JPH04157826A - Data decoder - Google Patents

Abstract

PURPOSE:To improve the probability of the detection of a discarded cell by judging whether or not information regarding length when a cell contains data completely is equal to the length of data, which is obtained according information, in the last cell, on the length data that the cell right before the last cell can not contain and can not be contained in the last cell. CONSTITUTION:The length of data that the cell right before the last cell 1 can not contain is obtained from the information 2 regarding the length when the last cell l contains data in a single or plural frames completely and the information 3, that the last cell 1 contains, of data that the cell right before the last cell l can not contain, thereby judging whether or not information 6, that each cell 4 contains, on the length of data that the right cell 1 can not contain is equal to the length of data that the cell 1 right before the cell 4 can not contain. When there is a discarded cell following the last cell 1, the data lengths are not equal, so the presence of the discarded cell following the last cell 1 is detected with high accuracy.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a data decoding device provided on the receiving side of a transmission system that transmits frame data including audio sampling data in an asynchronous transfer mode using fixed-length cells, and is capable of detecting discarded cells. In order to improve the probability, an asynchronous transfer mode is used in which each frame includes one or more frames of data including audio sampling data generated at each predetermined time by sampling audio for a predetermined time. generating cells of a fixed length, each of which contains information regarding the length when each of the data of the one or more frames included in the cell is completely included; In a data decoding device provided on the receiving side of a transmission system that transmits data including data length information that could not be included in the immediately preceding cell among data of the last frame included in the cell, The information regarding the length when the data length information that could not be included in the immediately preceding cell completely includes data of one or more frames included in the immediately preceding cell; and means for determining whether the data length is equal to the data length that could not be included in the immediately previous cell, which is obtained based on information on the data length that could not be included in the immediately previous cell. Configure.

[Industrial application field]

The present invention relates to a data decoding device provided on the receiving side of a transmission system that transmits frame data including audio sampling data using fixed length cells.

In an audio signal transmission system using an asynchronous transfer mode (ATV), data of a frame containing audio sampling data generated at each predetermined time by sampling audio for a predetermined time is transmitted over one or more frames. Transmission is performed using fixed-length cells in an asynchronous transfer mode.

These cells are numbered in the order of voice signal generation on the transmitting side, but in asynchronous transfer mode, each cell reaches the receiving side via a different path on the network. , the cells may arrive at the receiving end in a different order than the order in which the voice signals were generated.

Furthermore, there may be cases where a switching device or the like on a network is inundated with a large amount of data at once and cannot handle it.

In such a case, cells are discarded.

On the receiving side, when cells are discarded as described above, it is necessary to detect this and perform silent processing.

Therefore, there is a need for a technique that can detect with high accuracy that cells have been discarded during the transmission process.

[Prior Art and Problems to be Solved by the Invention] An example of a conventional transmitter device using an asynchronous transfer mode for audio signals is an audio encoding device.

In the audio encoding device, the analog audio signal is
In the D conversion circuit, the data is sampled in synchronization with a sampling clock of a predetermined frequency, and in the encoding processing circuit, the sampling data for each predetermined time, for example, Ams, is taken as one frame, and for each frame, for example,
Encoding is performed at a coding rate of 16 to 48 kbps. The encoded data of each frame and the encoding rate of each frame are supplied to a cell generation circuit, where cells are generated. Here, a predetermined number of frames (for example,
7 frames), it is determined whether or not silent frames have been detected consecutively, and if silent frames have not been detected consecutively for a predetermined number of frames, the cell generation circuit:
A cell containing the encoded data and encoding rate from the encoding processing circuit described above is generated and sent onto a transmission path. Here, each cell has the number of the first frame included in each cell added as a cell number.

FIG. 6 shows the format of an ATM cell generated by the above cell generation circuit.

As shown in FIG. 6, in this example, each cell consists of a total of 53 bytes, and the first 5 bytes are an ATM header,
The next 4 bytes are an ADP header, followed by 44 bytes of encoded audio data.

FIG. 7 shows the structure of the ADP header shown in FIG. 6. As shown in FIG.
The above cell number is written in the byte, the encoding rate of each of the multiple (maximum 6 frames in this example) audio frames included in the cell is written in the area from the second byte to the lower two bits of the fourth byte, and the The area up to the upper 6 bits of the 4 bytes contains "intra-cell head position information". here,
"Intra-cell head position information" indicates the length of data that could not be included in the immediately previous cell, among the data of the last frame included in the cell generated immediately before the current cell. As described above, each cell has the number of the first frame included in each cell added as a cell number.

