JPH11313011A - Digital signal transmission system and signal transmission equipment therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable effective error compensation even in the case of a burst error and the case of receiving the information of a little correlation in time base direction. SOLUTION: At signal transmission equipment 20 on the side of reception, the presence/absence of any code error in the received signals of left and right channels is respectively discriminated by error detectors 22L and 22R and when the code error is detected on one channel (right channel R, for example,) in any arbitrary transmission frame, a switching control signal is outputted from this error detector 22R and a signal selecting switch 24R on the error detected side is switched to the side to select a decoded frame signal on the side of the other channel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal transmission system using, for example, a wireless transmission path, and more particularly to a method of transmitting information signals of a plurality of channels having correlation with each other, such as digital stereo broadcasting and multimedia information transmission. TECHNICAL FIELD The present invention relates to a digital signal transmission system for transmitting data via a communication device and a signal transmission device for the digital signal transmission system.

[0002]

2. Description of the Related Art In recent years, in the field of radio broadcasting and communication, various systems have been developed in which a transmission signal is converted into a digital signal for each channel, and the digital signal is wirelessly transmitted using a code decoding technique and a digital modulation / demodulation technique. Or has been proposed.

When transmitting a transmission signal by digital radio,
It is necessary to protect a transmission signal from code errors due to fading or the like, and various error control techniques are used for that purpose. For example, in a mobile communication system such as a mobile phone system, a transmitting station voice-encodes a speech signal, then performs error correction coding using an error correction code, digitally modulates a carrier signal with the coded signal, and transmits the signal. Then, the receiving station digitally demodulates the received signal, performs error correction decoding processing on the demodulated signal to correct a code error, and then reproduces the speech signal by voice decoding.

Further, in the monaural audio broadcasting system, for example, when an error is detected in the reception information of the current frame, the current frame in which the error is detected is replaced with the sound reception information of the previous frame, or the past frame is replaced. A method of compensating for errors by estimating correct information based on received information has been used.

[0005]

However, a system using an error correction code is generally effective for a small number of code errors, but may not be effective for a burst error. Also, in the method of reproducing received information based on past received frames, it is effective if the correlation between the current frame to be reproduced and the past received frame is large, but the effectiveness is low if the correlation is small. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its object is to provide an effective quality even for a burst error and when receiving information having a small correlation in the time axis direction. An object of the present invention is to provide a digital signal transmission system capable of performing compensation and a signal transmission device thereof.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a system for transmitting a plurality of signals, such as a digital stereo broadcast, in which there is a correlation between a plurality of transmitted signals. Pay attention to, in the signal transmission device on the receiving side, monitor the reception quality of at least one of the plurality of signals transmitted from the transmission side, when the reception quality has dropped below a predetermined level, by the quality compensation means, The signal of the channel whose reception quality has deteriorated is reproduced based on other transmitted sound signals. According to such an invention, when the reception quality of an arbitrary transmission signal deteriorates, the transmission signal is reproduced based on another transmission signal having a correlation with the transmission signal. Therefore, even if a burst error that cannot be corrected by, for example, an error correction code occurs in an arbitrary transmission signal, it can be reliably reproduced based on another sound reception signal. Further, since reproduction is performed based on a signal of a channel having strong correlation such as a stereo signal, for example, accurate reproduction can be performed as compared with a case where estimation is performed based on a signal of a past frame.

The above-mentioned quality compensating means includes, when it is detected that the reception quality of the signal to be monitored has dropped below a predetermined level, the signal of the monitoring target whose reception quality has dropped is replaced by another transmitted sound signal. What replaces the signal, the correlation between a plurality of transmitted signals is extracted, and when it is detected that the reception quality of the signal to be monitored has dropped below a predetermined level, the signal whose reception quality has dropped is A signal that is reproduced based on another transmitted sound signal and the extracted value of the correlation may be considered.

The former has an advantage that it can be realized by a very simple circuit configuration and control because it is only necessary to switch signals between channels. In the latter, signal reproduction is performed in consideration of a correlation between a signal to be reproduced and another signal, so that more accurate signal reproduction can be performed.

Further, according to the present invention, a plurality of transmission signals having a correlation with each other are mutually operated to generate a plurality of operation information,
The present invention can also be applied to a system that transmits such calculation information in parallel. That is, a plurality of first received signals corresponding to a plurality of transmission signals are reproduced by performing an inverse operation on the plurality of transmitted operation information, and the transmitted information and the reproduced plurality of first reception signals are compared with each other. And a plurality of second reception signals corresponding to a plurality of transmission signals are estimated based on the correlation and the information. Then, the reception quality of the transmitted information is monitored, and as a result of the monitoring, when the reception quality of the difference information is equal to or higher than a predetermined level, the first quality is monitored.
Is selected and output, and when the reception quality of the difference information is lower than a predetermined level, the second reception signal is selected and output.

