JP2002009870A - Data transmitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data transmitting device which emits no abnormal sound outside even if the parameter of a transmission signal changes during data transmission and is restored. SOLUTION: In the data transmitting device, transmission data including at least a compressed digital sound signal is transmitted from a transmission part and a reception part expands/decodes it and obtains original data. When the transmission part detects switching of a prescribed parameter on transmission data, respective flags corresponding to the change contents of the detected parameters are added to the corresponding headers of transmission data and they are transmitted. When the flag corresponding to the change content of the prescribed parameter is detected by the reception part, the resetting of the expansion/decoding of the reception part or the muting processing of output data is performed based on the detected flag.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a data transmission apparatus including a digital audio compression signal, a digital television broadcast, and a digital audio broadcast transmission apparatus.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a conventional data transmission apparatus including a digital audio compression signal, which will be described below. In the transmission section Tx, the analog audio signal input is converted into a digital PCM signal by the A / D converter 1 and enters the compression encoder 2. Here, the audio signal is compressed to produce an encoded signal. As a compression encoding method, a commonly used MPEG1 audio encoding method,
There are an MPEG2 audio coding method, an AC-3 coding method and the like, but any method may be used. The audio data encoded by the compression encoder 2 is stored in a buffer 3 and is extracted according to a clock read from a channel encoder 4 at the next stage. The channel encoder 4 performs time division multiplexing with another transmission signal and forms an output transmission signal into a predetermined format, for example, a transport stream (TS). Then, this output signal is sent to the receiving unit Rx through the transmission path 5. The transmission path 5 uses a conductor cable, an optical cable, and a microwave in a general transmission line, and uses radio waves in broadcasting. Receiver R
At x, the transmitted multiplexed signal is separated by the channel decoder 6 and sent to the expansion decoder 8 via the buffer 7. The compressed audio data sent to the buffer 7 is temporarily stored here, and is extracted by the read clock from the expansion decoder 8. The decompression decoder 8 operates to receive the compression-encoded data, decode it, and restore it to a digital PCM signal. The restored PCM signal is converted into an analog audio signal by the D / A converter 9 and becomes an output signal of the receiving unit Rx.

[0003] If data is transmitted using such a device and the data is continuously transmitted by switching the parameters of the digital audio signal or the parameters of the compressed data, the following problems occur. there is a possibility.
Here, parameter switching refers to switching the sampling frequency, the number of sampling bits, the number of channels (monaural, dual monaural, stereo, multi-stereo, etc.), the bit rate of compressed data to different values, and the like. 1) When the parameters are switched, an abnormal sound is generated in the audio output. 2) When the parameters are switched, the operation of the decompression decoder 8 stops, and there is no sound output. 3) When the parameters are switched, the buffer 7 breaks down due to underflow or overflow, and audio output stops. Any of the above three phenomena is a problem that seriously hinders voice transmission.

[0004]

Here, when these phenomena occur, what countermeasures have been taken so far and where the problems of the countermeasures have been are described. 1) Countermeasures when abnormal sound occurs in audio output In such a transmission device, CRC (Cyclic Redundant) is used.
ancy Code (cyclic redundancy code) Error detection is performed.
This is a method in which 1-bit detection data is added to data having a structure that circulates at a fixed period to detect an error due to transmission, and the receiving unit detects the error. In FIG. 2, the data input to the decompression decoder 8 is
An error check is performed by the CRC error detector 10. If an error is detected, a mute signal is sent to the D / A converter 9. Thereby, the D / A converter 9
Is controlled not to output abnormal noise due to data errors. The problem here is that the CRC error detection is not sufficiently reliable and may generate abnormal noise. 2) Countermeasures when the operation of the decompression decoder 8 stops and the audio output stops. The countermeasure when the decoding operation is abnormal due to the parameter change and the data decoding is stopped is as shown in FIG. The output 8 is checked by the output detector 11, and if no output is output for a certain period of time, the decompression decoder 8 and the buffer 7 are reset to recover the decoding operation. The problem here is that it has been confirmed that abnormality is detected from the output signal of the decompression decoder 8 and that there is no data for a certain period of time to detect the abnormality. Cost. Therefore, there is a disadvantage that the period during which no output sound is output becomes longer. 3) Countermeasures when the buffer 7 fails and the audio output is lost The buffer 7 fails due to the parameter change,
Since the data cannot be sent to the decompression decoder 8, the decompression
Output data is lost. In such a case, the output detector 11 of FIG. 2 detects this, and resets the buffer 7 and the decompression decoder 8. As a result, the buffer 7 comes out of the failure state and starts operating from the initial state. The problem here is that an abnormality is detected by confirming that there is no data in the output signal of the decompression decoder 8 for a certain period of time, as in 2) above. Therefore, much time is required until a reset signal is issued. Therefore, there is a disadvantage that the period during which no output sound is output becomes longer as in 2). Conventionally, a countermeasure at the time of the above-mentioned abnormality has been performed in the receiving unit, and a method of taking a countermeasure after detecting an abnormality in the receiving unit has been adopted. The time required for this processing includes the time from when the output of the decompression decoder 8 becomes abnormal to the time when the output detector 11 confirms the abnormality, the time required for resetting, and the data which does not break down in the buffer 7. Time. The present invention eliminates these drawbacks, and prevents abnormal noise from being output to the outside even when the parameters of a transmission signal are changed in the middle of data transmission. However, the purpose is to recover in as short a time as possible.