In this way, the data decoding device on the receiving side that receives the cells generated as described above uses the cell number (first frame number) assigned to each cell and the number of frames included in each cell. is the cell number (first frame number) attached to the next received cell.
Alternatively, it is possible to recognize that a discarded cell existed between data of two cells, and to perform silence processing in the data decoding device on the receiving side accordingly. Note that the number of frames included in each cell can be recognized from the (number of) encoding rate information for each of the multiple (maximum 6 frames in this example) audio frames included in the cell in the ADP header in FIG. I can do it.

However, since the above-mentioned frame number is indicated by a maximum of 8 bits, it is cyclical with respect to the maximum number indicated by 8 bits.

Therefore, even when a burst of discarded cells occurs, the sum of the cell number (first frame number) assigned to each cell and the number of frames included in each cell is assigned cell number (first frame number)
There was a problem that it could be the same as That is, there is a problem in that the data decoding device on the receiving side does not correctly detect discarded cells with a predetermined probability.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a data decoding device on the receiving side that improves the probability of detecting discarded cells.

[Means to solve the problem]

According to the first aspect of the present invention, an asynchronous transfer mode includes data of frames each containing audio sampling data generated at each predetermined time by sampling audio for a predetermined time over one or more frames. cells of a fixed length are generated, and each of the cells includes information regarding the length when each of the data of the frame or frames contained in the cell is completely included, and In a data decoding device provided on the receiving side of a transmission system that transmits data of the last frame included in the last frame including information on a data length that could not be included in the immediately preceding cell, each cell includes: The information on the data length that could not be included in the immediately preceding cell includes the information regarding the length when each of the data of one or more frames included in the immediately preceding cell is completely included; , and means for determining whether the data length is equal to the data length that could not be included in the immediately previous cell, obtained based on information on the data length that could not be included in the immediately previous cell. It is characterized by

According to the second aspect of the present invention, the audio sampling data includes audio sampling data that is generated at each predetermined time by sampling audio for a predetermined time and is numbered modulo a predetermined number in the order of generation. A fixed length cell of an asynchronous transfer mode is generated, each of which contains frame data over one or more frames, and each of the cells contains the frame number of the first frame of the one or more frames included in the cell, and the cell. information on the number of the single or multiple frames included in the cell, information on the length when each of the single or multiple frames included in the cell is completely included, and the data generated immediately before the cell. In a data decoding device installed on the receiving side of a transmission system that transmits data of the last frame included in a cell, including data length information that could not be included in the immediately preceding cell, the immediately preceding cell 10 is The number 52, which is supposed to be the first frame number of the current cell 15, is calculated from the information 13 of the number of frames included in the immediately previous cell 10 and the first frame number 14 included in the immediately previous cell 10. means 53 for comparing with the first frame number 19 of the cell 15 contained in the cell 15 to determine whether they match; and information contained in each cell 15 on data length that could not be contained in the immediately preceding cell 10; 17 is the cell 10 immediately before the cell 15
Information 11 regarding the length when the data of a single or plural frames are completely included, and the length of data contained in the immediately preceding cell 10 that could not be included in the immediately preceding cell 100 and the immediately preceding cell. It is characterized by comprising means 51 for determining whether or not the data length is equal to the data length 50 that could not be included in the immediately preceding cell 10, which is obtained based on the information 12 of the cell 10.

[For production]

FIG. 1 is an explanatory diagram of the principle of the first embodiment of the present invention. 1st
As shown in the figure, according to the first embodiment of the present invention, information 2 regarding the length when each of the data of a single frame or a plurality of frames included in the immediately preceding cell 1 is completely included.
The data length that could not be included in the immediately previous cell 1 can be obtained from the information 3 of the data length that the immediately previous cell 1 contains and that could not be included in the cell immediately before the immediately previous cell 1. Then, the information 6 of the data length that each cell 4 contains that could not be included in the cell 1 immediately before the cell 4 is equal to the data length that could not be included in the cell 1 immediately before the cell 4 obtained as described above. 8. If there is a discarded cell between the immediately preceding cell 1, the immediately preceding cell included in the above cell 4, unless there is a coincidence, the discarded cell Since the data length information 6 that could not be included in the cell 1 and the data length that could not be included in the immediately previous cell 1 obtained as described above no longer match, The presence of discarded cells is detected with high accuracy.