Further, the present invention transmits a plurality of signals from a transmitting side to a receiving side, and transmits correlation information between these signals. It is also characterized in that a signal whose reception quality has deteriorated is reproduced based on the other received signals that can be received and the correlation information.

With such a configuration, since correlation information between a plurality of signals is extracted on the transmission side and notified to the reception side, almost no arbitrary signal can be received due to a burst error or the like. , It is possible to accurately reproduce the above-mentioned unreceivable signal.

On the other hand, another invention is such that in a system for transmitting a plurality of signals having a correlation with each other from a transmitting side to a receiving side, transmission timings of the respective signals are made different from each other by a predetermined time on the transmitting side. Then, the reception side monitors the reception quality of each of the plurality of signals transmitted from the transmission side, and when it is detected that the reception quality of any signal has dropped below a predetermined level, the reception of the signal The low-quality section is reproduced based on a corresponding section of another signal arriving with the time difference of the predetermined time.

According to the present invention, since a plurality of signals are transmitted with a time difference from each other, even if a burst error occurs simultaneously in these plurality of channels due to, for example, fading or the like, the received signal of one channel is converted to the other channel. Can be reproduced on the basis of a sound received signal.

At this time, a correlation between a plurality of signals may be obtained on the receiving side, and an unreceivable signal may be reproduced based on the signal that has been successfully received and the correlation. Further, on the transmitting side, correlation information between a plurality of signals is obtained and added to each signal or transmitted independently to the receiving side, and the signal successfully received on the receiving side and the notified correlation information are compared with each other. A signal that cannot be received may be reproduced based on the signal. This enables more accurate signal reproduction.

Still another aspect of the present invention is a digital signal transmission system for transmitting a plurality of signals having correlation with each other from a transmitting side to a receiving side. After the time stamp information is added to each transmission, the transmission timings are different from each other by a predetermined time and then transmitted. On the other hand, on the receiving side, time stamp information is extracted from each of the plurality of signals transmitted from the transmitting side, and a time difference between the plurality of transmitted signals is detected based on the extracted time stamp information, Based on the detected time difference, the time difference between the plurality of signals provided on the transmission side is eliminated. Then, for each of the plurality of signals, the reception quality is monitored, and when it is detected that the reception quality of an arbitrary signal has dropped below a predetermined level, the reception quality reduction section of the signal is set to the other signal. The reproduction is performed based on the temporally corresponding section before the time difference is formed.

According to the present invention, a plurality of signals to be transmitted are transmitted with a predetermined transmission time difference after time stamp information is added on the transmission side. For this reason, the receiving side detects the transmission time difference between the signals based on the time stamp information attached to each signal, and based on the detected time difference, restores each signal to the original state before giving the time difference. You can go back.

Therefore, there is no need to set the time difference information in the receiving side device in advance, or to notify the time difference information from the transmitting side to the receiving side. Therefore, there is an advantage that the initial setting of a large number of receiving-side devices can be simplified, and that it is possible to easily cope with a case where it is necessary to change a transmission time difference between signals. Further, for example, even if the time difference given between a plurality of signals at the time of demultiplexing changes, it is possible to absorb the change in the time difference and always accurately synchronize the signals.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention relates to a digital stereo broadcast system which encodes two-channel digital stereo signals and transmits the signals via different channels. In the signal transmission device on the side, error detection is performed for each of the received signals of the two channels, and when an error of a predetermined amount or more is detected in one of the channels, the signal is correctly received instead of the stereo signal of the channel. This is to output a stereo signal of another channel.

FIG. 1 is a circuit block diagram showing a main part of a digital stereo transmission system according to the first embodiment. Reference numeral 10 denotes a transmission side signal transmission device, and reference numeral 20 denotes a reception side signal transmission device. Is shown.

First, the signal transmitting device 10 on the transmitting side multiplexes audio encoders 11L and 11R provided for the left and right channels R and R of the stereo signal with error detecting code adders 12L and 12R. And a unit 13.

The audio encoders 11L and 11R encode the input audio signals ASLin and ASRin divided into a predetermined frame length by a frame dividing unit (not shown) for each frame. As an encoding method, for example, an MPEG / Audio algorithm is used. The details are described in Hiroshi Yasuda, "International Standard for MPEG / Multimedia Coding".

The error detection code adders 12L and 12R add an error detection code for detecting a transmission error to each frame of the encoded signal output from the audio encoders 11L and 11R.

