JP2580955B2 - Data multiplexing device and separating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data multiplexing device and a demultiplexing device, and more particularly, to an ATM (Asynchronous Transfer Mode).
de) The present invention relates to a multiplexing apparatus and a separating apparatus for audio / video code data in a multimedia system corresponding to a communication system.

[0002]

2. Description of the Related Art FIG. 4 shows a schematic configuration of a conventional apparatus for multiplexing audio / video coded data in a multimedia system. In the figure, an input video signal is input to a video encoding unit 1.
Is converted into digital data, and further subjected to data compression processing as required, and is led out to the buffer memory 4.

At this time, the video coding unit 1 codes the input video signal in accordance with the coding control signal VCNT output from the video coding control unit 5 based on the transmission buffer occupation amount BOC from the buffer memory 4. You.

[0004] The encoded video data is input to the buffer memory 4, temporarily stored, and then read according to a read request signal VRCNT from the multiplexing unit 9.

On the other hand, in the audio encoding unit 2, the input audio signal is digitized and encoded, and the read request signal AR output from the multiplexing unit 9 is output like the encoded video data.
Output according to CNT.

In the multiplexing unit 9, the read request signal VRCN
Based on T and ARCNT, video and audio coded data are multiplexed in a fixed time slot (TV, TA: see FIG. 5) within a fixed cycle T.

However, since the amount of generated information of video coded data changes with time, the number of time slots allocated to video coded data must be changed to the TV time in FIG. Buffer memory 4 in
Must be set to the maximum amount of information output from.

As a result, when the amount of generated information of video coded data between TV sets is small and does not reach the assigned time slot, dummy data is inserted by the multiplexing unit 9 as shown in FIG. It has become.

In such a conventional data multiplexing method, it is necessary to insert dummy data as shown in FIG.
When data is to be transmitted in a fixed length cell format as in the M network, dummy data must be transmitted as cells as shown in FIG. Therefore, although the dummy data cell portion can be used for transmitting other data, it cannot be used, and transmission efficiency is deteriorated.

Each cell-coded video encoded data is naturally delayed by the operation of the buffer memory 4, but the information of how long the delay is is not generated at all in the configuration of FIG. Since the output is not output, the receiving side cannot execute control to make the propagation delay time including the buffer memory of the encoded video data constant.

[0011] Therefore, while the propagation delay of the encoded audio data is constant, the delay of the encoded video data cannot be made constant. As a result, synchronization (lip sync) between the video and audio is lost. There is a disadvantage that it cannot be maintained constant.

In particular, when the video encoding method is CBR (Consta
nt Bit Rate) format, there is a one-to-one correspondence between the buffer memory occupancy and the delay time.
Based on this, buffer memory control is performed to keep the propagation delay time of the video encoded data constant, so that synchronization (lip sync) between audio and video can be synchronized.

However, VBR (Variable Bit Rat)
e) When video encoded data of the format is used, the correspondence between the occupation amount of the buffer memory and the delay time is not established, and the propagation delay time of the video encoded data can be kept constant. Therefore, as described above, there is a problem that synchronization between audio and video cannot be constantly adjusted.

An object of the present invention is to provide a data multiplexing apparatus which efficiently multiplexes audio data and video data and is suitable for multimedia communication corresponding to an ATM communication system, and a demultiplexer thereof.

Another object of the present invention is to provide a data multiplexing apparatus and a demultiplexing apparatus capable of maintaining constant synchronization of both data on the receiving side when audio data and video data are cellized and multiplexed. To provide.

[0016]

According to the present invention, there is provided a data multiplexing apparatus comprising: video coding means for coding a video signal; a buffer memory for temporarily storing the video coded output; and data stored in the buffer memory. Read control means for reading video data of a fixed length, delay detection means for detecting a delay time in which the read video data is delayed by passing through the buffer memory, and buffer information for the detected delay time A means for multiplexing the read data from the memory, a video cell forming means for adding additional information such as a header and a trailer to each of the multiplexed output video data to form a cell, and deriving an audio signal. Audio encoding means for converting the audio encoded output into cells by adding additional information such as a header and a trailer to each of the fixed-length audio data and deriving the cells. Characterized in that it comprises a voice cell means, and a cell multiplexing means for transmitting by multiplexing and this such as video cell and the audio cell.