FIG. 2 is an explanatory diagram of the principle of the second embodiment of the present invention. Second
As shown in the figure, also in the second form of the present invention,
As in the first embodiment of the invention, the immediately preceding cell 10
Information 11 regarding the length when each of the single or plural frames included in the data is completely included, and the data length included in the immediately preceding cell 10 that could not be included in the immediately preceding cell 10. The data length that could not be included in the immediately preceding cell 10 is obtained from the information 12 of 50, and the information 17 of the data length that cannot be included in the immediately preceding cell 10, which is included in each cell 15, is obtained as described above. obtained,
Determine whether the data length is equal to the data length that could not be included in the cell 10 immediately before the cell 15.
If there is a discarded cell between them, the data length information 17 included in the cell 15 that could not be included in the immediately preceding cell 10 and the information 17 on the data length that could not be included in the immediately preceding cell 10 are When the data length that could not be included in the immediately preceding cell 10 obtained as shown in FIG. Ru.

In the second embodiment of the present invention, the above judgment 5 is further provided.
At the same time as the discarded cell detection according to No. 1, the discarded cell detection according to the conventional judgment described above is used in combination. That is, the number of frames included in the immediately preceding cell 10 is 13.
and the first frame number 14 included in the immediately previous cell,
Find the number that should be the starting number of the frame included in the current cell 15 52° Then, find the number that should be the starting number of the frame included in the current cell 15. Compare with the first frame number 19 to determine whether they match. 53 If the previous cell 1
0, if there is a discarded cell, it cannot be included in the immediately preceding cell 10 included in the above cell 15, except in cases where there is a coincidence due to burst discard etc. as described above. The data length information 17 obtained in the above manner does not match the data length that could not be included in the immediately preceding cell 10 (as a result, the discarded cell between the immediately preceding cell 10 is detected.

Thus, according to the second aspect of the invention, the first aspect of the invention
The accuracy of discarded cell detection can be improved by simultaneously using discarded cell detection using the above-described conventional judgment method.

〔Example〕

As an embodiment of the present invention, an embodiment of the above-described second embodiment of the present invention will be shown. From the foregoing description, it will be clear that if the second aspect of the invention can be realized, the first aspect of the invention can also be realized. As an embodiment of the present invention, the sixth
Before using the formats shown in FIG. 7 and FIG. 7, a data decoding apparatus for receiving cells and decoding them into audio signals as described in the "Prior Art" section will be described.

FIG. 3 is a diagram showing the configuration of a data decoding device according to an embodiment of the present invention.

In FIG. 3, 21 is a header/data separation circuit, 22
23 is a frame number recognition circuit, 23 is a rate information judgment circuit,
24 is a cell head position recognition circuit, 25 is a data buffer, 26 is a silence processing circuit, 27 is a rate information processing/reading control circuit, 28 is a format conversion circuit, 29 is a discarded cell detection circuit, and 30 is a selector. .

The cells having the format shown in FIG. 6 are separated in the header/data separation circuit 21, and the separated data portion (encoded data) is supplied to the data buffer 25.
The ADP header is processed by a frame number recognition circuit 22, a rate information determination circuit 23, and an intra-cell head position recognition circuit 24.
is supplied to

The frame number recognition circuit 22 recognizes the cell number in the format shown in FIG. The rate information judgment circuit 23
The number of frames included in the cell and the data length (total length) of each frame are detected from the encoding rate information in the format shown in FIG. The in-cell head position recognition circuit 24 recognizes the above-mentioned "in-cell head position information."

The rate information processing/reading control circuit 27 reads out the encoded data held in the data buffer 25 based on the above-mentioned encoding rate information and "intra-cell head position information" and converts it into a format conversion circuit. Supply to 28. The format conversion circuit 28 decodes the supplied encoded data. The decoded audio signal is outputted from the data decoding device via the selector 30.