The multiplexing unit 13 includes the error detection code adder 1
The left channel transmission signal and the right channel transmission signal output from the 2L and 12R are time-division multiplexed in frame units, and the multiplexed transmission signal is supplied to a radio modulation unit (not shown).

On the other hand, the signal transmitting device 20 on the receiving side includes a separating unit 21, error detectors 22L and 22R, audio decoders 23L and 23R, and signal selection switches 24L and 24R.
And

The separation unit 21 separates the multiplexed reception signal received and demodulated by a radio demodulation unit (not shown) into a left channel reception signal and a right channel reception signal in frame units. The signal and the received signal of the right channel are input to error detectors 22L and 22R, respectively.

The error detectors 22L and 22R detect the presence or absence of a code error using an error detection code added to the left channel received signal and the right channel received signal.
Then, a switching control signal corresponding to the detection result is provided to the signal selection switches 24L and 24R.

The audio decoders 23L and 23R decode the left channel received signal and the right channel received signal output from the error detectors 22L and 22R, and output decoded frame signals.

The signal selection switches 24L and 24R operate according to the switching control signals output from the error detectors 22L and 22R, and output the left channel decoded frame signals and the right channel decoded frame signals output from the audio decoders 23L and 23R. The decoder selectively selects and outputs a decoded frame signal.

Next, the operation of the system configured as described above will be described. In the signal transmission device 10 on the transmission side,
Input audio signals ASLin and ASRin output from left (L) and right (R) microphones (not shown)
First, the signal is converted into a digital signal and divided into frames of a fixed length.
It is encoded for each frame in 1R. Then, the coded signals of both the left and right channels are time-division multiplexed by the multiplexing unit 13 after an error detection code is added to each frame by the error detection code adders 12L and 12R. Then, after being digitally modulated by a radio modulation unit (not shown), the frequency is converted to a radio carrier frequency, further amplified to a predetermined transmission power, and transmitted from an antenna.

On the other hand, in the signal transmission device 20 on the reception side, the radio transmission signal transmitted from the signal transmission device 10 on the transmission side is received by the antenna and then demodulated by a radio demodulation unit (not shown). Each frame is separated into a left channel received signal and a right channel received signal. The left channel received signal and the right channel received signal are decoded by the audio decoders 23L and 23R after the presence or absence of a code error is detected for each frame by the error detectors 22L and 22R. Then, these decoded frame signals are sent to the signal selection switches 24L, 24L.
The signal is supplied to a signal reproducing circuit (not shown) via R.

Now, it is assumed that the quality of the radio transmission path is good and no code error has occurred in the received signals of both the left and right channels. In this case, no error is detected by the error detectors 22L, 22R, and therefore, the signal selection switches 24L,
24R selects the output signals of the audio decoders 23L and 23R, respectively. Therefore, in this case, the signals output from the audio decoders 23L and 23R are directly used as the left-channel decoded frame signal ASLout.
It is output as the decoded frame signal ASRout of the right channel.

On the other hand, it is now assumed that fading or the like has occurred on the radio transmission path, and the right channel signal has not been correctly transmitted in an arbitrary frame transmission section due to the influence. In this case, in the signal transmission device 20 on the receiving side, the error detector 22R for the right channel detects a code error in an arbitrary frame of the received signal of the right channel. Then, a switching control signal is output from the error detector 22R to the signal selection switch 24R, whereby the signal selection switch 24R switches from the audio decoder 23R to the audio decoder 23L during the frame in which the error is detected. . Accordingly, in this case, the left-channel decoded frame signal ASLout output from the audio decoder 23L is output to the next-stage signal reproducing circuit (not shown) in both the left and right channels.

That is, for the left channel (L), the decoded frame signal of the audio decoder 23L is output as it is, but for the right channel (R), the output signal of the audio decoder 23R is used instead of the output signal of the audio decoder 23R. The decoded frame signal of the audio decoder 23L is output.

As described above, in the first embodiment of the present invention, in the signal transmission device 20 on the receiving side, the error detector 2
At 2L and 22R, the presence / absence of a code error in the received signal of the left channel and the received signal of the right channel is determined. If a code error is detected in one channel (for example, the right channel (R)) in an arbitrary transmission frame, Outputs a switching control signal from the error detector 22R, and switches the signal selection switch 24R on the side where an error is detected to the side for selecting a decoded frame signal on the other channel side.

Therefore, when a code error is detected in the decoded frame signal of one channel, the decoded frame signal in which the code error has occurred is included in the decoded frame signal of the other channel in the same transmission frame normally received. Be replaced. For this reason, even if the decoded frame signal of one channel cannot be correctly received, the decoded frame signal of the other channel is reproduced instead, so that the reception quality of both channels does not extremely deteriorate, and Stereo reception with less unnaturalness can be maintained by the correlation between channels.