In the data separation apparatus according to the present invention, the cell multiplexing means has means for detecting that the audio cell and the video cell have occurred at the same time to generate a coincidence detection signal; The means includes means for detecting that the amount of stored data has become zero and generating a zero detection signal, and wherein the video celling means has a time slot period addition time for inserting the additional information for celling. Means for generating an information insertion signal, wherein the read control means reads data from the buffer memory when at least one of the simultaneous detection signal, the zero detection signal, and the additional information insertion signal is generated. It is characterized by being configured to perform stop control.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system block diagram of a data multiplexing apparatus according to an embodiment of the present invention, and FIG. 2 is a timing chart showing the operation thereof.

In the video encoding unit 1, an input video signal is encoded according to an encoding control signal VCNT output from the video encoding control unit 3 based on the transmission buffer occupation amount BOC from the buffer memory 4. This encoding includes, in addition to digitization, data compression processing as necessary.

The encoded data, together with the encoding control signal,
The data is multiplexed into a predetermined frame structure (hereinafter referred to as a video frame) and output to the buffer memory 4.

From the buffer memory 4, in accordance with a read control signal VRCNT from the buffer memory read control unit 5, video frame data is stored in VBR (Variable) in cell units.
BitRate) format (the details of the read control of the buffer memory will be described later).

The delay time of the video frame data generated by the buffer memory 4 is detected by the delay detection unit 10 and the delay information D is determined in advance by the delay information multiplexing unit 11 for each corresponding image frame. Multiplex to time slot. By using this information on the receiving side, the propagation delay time including the buffer memory of the encoded video data can be made constant.

As a method of detecting the delay time, for example, the difference between the times when the unique word indicating the head of each frame is detected at the input / output of the buffer memory 4 can be detected as the delay information D.

AAL (ATM Adaptation Layer) (V
The (BR) processing unit 6 attaches additional information such as an AAL header / trailer to the video frame data read out on a cell basis and outputs the video frame data to the cell multiplexing unit 8. The AAL processing unit 6 conforms to CCITT recommendation, I.P. 362, I. 363 is used to convert the data into cell data of a fixed length. Further, the AAL processing unit 6 outputs a signal CLCNT indicating a time slot period for inserting the additional information.
(Refer to FIG. 2A).
Output to

On the other hand, the audio encoding unit 2 digitally encodes the audio signal and converts the encoded data to AAL (CB).
R) Output in accordance with the read request signal ARCNT that is output from the processing unit 9 and that is at the sampling clock cycle.

[0027] The AAL
The (CBR) processing unit 7 attaches additional information for cell formation in the same manner as in the case of video, and outputs the added information to the cell multiplexing unit 8. This AAL processing unit 7 has the same CCI as the previous AAL processing unit 6.
TT Recommendation, I. 362, I. The data is converted into cell data of a fixed length according to a procedure based on H.363.

The AAL (VBR) processing unit 6 and the AAL (CB
R) Video / audio cell VCEL output from the processing unit 7
L and ACELL (see FIG. 2A) are multiplexed by the cell multiplexing unit 8 on a cell basis. However, “V−” in FIG.
VCELL and ACE, as in "2" and "A-1"
When LL occurs at the same time, ACE in CBR format is used.
LL is prioritized, VCELL cell multiplexing is stopped until ACELL cell multiplexing is completed, and a signal MUXCNT indicating the suspension period is output to the buffer memory read control unit 5 (see FIG. 2A).

The read control of the buffer memory 4 will be described in detail.
However, under the following conditions (1) to (4), control is performed using the VRCNT signal so as to stop reading from the buffer memory 4.

When the occupation amount of the transmission buffer becomes 0 by the BOC signal (the portion indicated by "0" at the BOC in FIG. 2A).

Time slot period for inserting additional information for cell formation (“H” portion of CLCNT in FIG. 2A).

Video / audio cell VCELL / ACEL
When L occurs simultaneously (V-2 and A-1 in FIG. 2A)
MUXCNT is "H" in the period).

