Multiplex communications – Special services – Special feature of multiplex telephone terminal
Reexamination Certificate
1997-12-01
2002-06-04
Jung, Min (Department: 2663)
Multiplex communications
Special services
Special feature of multiplex telephone terminal
C348S014060
Reexamination Certificate
active
06400693
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communications apparatus for multimedia information such as an AV (Audio Visual) communications apparatus used for a television telephone apparatus, and video-conference systems.
2. Related Background Art
In recent years, along with the inauguration of the communications services through ISDN circuits, a particular attention has been given to the television telephone, video-conference systems, and other AV services which use a digital circuit of the kind.
Along the inauguration of AV services, the service regulations for AV services, protocol regulations, structural regulations of multiplexing frames for multimedia, encoding methods for animated image information, and the like are recommended as recommendations H.320, H.242, H.221, H.230, H.261 among others.
Now, with reference to the accompanying drawings, the recommendation H.221 will be described.
FIG. 1
is a view which shows the frame structure regulated by the JTU-TS Recommendation H.221 for 64 kbps one channel.
FIGS. 2A and 2B
are views which represent the bit assignments between FAS one multiframe=eight submultiframes (one subframe=two frames).
In accordance with the Recommendation H.221, frame structures are regulated in the AV services on the 64 kbps to 1,920 kbps channels. The frame structure regulated by the Recommendation H.221 for the 64 kbps one channel is a structure constituted by 80 octet per frame. As shown in
FIG. 1
, numerals 1 to 8 on the axis of abscissa represent bit numbers, and numerals 1 to 80 on the axis of ordinate represent octet numbers. As shown in FIG.
1
and
FIG. 2A
, the FAS represents the frame synchronization signals. By these signals, the frame synchronization and multiframe synchronization are controlled. Also, the monitoring function of communications quality, the notification of warning information, and the like are controlled by the signals.
On the other hand, the BAS shown in
FIG. 2B
represents the bit rate assignment signals. By these signals, the terminal capability, the bit rate assignment designation per media in the actual frame, and various other controls and notifications are performed. As shown in
FIGS. 2A and 2B
, the BAS is transferred to the even-numbered frames, while the corresponding error correction bits are transferred to the odd-numbered frames.
The Recommendation H.242 regulates procedures such as the capability information exchanging sequence and the mode switching sequence using the inchannel BAS between AV terminals.
The Recommendation H.320 regulates the systems aspect all over the AV services.
The Recommendation H.230 regulates the transfer frame synchronization or various controls and notifications which require emergency responses as additional information regarding the functions required for the performance of AV services.
The Recommendation H.261 regulates the encoding and decoding methods for animated information at a speed of p×64 kbps (p=1 to 30).
Now, with reference to the accompanying drawings, the description will be made of the circuit which performs the videocodec function in accordance with the Recommendation H.261 conceding the encoding and decoding of animated image information.
FIG. 3
is a block diagram which shows the circuit structure for performing the videocodec function according to the Recommendation H.261 conceding the encoding and decoding of animated image information.
The inputted video signals are provided with a common intermediate image format called CIF/QCIF which is regulated as a compromise plan between the NTSC and PAL methods which are the television methods of Japan, U.S.A., and European nations.
The inputted video signals are supplied to a information source encoder
201
. The information source encoder
201
selects the INTRA mode, INTER mode, or MC mode per unit of macro block, executes DCT (Diffuse Cosine Transformation) of inputted image/estimated errors per block of each pixel (8×8), and quantizes coefficients. Here, in the estimated processing, a two-dimensional spatial filter may be used per block of pixels (8×8).
The output from the information source encoder
201
is supplied to a video signal multiplexing encoder
202
. The video signal multiplexing encoder
202
performs variable encoding in accordance with the four-layered structure of a frame, a group of blocks (GOB), a macro block (MB), and a block. The output from the video signal multiplexing encoder
202
is supplied to a transmission buffer
203
. The transmission buffer
203
controls encoding on the basis of the transmission rate.
The output from the transmission buffer
203
is supplied to a transmission encoder
204
. The transmission encoder
204
performs transmission encoding by use of the frames for BCH (
511
and
492
) error correction encoding.
On the other hand, a transmission decoder
209
on the decoding side performs the operations contrary to the encoding described above by means of a reception buffer, video signal multiplexing decoder
207
, and information decoder
206
, thus decoding the received image signals to the CIF/QCIF video signals.
Now, with reference to the accompanying drawings, the description will be made of the fundamental sequence to execute multimedia communications on images, voices, data (all the user information other than the images and voices) and the like in accordance with the recommendations described above.
FIG. 4
is a flowchart which shows the fundamental sequence regarding the execution of the multimedia communications on images, voices, data (all the user information other than the images and voices) and the like in accordance with the ITU-TS Recommendations.
At first, when a communications apparatus for multimedia information (hereinafter referred to as an apparatus on the transmission side) is actuated, the outchannel call control is actuated following this actuation so that a reception is notified to an apparatus on the reception side. If this operation is for the ISDN circuit, a call setup sequence is actuated by a Dch.
In the apparatus on the transmission side, step S
1
is executed at first as shown in FIG.
4
. In the step S
1
, whether or not the reception is a television telephone call is determined. In a case of the ISDN circuit, it is determined whether the call is a telephone call, television telephone call, or a call which differs from them completely by use of the BC (transmission capability) information element, HLC (high level layer matching capability) information element, LLC (low level layer matching capability) information element, and other information elements.
When the call is ascertained to be a television telephone call, step S
2
is executed. In the step S
2
, the Dch call is set up to establish a first connection.
Then, step S
3
is executed. In the step S
3
, a frame synchronization is set up by the FAS retrieval and detection, the sending out of A bit=0 and detection in the setup connection (corresponding to the Bch, Hch, or the like in the ISDN). After the synchronized setup, step S
4
is executed. In the step S
4
, the capability of an apparatus on the reception side is determined by the capability information exchanging sequence by the capability BAS transmission and reception detections.
Then, step S
5
is executed. In the step S
5
, a multimedia multiplexing assignment is determined in the first connection, thus executing the BAS command transmission, and the mode switching over sequence by the reception. In this way, the multimedia multiplexing communication is started. Actually, in this case, the sequences are often those executing only the voice reception when the setup of additional connections is executed continuously. For example, the communication is started in accordance with the voice 56 kbps in a mode where the H.261 image is off as shown in FIG.
4
.
After the commencement of the communications, step S
6
is executed. In the step S
6
, it is determined whether or not there is a capability of additional connection setup in
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