(Second Embodiment) A second embodiment of the present invention relates to a receiving-side signal transmission device used in a digital stereo transmission system, in which a left-channel decoded frame signal and a right-channel decoded frame signal are transmitted. Is extracted, and if a code error is detected in the received signal of one channel, the code error is detected based on the correctly received decoded frame signal of the other channel and the correlation value. It estimates the decoded frame signal of the estimated channel and outputs the estimated decoded frame signal.

FIG. 2 is a circuit block diagram showing a configuration of a signal transmission device on the receiving side according to the second embodiment.
In this figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description is omitted.

The signal transmission device 20 'of this embodiment includes:
A correlation extractor 25 and another signal estimator 26 are provided. The correlation extractor 25 extracts a frame-by-frame correlation between the left channel decoded frame signal output from the audio decoder 23L and the right channel decoded frame signal output from the audio decoder 23R. As a method for extracting the correlation, for example, a learning type algorithm using an adaptive filter is used, and a correlation between the signals of both channels is extracted using the decoded frame signal of the left channel as a teacher signal and the decoded frame signal of the right channel as a reference signal. Is used.

The other signal estimator 26 estimates the right channel decoded frame signal based on the left channel decoded frame signal output from the audio decoder 23L and the correlation information extracted by the correlation extractor 25. With
A left channel decoded frame signal is estimated based on the right channel decoded frame signal output from the audio decoder 23R and the correlation information extracted by the correlation extractor 25.

More specifically, for example, when estimating the signal of the left channel, an adaptive filter which has been learned in advance by the correlation extractor 25 is applied to the signal of the right channel. Further, when estimating the right channel signal, it can be realized by applying an inverse filter of the adaptive filter, which has been learned in advance by the correlation extractor 25, to the left channel signal.

The signal selection switches 24L and 24R are estimated by the other signal estimator 26 and the decoded frame signals output from the audio decoders 23L and 23R in accordance with the switching control signals generated by the error detectors 22L and 22R. And selectively outputs the decoded frame signal.

With such a configuration, when the quality of the radio transmission path is good and no code error occurs in the received signals of both the left and right channels, no error is detected by the error detectors 22L and 22R. Therefore, the signal selection switch 24
L and 24R are audio decoders 23L and 23R, respectively.
Select the output signal of Therefore, in this case, the decoded frame signals output from the audio decoders 23L and 23R are directly converted into the left channel decoded frame signal ASLout and the right channel decoded frame signal ASR.
Output as out.

On the other hand, it is assumed that fading or the like occurs on the wireless transmission path, and the signal of the right channel is not correctly transmitted in an arbitrary frame transmission section due to the influence. In this case, in the signal transmission device 20 'on the receiving side, the error detector 22R for the right channel detects a code error in an arbitrary frame of the received signal of the right channel. Then, from the error detector 22R, the signal selection switch 2
A switching control signal is output to 4R, whereby the signal selection switch 24R switches from the audio decoder 23R to the other signal estimator 26 during the frame in which the error is detected.

Accordingly, in this case, the left-channel decoded frame signal output from the audio decoder 23L is directly output as ASLout to the next-stage signal reproducing circuit (not shown), but a code error is detected. In the other right channel, instead of the right channel decoded frame signal output from the audio decoder 23R, the other signal estimator 26 calculates a normal left channel decoded frame signal and correlation information between the left and right channels. Is supplied as ASRout.

That is, even if a signal of one channel cannot be correctly reproduced in an arbitrary transmission frame due to a burst error or the like, the signal of this channel is correctly transmitted to the decoded frame signal of the other channel between the left and right channels. , And is accurately replaced based on the estimated decoded frame signal.

Therefore, as in the first embodiment, no extreme deterioration in reception quality occurs in both channels. Moreover, by estimating the signal of the channel that could not be received correctly using the correlation information between both channels,
Even when the correlation between the signals between the two channels is weak, the power, phase difference, and the like are more accurately compensated, whereby a high-quality stereo signal can be reproduced without impairing the natural feeling.

(Third Embodiment) In a third embodiment of the present invention, common information (main signal) and difference information (sub signal) between a left channel signal and a right channel signal are used as a stereo transmission system. ) Are generated, and these signals are multiplexed on separate channels and transmitted. The error compensation system of the present invention is applied to this system. As a method for generating common information and difference information between the left and right channels, for example, an intensity method or an MS method defined by a stereo method of the MPEG1 / Audio algorithm is used.

FIG. 3 is a circuit block diagram showing the configuration of a digital stereo transmission system according to the third embodiment. Reference numeral 30 denotes a transmission-side signal transmission device, and reference numeral 40 denotes a reception-side signal transmission device. I have.