As a result of the above processing, as shown in the output cell of FIG. 2A, the cell in the form of VBR (V-1, V-2...) And the cell in the form of CBR (A-1...) Can be multiplexed.

FIG. 2B shows an example of cell multiplexing. As can be seen from this figure, a cell that had to transmit a dummy data cell in the past (see FIG. 7) can be made a cell that can be used for other information as an empty cell.

FIG. 3 is a system block diagram of the cell separation device according to the present invention. A signal obtained by multiplexing the video encoded data cellized in the VBR format and the audio encoded data cellized in the CBR format is input to the cell separation unit 31. For the input signal, the cell separation unit 31 separates the cell into video encoded data cells (VBR format) and audio encoded data cells (CBR format) based on information in the cell header.

The video encoded data cell (VCELL) and the audio encoded data cell (ACELL) separated by the cell separation unit 31 are sent to the AAL (VBR) processing unit 32 and the AAL (CBR) processing unit 33, respectively. Is entered. These AAL processing units 32 and 33 perform processing in accordance with the CCITT recommendation, similarly to the AAL processing units 6 and 7 in FIG.

The AAL (VBR) processing section 32 separates valid data from additional information such as the header and trailer of the AAL from the input cell signal VCELL, and performs processing for erroneous cell / cell loss. Further, it outputs a signal VWCNT indicating a period of valid data to the video buffer memory 35.

Next, in the delay information separating section 34, AA
From the video coded data output from the L (VBR) processing unit 32, an effective data part is detected based on the above VWCNT signal (the output signal from the AAL (VBR) processing unit 2 includes:
Since additional information such as a cell header is included, only true data excluding the additional information is detected), and a frame structure (hereinafter referred to as a video frame) predetermined on the transmitting side is detected. Similarly, the information D of the delay of each video frame data generated by the buffer memory on the transmission side, which is multiplexed on the transmission side, is separated.

The video buffer memory 35 stores AAL (V
Out of the video encoded data (same as the video frame data) output from the BR) processing unit 32,
Only the valid data portion is written according to the T signal.

Regarding reading from the video buffer memory 35, the video buffer memory read control unit 36 determines whether or not the following conditions are satisfied. When the condition is satisfied, the read start signal VRST is output to the video buffer memory 35.
And start reading.

That is, this condition means that the buffer occupancy VBOC output from the video buffer memory 35 is A
Even if there is an occupation amount that does not cause an underflow even when a cell arrival delay of the TM network occurs, the delay amount D caused by the buffer memory on the transmission side and the video frame memory in which the delay amount D is multiplexed. 35 is equal to the sum of the delay and the predetermined delay amount T.
It is when it becomes HV. After starting reading,
Receiving the read request signal VRRQ from the video decoding unit 39, the data is read at any time.

The video coded data thus read out is decoded by the video decoding unit 39. By the above processing, the sum of the delay caused by the transmission / reception buffer memory for the video data becomes the above-mentioned THV.

On the other hand, the AAL (CBR) processing unit 33
From the input cell signal ACELL, the AAL header
Similarly, only valid data is separated from additional information such as a trailer, and processing for erroneous cell / cell loss is performed. Further, a signal AWCNT indicating a valid data period is output to the audio buffer memory 37.

AAL (CB) is stored in the audio buffer memory.
R) Of the audio encoded data output from the processing unit 33,
Only the valid data portion is written according to the AWCNT signal (the output signal from the AAL (CBR) processing unit 33 includes additional information such as a cell header).

Regarding reading from the audio buffer memory 37, the audio buffer memory read control unit 38 determines whether or not the following conditions are satisfied. When the condition is satisfied, the read start signal ARST is output to the audio buffer memory 37.
And start reading.

That is, the condition is that the buffer occupancy ABOC output from the audio buffer memory 7 is AT AT
This is the time when the occupation amount α is such that the underflow does not occur even if the cell arrival delay of the M network occurs.

After the start of reading, the read request signal ARRQ from the audio decoding unit 40 is received, and reading is performed at any time.

The voice coded data thus read out is
The audio is decoded by the audio decoding unit 40. By the above processing,
There is no transmission buffer memory in the audio data system, and the delay caused by the buffer memory is the delay amount THA corresponding to the occupation amount α. That is, since the audio data is read out from the buffer memory 37 only after the data is stored by the amount α that does not cause the underflow, the delay amount of the memory 37 is reduced until the occupation amount α. Equal to the time THA.