[0005]

According to the present invention, in order to achieve the above-mentioned object, transmission data including at least a compressed digital audio signal is transmitted from a transmission unit, which is decompressed and decoded by a reception unit to obtain the original data. In the data transmission device, when the transmission unit detects the switching of the predetermined parameter related to the transmission data, each flag corresponding to the detected change of the predetermined parameter is added to the corresponding header of the transmission data. In addition, when the reception unit detects a flag corresponding to the content of the change of the predetermined parameter, based on the detected flag, at least a process of resetting the decompression decoding of the reception unit and a process of muting the output data are performed. Either of them is performed. Also, the transmitting unit checks header contents of the compressed data and detects switching of the predetermined parameter, and transmits the respective flags corresponding to the detected changed contents of the predetermined parameter to the transmitting unit. Means for adding to a corresponding header of data, the receiving unit detects a flag corresponding to the content of the change of the predetermined parameter, and at this time, at least reset processing of decompression decoding of the receiving unit, muting of output data It has a configuration including a header detecting means for generating a control signal for performing any of the processes. Further, the transmission unit checks the operation of the decompression decoding means for decoding the compressed data and the operation of the decompression decoding means. When the operation of the decompression decoding means is stopped, the decompression decoding of the reception unit is performed. A reset flag for performing a reset process is configured to include a unit for adding a mute flag for muting the output data of the receiving unit to a corresponding header of the transmission data when the decompression decoding unit emits abnormal noise. is there. Further, the switching of the predetermined parameter is to switch any one or more of the sampling frequency, the number of sampling bits, the number of channels, and the bit rate of the compressed and transmitted data to different values. That is, in the present invention, the occurrence of an abnormality is detected on the transmitting side, and when an abnormality is detected, the abnormality is transmitted to the receiving unit using the flag bit in the transmission data. It is possible to know that the error has occurred, and at that time, it is possible to perform processing according to the content of the abnormality. Therefore, the time required for the processing is the sum of the time required for the reset and the time required to accumulate data that does not break down in the buffer. As a result, according to the present invention, it is possible to recover from an abnormal state in a shorter time even when the parameters of a transmission signal are switched during data transmission, as compared with the conventional method.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a decoder reset method of a compression transmission apparatus according to the present invention will be described in detail with reference to a block diagram shown in FIG. In the transmission section Tx, the analog audio signal input is converted into a digital PCM signal by the A / D converter 1 and enters the compression encoder 2. Here, the audio signal is compressed and converted into encoded data. As the compression encoding method, there are an MPEG1 audio encoding method, an MPEG2 audio encoding method, an AC-3 encoding method, and the like, which are generally used, but any method may be used. The encoded data is divided into three parts, and the main line data is stored in the buffer 3. The stored voice data is extracted in synchronization with the read clock sent from the next channel encoder 4 and sent to the channel encoder 4. The channel encoder 4 time-division multiplexes the audio data with another transmission signal such as an image signal to form an output transmission signal arranged in a predetermined format. For the other two of the distributed encoded data, one goes to the header detector 12,
The other one is sent to a decompression decoder 13 which is a local decoder. The header detector 12 always checks the header content of the input coded data and monitors the parameters of the transmission data. The header detector 12 includes, among many parameter changes, a change in which an abnormal sound is generated in the reception unit Rx, a change in which the operation of the decompression decoder 8 is stopped, and a change in the buffer 7.
The content of the change that causes the failure is registered in advance. As a result, when a parameter change corresponding to the above occurs, the header detector 12 detects a parameter change from the header content of the input coded data, and if this is a change that produces abnormal noise, If the change of the mute control signal M1 is such that the operation of the decompression decoder 8 is stopped and the buffer 7 is broken, a first process of sending the reset control signal R1 to the channel encoder 4 is performed.