The signal transmission device 30 on the transmitting side includes an adder 31
M, a subtractor 31S, and a main signal encoder 32M
, A sub-signal encoder 32S, and an error correction code adder 3
3M, an error detection code adder 33S, and a multiplexing unit 34.

The adder 31M and the subtractor 31S are connected to the MS
It generates information and difference information common to both the left and right channels according to the method.
For each frame of Lin and ASRin, both signals A
The sum signal of SLin and ASRin is output as a main signal, and the difference signal is output as a sub signal. In the main signal and the sub signal, a large number of bits are allocated to the main signal.

The main signal encoder 32M encodes the main signal output from the adder 31M. The sub-signal encoder 32S encodes the sub-signal output from the subtractor 31S. As a coding method, for example, a method using an MPEG / Audio algorithm is used.

The error correction code adder 33M adds a code for detecting and correcting a transmission error, such as a Reed-Solomon code or a convolutional code, to the coded main signal. The error detection code adder 33S adds an error detection code, such as a parity bit, for detecting a transmission error to the coded sub-signal.

The multiplexing unit 34 includes the error correction code adding unit 3
The coded main signal and the coded sub-signal output from the 3M and error detection code adder 33S are time-division multiplexed in frame units, and the multiplexed transmission signal is supplied to a radio modulation unit (not shown).

On the other hand, the signal transmission device 40 on the receiving side includes a demultiplexer 41, an error corrector 42M, an error detector 42S, a main signal decoder 43M, a sub signal decoder 43S,
Correlation extractor 44L, R correlation extractor 44R, L signal estimator 45L, R signal estimator 45R, and subtractor 46M
, An adder 46S, and signal selection switches 47L and 47R.
And

The separation unit 41 separates the multiplexed reception signal received and demodulated by a radio demodulation unit (not shown) into a main signal as common information and a sub-signal as difference information in frame units. And the sub-signal are input to an error corrector 42M and an error detector 42S, respectively.

The error corrector 42M performs error correction decoding on the received main signal for each frame, and supplies the received main signal after error correction to the main decoder 43M. The error detector 42S determines the presence or absence of a transmission error for each frame of the received sub-signal, and supplies the received sub-signal to the sub-signal decoder 43S.

The main signal decoder 43M includes an error correction unit 4M.
The received main signal output from 2M is decoded, and the decoded main signal is input to the subtractor 46M and the adder 46S. The sub signal decoder 43S decodes the received sub signal output from the error detector 42S, and inputs the decoded sub signal to the adder 46S and the subtractor 46M.

The subtractor 46M subtracts the decoded sub-signal from the decoded main signal, and outputs the difference output as a left-channel reproduction signal. The adder 46S adds the decoded main signal to the decoded sub-signal, and outputs the added output as a right-channel reproduction signal.

The L correlation extractor 44L extracts the correlation between the decoded main signal output from the main signal decoder 43M and the left channel reproduced signal output from the subtractor 46M. The R correlation extractor 44R extracts the correlation between the decoded main signal output from the main signal decoder 43M and the right channel reproduced signal output from the adder 46S.

The L signal estimator 45L estimates the reproduced signal of the left channel based on the decoded main signal output from the main signal decoder 43M and the correlation extracted by the L correlation extractor 44L. The R signal estimator 45R estimates the right channel reproduced signal based on the decoded main signal output from the main signal decoder 43M and the correlation extracted by the R correlation extractor 44R.

The signal selection switches 47L and 47R operate in accordance with the switching control signal output from the error detector 42S. During a frame period in which no code error is detected in the received sub-signal, the signal selection switches 47L and 47R are switched.
7R selects and outputs the left channel reproduced signal and the right channel reproduced signal obtained by the subtractor 46M and the adder 46S, respectively. On the other hand, during the frame period in which a code error is detected in the received sub-signal, the signal selection switches 47L, 47L
7R selects and outputs the left channel reproduction signal and the right channel reproduction signal respectively estimated by the L signal estimator 45L and the R signal estimator 45R.

Next, the operation of the system configured as described above will be described. In the signal transmission device 30 on the transmission side,
Input audio signals ASLin and ASRin output from left (L) and right (R) microphones (not shown)
First, it is converted into a digital signal and divided into frames of a fixed length. Then, the adder 31M and the subtractor 31S
And is divided into a main signal, which is common information between the left and right channels, and a sub-signal, which is difference information.
The main signal and the sub-signal are encoded for each frame by the main signal encoder 32M and the sub-signal encoder 32S, respectively, and then the error correction code adder 33 is added.
An error correction code and an error detection code are added to each frame by the M and error detection code adder 33S, and then the signal is time-division multiplexed by the multiplexing unit 34. The time-division multiplexed signal is digitally modulated by a radio modulation unit (not shown), frequency-converted to a radio carrier frequency, amplified to a predetermined transmission power, and transmitted from an antenna.

