JPH0787126A - Data multiplex device - Google Patents

Abstract

PURPOSE:To effectively multiplex data when voice and video data are multiplexed corresponding to the ATM network. CONSTITUTION:A video signal is encoded by a video encoding part 1 and the ATM cell processing is performed by a buffer memory 4 and an AAL processing part 6. The voice signal is encoded by a voice encoding part 2 and the ATM cell processing is performed by an AAL processing part 7. A cell multiplex part 8 multiplexes the ATM cells by giving the priority to the voice ATM cell and the cells are sent. Thus, the video and voice cells are effectively multiplexed and when an idle cell occurs, the part can be used for the other data transmission.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data multiplexer, and more particularly, to a voice / video coded data multiplexer in a multimedia system compatible with an ATM (Asynchronous Transfer Mode) communication system.

[0002]

2. Description of the Related Art FIG. 3 shows a schematic configuration of a conventional audio / video coded data multiplexing apparatus in a multimedia system. In the figure, the input video signal is the video encoding unit 1
Is converted into digital data, and if necessary, data compression processing is performed and the data is derived to the buffer memory 4.

At this time, in the video coding unit 1, the input video signal is coded according to 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. It

The coded video data is input to the buffer memory 4 and temporarily stored therein, and then read according to the 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 in the same manner as the encoded video data.
It is output according to CNT.

In the multiplexer 9, the read request signal VRCN
Based on T and ARCNT, encoded data of video and audio is multiplexed in a fixed time slot (TV, TA: see FIG. 4) within a fixed cycle T.

However, since the amount of generated information of the video coded data changes with time, in order to eliminate the loss of the coded data, the number of time slots assigned to the video coded data is set to the TV time of FIG. Buffer memory 4 in
It is necessary to set the maximum amount of information output from.

As a result, when the amount of generated information of the video coded data between the TVs is small and the allocated time slot is less than the allocated time slot, dummy data is inserted by the multiplexer 9 as shown in FIG. It has become.

In such a conventional data multiplexing system, it is necessary to insert dummy data as shown in FIG.
When data is transmitted in a cell type having a fixed length like the M network, it is necessary to convert dummy data into cells and transmit the cells as shown in FIG.

Therefore, although the dummy data cell portion can be used for transmitting other data, it cannot be used and the transmission efficiency is deteriorated.

An object of the present invention is to provide a data multiplexer suitable for multimedia communication compatible with an ATM communication system by efficiently multiplexing audio data and video data.

[0012]

A data multiplexing apparatus according to the present invention comprises a 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. Readout control means for reading out each fixed length video cell data, video cellization means for adding additional information such as a header or trailer to each of the video cell data to derive the cells, and audio signals are encoded. A voice coding means for converting the voice coded output into a cell by adding additional information such as a header or trailer to each of the voice cell data of the fixed length, and deriving the voice cell output; And cell multiplexing means for multiplexing and transmitting cells.

[0013]

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

FIG. 1 is a system block diagram of an embodiment of the present invention, and the same portions as those in FIG. 3 are designated by the same reference numerals.

In the video encoding unit 1, the input video signal is encoded according to the 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. In addition to digitization, this encoding further includes data compression processing as required.

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

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

AAL (ATM Adaptation Layer) (V
The BR) processing unit 6 adds the additional information such as the AAL header / trailer to the video frame data read in cell units and outputs the video frame data to the cell multiplexing unit 8. The AAL processing unit 6 converts the data into cell data of a fixed length by a procedure based on CCITT Recommendation, I.362,363. Further, the AAL processing unit 6 outputs the signal CLCNT (see FIG. 2A) indicating the period of the time slot for inserting the additional information to the buffer memory read control unit 5.

On the other hand, in the voice encoding unit 2, the voice signal is digitally encoded and the encoded data is converted into AAL (CB).
R) (Constant Bit Rate) read request signal ARCN output at the sampling clock cycle output from the processing unit 7
Output according to T.

For this voice coded data, AAL
In the (CBR) processing unit 7, additional information for cell formation is added as in the case of video, and is output to the cell multiplexing unit 8.
This AAL processing unit 7 also has the same CC as the previous AAL processing unit 6.
ITT Recommendation, I. 362, I.D. Data is made into cell data of a fixed length by the procedure based on 363.

AAL (VBR) processing unit 6 and AAL (CB)
R) Video / audio cell VCEL output from the processing unit 7
L-ACELL (see FIG. 2A) is multiplexed in cell units by the cell multiplexer 8. However, in FIG.
VCELL and ACE, like the 2 "and" A-1 "parts
When LLs occur at the same time, ACE in CBR format
LL is given priority, cell multiplexing of VCELL is stopped until cell multiplexing of ACELL is completed, and a signal MUXCNT indicating the suspension period is output to the buffer memory read control unit 5 (see FIG. 2A).

The details of the read control of the buffer memory 4 will be described below.
However, under the following conditions (1) to (4), the buffer memory 4 is controlled using the VRCNT signal to stop reading.

When the transmission buffer occupancy becomes 0 due to the BOC signal (the portion indicated by "0" in the BOC of FIG. 2A).

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

Video / audio cell VCELL / ACEL
When L occurs at the same time (V-2 and A-1 in FIG.
In the period of, MUXCNT is the part of "H").

As a result of the above-mentioned processing, as shown in the output cell of FIG. 2 (A), a cell formed in the VBR format (V-1, V-2 ...) And a cell formed in the CBR format. It is possible to multiplex what has been done (A-1 ...).

FIG. 2B shows an example of cell multiplexing. As can be seen from this figure, the cell that conventionally had to transmit the dummy data cell (see FIG. 6) can be made into a cell that can be used for other information as an empty cell.

[0028]

As described above, according to the present invention, VBR format cells for video coded data and CBR format cells for audio coded data are efficiently multiplexed. An empty cell can be made where a cell had to be transmitted, and other information can be transmitted.

[Brief description of drawings]

FIG. 1 is a system block diagram of an embodiment 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 ATM cells.

FIG. 3 is a schematic block diagram showing an example of a conventional data multiplexing device.

FIG. 4 is a diagram showing a data multiplexing format in the blocks of FIG.

5 is a diagram showing an example of data multiplexing by the blocks of FIG.

FIG. 6 is a diagram showing an example in which conventional multiplexed data is converted into ATM cells.

[Explanation of symbols]

 1 Video Coding Section 2 Audio Coding Section 3 Video Coding Control Section 4 Buffer Memory 5 Buffer Memory Read Control Section 6 AAL (VBR) Processing Section 7 AAL (CBR) Processing Section 8 Cell Multiplexing Section

Claims (2)

[Claims] 1. A video coding means for coding a video signal, a buffer memory for temporarily storing the coded output of the video signal, and a read control means for reading the data stored in the buffer memory for each fixed length of video cell data. A video cellizing means for adding additional information such as a header or trailer to each of the video cell data to derive a cell, a voice coding means for coding a voice signal, and a voice coding output. Voice cell conversion means for adding additional information such as a header or trailer to each of the fixed length voice cell data and deriving the cells, and cell multiplexing means for multiplexing and transmitting the video cells and the voice cells. A data multiplexing device comprising: 2. The cell multiplexing means includes means for detecting that the audio cell and the video cell are simultaneously generated and generating a simultaneous detection signal, and the buffer memory means stores the stored data. The video cell conversion means generates a time slot period additional information insertion signal for inserting the additional information for the cell conversion. The read control means is configured to stop the data read from the buffer memory when at least one of the coincidence detection signal, the zero detection signal and the additional information insertion signal is generated. The data multiplexing device according to claim 1, wherein