with the control instructions SENDDAT and ABRDAT, and reception of the control instructions SENDAT and ABRSDAT is acknowledged with control instructions ACKNOW or is negatively acknowledged with control instructions NOTACK in case of error.
6. The method according to claim 2, wherein regarding remote control of a camera preparations for transmission are negotiated and set with the control instructions GEREIG, EMPFAR and SENDPAR; control of datafile transmission ensues with the control instruction CAMSTR, and wherein reception of the control instruction CAMSTR is acknowledged with control instruction ACKNOW or is negatively acknowledged with control instruction NOTACK in case of error.
7. The method according to claim 2, wherein remote control of a cursor ensues with the control instruction CURSSTR, and wherein reception of the control instruction CURSSTR is acknowledged with control instruction ACKNOW or is negatively acknowledged with control instruction NOTACK in case of error, and wherein preparation for transmission is negotiated and set with the control instructions GEREIG, EMPFAR and SENDPAR.
Patent Citations (2)
| Patent | Date | Inventor | Cited By |
|---|---|---|---|
| EPX535890A2 | 1993-07-01 | ||
| WOXWO93/18607 | 1993-09-01 |
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