On the other hand, in the signal transmission device 40 on the reception side, the radio transmission signal transmitted from the signal transmission device 10 on the transmission side is received by an antenna and then demodulated by a radio demodulation unit (not shown). The received signal is separated into a received main signal and a received sub signal for each frame. The received main signal is subjected to an error correction decoding process in an error corrector 42M to correct a transmission error, and then the main signal decoder 43M
Is decrypted. On the other hand, the received sub-signal is
After the presence or absence of a code error is determined by the sub-signal decoder 4
Decoded in 3S.

Then, the difference between the decoded main signal and the decoded sub signal is obtained by the subtractor 46M, and this difference signal is output as a left channel signal. Further, a sum signal of the decoded main signal and the decoded sub signal is obtained by the adder 46S, and this sum signal is output as a right channel signal.

At this time, the L correlation extractors 44L and R
The correlation extractor 44R prepares a correlation between the decoded main signal and the right channel signal output from the adder 46S and a left main signal output from the subtractor 46M in preparation for occurrence of a transmission error. The correlation with the channel signal is extracted. Then, the L signal estimators 45L and R
In the signal estimator 45R, the left channel signal and the right channel signal are estimated by reflecting the extracted correlation value on the decoded main signal, respectively.

By the way, when the quality of the radio transmission path is good and no code error occurs in the received sub-signal, no error is detected by the error detector 42S. 46M and the adder 46S are selected. Therefore, in this case, a signal having a half of the difference between the main signal and the sub-signal output from the subtractor 46M is the decoded frame signal AS of the left channel.
The signal is selected and output as Lout, and a signal of 和 of the sum of the main signal and the sub-signal output from the adder 46S is selectively output as the right channel decoded frame signal ASRout.

On the other hand, it is assumed that fading or the like occurs on the radio transmission path, and the main signal and the sub-signal are not correctly transmitted in an arbitrary frame transmission section due to the influence. In this case, the code error occurring in the received main signal is corrected by the error corrector 42M, but the code error of the sub-signal is not corrected and the error detector 42S detects that there is a code error.

For this reason, the signal selection switches 47L, 47
R is switched to the L signal estimator 45L and the R signal estimator 45R, and as a result, the signals output from the subtractor 46M and the adder 46S are estimated by the L signal estimator 45L and the R signal estimator 45R. The left channel signal and the right channel signal are selectively output. That is, instead of the output signals of the subtractor 46M and the adder 46S containing the code error, the L correlation value and R
The left channel signal and the right channel signal estimated by reflecting the correlation value are selected.

As described above, when an error occurs in the sub signal, since both the left channel signal and the right channel signal are estimated from the main signal and the previously extracted correlation, error compensation is performed. The difference between the channel signal and the right channel signal is more accurately compensated, so that a stereo audio signal having a natural feeling as well as a low noise can be reproduced.

(Fourth Embodiment) In a fourth embodiment of the present invention, in a digital stereo transmission system, in a signal transmission device on the transmitting side, a correlation between a right channel signal with respect to a left channel signal and a left channel with respect to a right channel signal are obtained. After extracting the correlations of the signals and encoding the correlation information, the correlation information is added to the encoded left channel signal and right channel signal and transmitted to the receiving side through different channels. Then, when a code error is detected in the signal of the left channel or the right channel in the signal transmission device on the receiving side, the right channel is extracted from the received signal of the left channel or the right channel and the correlation information added to the signal. Alternatively, a left channel signal is estimated, and the estimated signal is output instead of the signal in which the error is detected.

FIG. 4 is a circuit block diagram showing the configuration of a digital stereo transmission system according to the fourth embodiment. Reference numeral 50 denotes a transmission-side signal transmission device, and 60 denotes a reception-side signal transmission device. I have.

The signal transmission device 50 on the transmitting side includes audio encoders 51L and 51R for encoding the left channel signal ASLin and the right channel signal ASRin, respectively, an R correlation extractor 52L, an L correlation extractor 52R, Chemistry 53
L, 53R, error detection code adders 54L, 54R,
A multiplexing unit 55.

The R correlation extractor 52L extracts the correlation between the left channel signal ASLin and the right channel signal ASRin. For example, the R correlation extractor 52L employs an adaptive filter using the right channel signal ASRin as a teacher signal and the left channel signal ASLin as a reference signal. The learning type algorithm used is used.