The rate information processing/reading control circuit 27 detects how many bytes of data in the final frame of each received cell actually remain (which is not included in the cell concerned, but should be included in the next cell), and This information is supplied to the discarded cell detection circuit 29.

In the discarded cell detection circuit 29, the above-mentioned cell number and encoding rate information are input, and as in the conventional case,
The cell number (first frame number) assigned to each cell,
In addition to detecting discarded cells by determining whether the sum of the number of frames included in each cell matches the cell number (first frame number) assigned to the subsequently received cell,
Furthermore, input the cell head position information J and compare it with the information on how many bytes of data in the last frame of the cell actually remain, supplied from the rate information processing/read control circuit 27. If these pieces of information do not match, it is assumed that there is a discarded cell between the two cells, and
The silence processing circuit 26 is controlled to perform silence processing. The silence processing circuit 26 supplies an audio signal at a silence level to one input terminal of the selector 30 for a predetermined period of time in response to the determination that there is a discarded cell. At this time, the discarded cell detection circuit 29 controls the selector 30 so that the data decoding device selects and outputs the silent audio signal, and also performs rate information processing. /The read control circuit 27 is controlled to stop the decoding process in the format conversion circuit 28 for the above-mentioned predetermined time.

FIG. 4 is a flowchart showing the above procedure.

FIG. 5 is a diagram showing an example of cell generation operation in the data decoding device of FIG. 3.

In Fig. 5, A, B, C,... are shown as:
The data of the voice frames generated on the transmitting side is encoded at a coding rate of 16 kbps to 32 kbps, respectively, as shown. Here, the total length of one frame of data encoded at a coding rate of 16 kbps is 8 bytes,
The total length of one frame of data encoded at 24 kbps is 12 bytes, and the encoding rate is 32 kbps.
The total length of one frame of data encoded in bps is 16
It's a part-time job. Further, the encoding rate of each frame is included in the ADP header of FIG. 7 in the form of an encoding information code as shown in FIG.

As shown in FIG. 6, since the data contained in one cell is 44 bytes, A, B, and C in FIG.
, and up to the data of the frame D are included in the first cell, leaving the last 4 bytes of the data of the frame D, and from the last 4 bytes of the data of the corresponding frame to the frame J The data up to J are included in the second cell, except for the last 4 bytes of the data in frame J. Here, as the "intra-cell start position information" in the first cell, the initial value of "in-cell start position information" is "0".
is included, and the above-mentioned value "4 (byte)" is included as "intra-cell head position information" in the second cell.

The rate information processing/reading control circuit 27 in FIG. 3 reads all the encoding rate information of the first cell and calculates the data of frame D by counting or calculating as shown in FIG. It recognizes that the last 4 bytes are not included in the cell of box 1 and supplies this information to the discarded cell detection circuit 29. This information is compared with the "intra-cell leading position information" of the next cell when it is read into the discarded cell detection circuit 29, and if they do not match, the discarded cell is It recognizes that there is a sound, and performs the silent processing. On the one hand, the discarded cell detection circuit 29 detects the cell number (
Discarded cells are also detected by determining whether the sum of the first frame number) and the number of frames included in each cell matches the cell number (first frame number) assigned to the subsequently received cell. . In the example shown in FIG. 6, since a match is detected between the first and second cells in both of the above two determinations, it is determined that no discarded cell was detected. .

〔Effect of the invention〕

According to the data decoding device of the present invention, it is possible to improve the probability of detecting discarded cells.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle of the first embodiment of the invention, FIG. 2 is an explanatory diagram of the principle of the second embodiment of the invention, and FIG. 3 is a diagram illustrating the configuration of a data decoding device according to an embodiment of the invention. 4 is a diagram showing a cell generation operation procedure in a data decoding device according to an embodiment of the present invention, FIG. 5 is a diagram illustrating an example of a cell generation operation in a data decoding device according to an embodiment of the present invention, FIG. 6 is a diagram showing the format of an ATM cell, and FIG. 7 is a diagram showing the structure of the ADP header in FIG. [Explanation of symbols] 21...Header/data separation circuit, 22...Frame number recognition circuit, 23...Rate information judgment circuit, 24...Intra-cell head position recognition circuit, 25...Data bar... 26...silence processing circuit, 27 is a rate information processing/reading control circuit, 28...
formant conversion circuit, 29... discarded cell detection circuit, 30... selector. Diagram showing cell format 5 bits