On the other hand, the decompression decoder 13 of the local decoder
The encoded data sent to is decoded immediately, and the operation of the decompression decoder 13 is checked. Here, the reset control signal R2 is sent to the channel encoder 4 when the operation of the decompression decoder 13 is stopped by the parameter change, and the mute control signal M2 is sent to the channel encoder 4 when the decompression decoder 13 emits abnormal noise. Perform processing. In the channel encoder 4, the reset control signals R1 and R2 and the mute control signals M1 and M2 sent in the first processing and the second processing are combined by an AND logic circuit or an OR logic circuit (not shown), Using the 2-bit data in the header of the transmission data, the receiver Rx is used as a reset flag and a mute flag.
Transmit to In the receiving section Rx, when these flags are detected by the header detector 15, the corresponding reset control signal R
3. Output the mute control signal M3 to the decompression decoder 8, the buffer 7, and the D / A converter 9. As a result, the operation of the decompression decoder 8 is stopped, and the buffer 7 is broken.
Normal operation can be restored, and operation is performed so that abnormal noise does not occur in the output of the receiving unit.

In FIG. 1, the reset control signal R3 is also sent from the header detector 15 to the channel decoder 6, which means that the channel decoder 6 remains stopped due to parameter change. It is to prevent. Similarly, the output data of the decompression decoder 13 of the transmission unit Tx is detected, and when the output is lost, a reset signal is sent from the output detector 14 to the decompression decoder 13. This is to prevent the state from being reached. As described above, conventionally, a countermeasure when an abnormal state occurs is performed by the receiving unit, and a countermeasure process is performed after detecting the abnormality in the receiving unit. Therefore, the time required for processing is the sum of the time from when the output of the decompression decoder becomes abnormal to the time when the detector confirms an error, the time required for resetting, and the time for storing data that does not break down in the buffer. become. On the other hand, in the present transmission device, the time required for the recovery process after the reception of the abnormality flag by the receiving unit is a time obtained by adding the time required for reset and the time for storing data that does not fail in the buffer 7, and Compared with the conventional method, the time from when the output of the decompression decoder becomes abnormal to when the output detector confirms the abnormality becomes unnecessary. As a result, the transmission device can recover from the abnormal state in a short time.

[0009]

According to the present invention, a method is employed in which the occurrence of an abnormality is detected on the transmitting side, and when an abnormality is detected, the abnormality is transmitted to the receiving unit using a flag bit in the transmission data.
The receiving unit can know that an abnormality has occurred at the same time as the data signal, and at that time, can perform processing according to the details of the abnormality. Therefore, the time required for the processing is the sum of the time required for the reset and the time required to accumulate data that does not break down in the buffer. As a result, compared with the conventional method, the present invention can eliminate the time from when the output of the decompression decoder becomes abnormal to when the output detector confirms the abnormality, and switch the parameters of the transmission signal. Even at times, it is possible to recover from an abnormal state in a short time.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a compression transmission device according to the present invention.

FIG. 2 is a block diagram illustrating a configuration of a conventional compression transmission device.

[Explanation of symbols]

2: compression encoder, 3, 7: buffer, 4: channel encoder, 6: channel decoder, 8, 13: decompression decoder,
12, 15: header detector, 14: output detector, D / A
converter.

Claims (4)

[Claims] 1. A data transmission apparatus for transmitting transmission data including at least a compressed digital audio signal from a transmission unit, and expanding and decoding the data in a reception unit to obtain original data. When the switching of the related predetermined parameter is detected, each flag corresponding to the detected change of the predetermined parameter is added to the corresponding header of the transmission data and transmitted, and the receiving unit transmits the predetermined parameter. When a flag corresponding to the content of change is detected, at least one of a resetting process of decompression decoding of the receiving unit and a mute process of output data is performed based on the detected flag. 2. The apparatus according to claim 1, wherein said transmitting section checks header contents of said compressed data and detects switching of said predetermined parameter, and said detected content of said changed predetermined parameter is changed. Means for adding each corresponding flag to a corresponding header of the transmission data, and detecting, in the receiving section, a flag corresponding to the change content of the predetermined parameter, at least expanding the receiving section. A data transmission device comprising: a header detection unit that generates a control signal for performing one of a decoding reset process and an output data mute process. 3. A decompression decoding unit according to claim 1, wherein said transmission unit includes a decompression decoding unit for decoding said compressed data.
The operation of the decompression decoding means is checked. When the operation of the decompression decoding means is stopped, a reset flag for resetting the decompression decoding of the receiving unit is set. A data transmission device, comprising: means for adding a mute flag for muting output data of a receiving unit to a corresponding header of the transmission data. 4. The method according to claim 1, wherein the switching of the predetermined parameter includes setting at least one of the sampling frequency, the number of sampling bits, the number of channels, and the bit rate of the compressed and transmitted data. A data transmission device for switching to a different value.