The L correlation extractor 52R outputs the left channel signal A
The correlation of the right channel signal ASRin with respect to SLin is extracted. For example, the left channel signal ASLin is extracted as a teacher signal,
A learning type algorithm using an adaptive filter using the right channel signal ASRin as a reference signal is used.

The audio encoders 51L and 51R respectively include a left channel signal ASLin and a right channel signal ASR
Performs encoding of in. As the encoding method, for example, M
The PEG / Audio algorithm is used.

On the other hand, the encoders 53L and 53R
The correlation information output from the correlation extractor 52L and the L correlation extractor 52R is encoded. As the encoding method,
For example, a method is used in which a filter table of the adaptive filter is vector-quantized to create a code table thereof, and encoding is performed using the code table.

The error detection code adders 54L and 54R respectively provide the left channel and right channel encoded signals (main signals) output from the audio encoders 51L and 51R.
And the R output from the encoders 53L and 53R, respectively.
Correlation information and L correlation information (side signal) are added, and an error detection code is added to each frame of these signal sequences.

The multiplexing unit 55 includes the error detection code adding unit 5
Each signal sequence output from the 4L and 54R is time-division multiplexed into different channels in frame units. The time-division multiplexed signal is modulated by a radio modulator (not shown), converted to a predetermined radio frequency, amplified to a predetermined transmission power, and transmitted from an antenna.

On the other hand, the signal transmitting device on the receiving side
, Error detectors 62L and 62R, and audio decoder 6
3L, 63R, signal selection switches 64L, 64R,
An R correlation decoder 65L, an L correlation decoder 65R, an R signal estimator 66L, and an L signal estimator 66R are provided.

The separation unit 61 separates the multiplexed reception signal received and demodulated by a radio demodulation unit (not shown) into a left channel reception signal and a right channel reception signal in frame units. The signal and the received signal of the right channel are input to error detectors 62L and 62R, respectively.

The error detectors 62L and 62R detect the presence or absence of a code error using the error detection code added to the left channel received signal and the right channel received signal.
Then, a switching control signal corresponding to the detection result is provided to the signal selection switches 64L and 64R.

The audio decoders 63L and 63R decode the main signal of the left channel received signal and the right channel received signal output from the error detectors 62L and 62R, respectively. Output a signal.

R correlation decoder 65L and L correlation decoder 65
R decodes the side signal of the left channel received signal and the right channel received signal output from the error detectors 62L and 62R, that is, the R correlation information and the L correlation information.

R signal estimator 66L and L signal estimator 66
R is the left and right channel decoded signals output from the audio decoders 63L and 63R, respectively, and the R and L correlation information decoded by the R and L correlation decoders 65L and 65R, respectively. , The right channel main signal and the left channel main signal are estimated.

The signal selection switches 64L and 64R operate in accordance with the switching control signals output from the error detectors 62L and 62R, respectively, and operate in response to the audio decoders 63L and 64R.
Alternatively, the left channel decoded signal and the right channel decoded signal output from 63R and the left channel main signal and the right channel main signal estimated by the R signal estimator 66L and the L signal estimator 66R are selected. Select and output.

Next, the operation of the system configured as described above will be described. In the signal transmission device 50 on the transmission side,
Input audio signals ASLin and ASRin output from left (L) and right (R) microphones (not shown)
First, the signal is converted into a digital signal and divided into frames of a fixed length.
It is encoded frame by frame in R.

At this time, the R correlation extractor 52L extracts the correlation of the left channel input audio signal ASLin with the right channel input audio signal ASRin,
The L correlation extractor 52R extracts the correlation between the input audio signal ASRin of the right channel and the input audio signal ASRin of the left channel. Then, the extracted R correlation information and L correlation information are coded by the encoder 53L,
After being encoded by 53R, they are added as side signals to the encoded signal of the left channel and the encoded signal of the right channel, respectively.

The coded signal of the left channel and the coded signal of the right channel to which the side signal is added are added with error detection codes for each frame by error detection code adders 54L and 54R, and then multiplexed. The signal is time-division multiplexed at 55, and then digitally modulated by a wireless modulator (not shown), frequency-converted to a wireless carrier frequency, further amplified to a predetermined transmission power, and transmitted from an antenna.

On the other hand, in the signal transmission device 60 on the reception side, the radio transmission signal transmitted from the signal transmission device 50 on the transmission side is received by the antenna and then demodulated by a radio demodulation unit (not shown). Each frame is separated into a left channel received signal and a right channel received signal. From the left channel received signal and the right channel received signal, the presence or absence of a code error is detected for each frame by the error detectors 62L and 62R, and then the main signal is decoded by the audio decoders 63L and 63R.