The delay difference between the video and audio data decoded by the above processing is obtained by encoding / decoding the difference between THV and THA, and the respective signals, except for the arrival delay fluctuation of each cell in the ATM network. If the delay difference is compensated by a decoding unit or the like, the synchronization between the video and the audio signal can be matched to the extent that there is substantially no problem.

[0050]

As described above, according to the present invention, VBR cells for video encoded data and CBR cells for audio encoded data are efficiently multiplexed. What has been transmitted can be made an empty cell, which is effective for transmitting other information.

Further, the data separating section on the receiving side adds the delay information of the video data generated in the buffer memory on the transmitting side for synchronizing the audio and the video, and transmits the data. Video cell data and CBR audio cell data are synchronized with each other (lip sync).
There is an effect that reproduction can be performed while maintaining the constant.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a data multiplexing device of the present invention.

2A is an operation time chart of the block in FIG. 1, and FIG. 2B is a diagram showing an example of multiplexing of ATM cells.

FIG. 3 is a block diagram showing an embodiment of the data separation device of the present invention.

FIG. 4 is a system block diagram of a conventional data multiplexing device.

FIG. 5 is a diagram showing a data multiplexing format in the block of FIG. 4;

FIG. 6 is a diagram illustrating an example of data multiplexing in the block of FIG. 4;

FIG. 7 is a diagram showing an example in which conventional multiplexed data is converted into ATM cells.

[Explanation of symbols]

 Reference Signs List 1 video encoding unit 2 audio encoding unit 3 video encoding unit control unit 4 buffer memory 5 buffer memory read control unit 6, 32 AAL (VBR) processing unit 7, 33 AAL (CBR) processing unit 8 cell multiplexing unit 10 delay Detecting unit 11 Delay information multiplexing unit 31 Cell separation unit 34 Delay information separation unit 35 Video buffer memory 36 Video buffer memory read control unit 37 Audio buffer memory 38 Audio buffer memory read control unit 39 Video decoding unit 40 Audio decoding unit

Claims (3)

(57) [Claims] 1. A video encoding means for encoding a video signal, a buffer memory for temporarily storing the encoded video output, and a read control means for reading data stored in the buffer memory for each fixed length video data. Delay detecting means for detecting a delay time in which the read video data is delayed by passing through the buffer memory; means for multiplexing the detected delay time information with the read data in the buffer memory; Cellular means for adding additional information such as a header and a trailer to each of the video data which is a coded output to form a cell and derive it, an audio coding means for coding an audio signal, and an audio coded output Means for adding the additional information such as a header and a trailer to each of the fixed-length sound data to form a cell, and derive these video cells and sound cells. And a cell multiplexing means for multiplexing and transmitting the multiplexed data. 2. The cell multiplexing means includes means for detecting the simultaneous occurrence of the audio cell and the video cell to generate a coincidence detection signal, and wherein the buffer memory means Means for detecting that the amount has become zero and generating a zero detection signal, wherein the video celling means generates a time slot period additional information insertion signal for inserting the additional information for cellization Means for reading out data from the buffer memory when at least one of the simultaneous detection signal, the zero detection signal, and the additional information insertion signal is generated. 2. The data multiplexing device according to claim 1, wherein: 3. A fixed-length cellized video cell data and a fixed-length cellized audio cell data are time-division multiplexed .
A data separation apparatus for separating multiplexed data in which delay time information is multiplexed with the video cell data, wherein the separation unit separates the video cell data and the audio cell data from the multiplexed data, respectively, Separating means for separating the delay time information from the video cell data; a video buffer memory for temporarily storing video data of the video cell data; a storage data amount of the video buffer memory;
Means for controlling reading of the video buffer memory in accordance with the delay time information , an audio buffer memory for temporarily storing audio data of the audio cell data, and an audio buffer memory for storing the audio buffer memory in accordance with an amount of data stored in the audio buffer memory. A data separating apparatus comprising: means for controlling reading; and means for decoding each read data of the video buffer memory and the audio buffer memory, respectively.