Claims (1)

[Scope of Claims] 1. A fixed length in an asynchronous transfer mode that includes data of a frame containing audio sampling data generated at each predetermined time by sampling audio for a predetermined time, each spanning one or more frames. cells, and each of the cells includes information regarding the length when each of the data of the single or plural frames included in the cell is completely included, and the cell generated immediately before the cell. In a data decoding device installed on the receiving side of a transmission system that transmits data including the data length information that could not be included in the immediately preceding cell among the data of the last frame, each cell (4) includes the above-mentioned The data length information (6) that could not be included in the immediately preceding cell is information (2) regarding the length when each of the data of one or more frames included in the immediately preceding cell (1) is completely included. , in the immediately preceding cell (1) obtained based on the data length information (3) included in the immediately preceding cell (1) that could not be included in the immediately preceding cell (1). A data decoding device characterized by comprising means (8) for determining whether the data length is equal to the data length (7) that could not be included. 2. The data of the frame containing the audio sampling data generated at each predetermined time by sampling the audio for a predetermined time is encoded at the encoding rate of each frame, and each is encoded into one or more frames. Generate fixed-length cells in an asynchronous transfer mode containing across frames, each of the cells containing the encoding rate of the data of each frame included in the cell, and the last frame included in the cell generated immediately before the cell. In a data decoding device installed on the receiving side of a transmission system that transmits the data including the data length information that could not be included in the immediately preceding cell, the The information on the data length that was not included is the encoding rate of the data of each frame included in the immediately preceding cell, and the information on the data length that was included in the immediately preceding cell and could not be included in the cell immediately preceding the immediately preceding cell. A data decoding device comprising means for determining whether or not the data length obtained based on the data length is equal to the data length that could not be included in the immediately preceding cell. 3. Sampling the audio for a predetermined period of time generates each frame of data at a predetermined time interval, and the frame data is numbered modulo a predetermined number in the order of generation. A cell of a fixed length in an asynchronous transfer mode that spans a frame is generated, and each of the cells includes the frame number of the first frame of the single or multiple frames included in the cell, and the frame number of the first frame of the single or multiple frames included in the cell. information on the number of frames, information on the length when each of the data of the single or multiple frames included in the cell is completely included, and information on the length of the data of the last frame included in the cell generated immediately before the cell. home,
In a data decoding device installed on the receiving side of a transmission system that transmits information including data length information that could not be included in the immediately preceding cell, the immediately preceding cell (10) includes a frame of the immediately preceding cell. The number (52) that should be the first frame number of the current cell (15) is calculated from the number information (13) and the first frame number (14) included in the immediately previous cell (10).
) is compared with the first frame number (19) of the cell (15) contained in the cell (15) to determine whether or not they match; The data length information (17) that could not be included in a cell relates to the length when each of the data of the single or plural frames included in the cell (10) immediately before the cell (15) is completely included. The immediately preceding cell obtained based on the information (11) and the information (12) of the data length included in the immediately preceding cell (10) that could not be included in the immediately preceding cell of the immediately preceding cell (10). A data decoding device comprising means (51) for determining whether the data length (50) is equal to the data length (50) that could not be included in the cell (10). 4. For each frame, frame data containing audio sampling data that is generated every predetermined time by sampling audio for a predetermined time and is numbered modulo a predetermined number in the order of generation. A fixed-length cell of an asynchronous transfer mode is generated, each of which contains data encoded at a coding rate of Information on the frame number, the encoding rate of the data of each frame included in the cell, and the length of data that could not be included in the previous cell among the data of the last frame included in the cell generated immediately before the cell. In a data decoding device provided on the receiving side of a transmission system that transmits information including information on the number of frames of the immediately preceding cell included in the immediately preceding cell, and the first frame number included in the immediately preceding cell, means for determining whether or not the number that is supposed to be the first frame number of the current cell, calculated from the cell, matches the first frame number of the cell included in the cell; The information on the data length that could not be included in the immediately preceding cell is the encoding rate of the data of each frame included in the immediately preceding cell, and the data in the immediately preceding cell included in the immediately preceding cell. and means for determining whether or not each cell is equal to the data length that could not be included in the cell immediately preceding each cell, which is obtained based on the information on the data length that could not be included. conversion device.