If the quality of the radio transmission path is good and there is no code error in the received signals of the left and right channels, no error is detected by the error detectors 62L and 62R. The output signals output from the audio decoders 63L and 63R are selected. Therefore, in this case, the left channel decoded signal and the right channel decoded signal output from the audio decoders 63L and 63R are supplied to a signal reproducing circuit (not shown) as they are, and are reproduced as audio signals of left and right channels.

On the other hand, it is now assumed that fading or the like has occurred on the radio transmission path, and the signal of the right channel has not been correctly transmitted in an arbitrary frame transmission section due to the influence. In this case, the R-correlation information added as side information to the left-channel received signal is decoded by the R-correlation decoder 65L, and the R-correlation information and the decoded error-free left-channel decoded signal are used. R signal estimator 6
In 6L, the decoded signal of the right channel is estimated. Then, the estimated right channel decoded signal is selected by the signal selection switch 64R, supplied to a signal reproducing circuit (not shown), and reproduced as a right channel audio signal.

Since no code error has occurred in the left channel, the decoded signal of the left channel output from the audio decoder 63L is switched to the signal selection switch 64L.
Is supplied to the signal reproduction circuit as it is, and reproduced as an audio signal of the left channel.

Similarly, when a transmission error occurs in an arbitrary frame of the received signal of the left channel, the L correlation information added to the received signal of the right channel is converted to the L correlation decoder 65.
It is decoded by R, and the decoded signal of the left channel is estimated from the decoded L correlation information and the decoded signal of the right channel.
Then, the estimated left-channel decoded signal is selected by the signal selection switch 64L, supplied to a signal reproducing circuit (not shown), and reproduced as a left-channel audio signal.

Note that, for the right channel, since no code error has occurred in the received signal, the audio decoder 63
The decoded signal of the right channel output from R is directly supplied to the signal reproduction circuit via the signal selection switch 64R,
Reproduced to the right channel audio signal.

As described above, in the fourth embodiment, the correlation between the signals of the left and right channels is extracted on the transmitting side, and the correlation information is added to the left and right main signals as side signals and transmitted, and the reception is performed. If a code error is detected in one of the left and right channels on the side, a decoded signal is estimated from the decoded signal of the correctly received channel and the correlation information transmitted together with this signal, and this estimation is performed. The decoded signal is used for signal reproduction instead of the decoded signal in which the code error is detected.

Therefore, the decoded signal can always be estimated by using accurate correlation information, as compared with the case where the signal transmission device 60 on the receiving side extracts the correlation between the left and right channels based on the received signal. . Therefore, more accurate error compensation can be performed, and thereby a high-quality audio signal can be reproduced.

(Fifth Embodiment) The fifth embodiment according to the present invention
The embodiment of the present invention, by delaying one of the signals of the left and right channels in each of the signal transmission device on the transmission side and the reception side, the transmission timing on the wireless transmission path of the signal frames of the left and right channels corresponding to each other temporally, The difference is made at least by a time corresponding to the maximum time length of the burst error.

FIG. 5 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to the fifth embodiment. In this figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description is omitted.

In the figure, the signal transmitting device 10 on the transmitting side
A delay unit 14 is interposed between the left channel error detection code adder 12L at 0 and the multiplexing unit 13. The delay unit 14 delays the transmission signal of the left channel output from the error detection code adder 12L by a predetermined time.
This delay time is set to the maximum time of a burst error assumed on the wireless transmission path.

On the other hand, a delay unit 27 is interposed between the demultiplexing unit 21 and the right channel error detector 22R in the signal transmission device 200 on the receiving side. This delay device 27
The right channel reception signal output from the separation unit 21 is delayed by a predetermined time. This delay time is set to the same time as the time set in the delay unit 14 provided in the signal transmission device 100 on the transmission side, that is, the maximum time of a burst error assumed on the wireless transmission path.

With such a configuration, the audio signals ASLin and ASRin output from the left (L) and right (R) microphones (not shown) are first converted into digital signals in the signal transmission device 100 on the transmission side. At the same time, the audio data is divided into frames of a fixed length, and subsequently encoded by the audio encoders 11L and 11R for each frame. The coded signals of the left and right channels are each added with an error detection code for each frame by error detection code adders 12L and 12R, and the transmission signal of the left channel is transmitted to the delay unit 14 on the radio transmission path. After the maximum time delay of the burst error assumed in (1), the multiplexing unit 13 performs time division multiplexing with frame synchronization.

That is, on the time-division multiplexed signal, the transmission signal frame of the left channel and the transmission signal frame of the right channel are arranged with a time difference equal to or longer than the maximum time length of the burst error assumed on the radio transmission path. FIG. 6 (a)
Shows an example of the signal format of the time division multiplexed signal after the time difference is formed. FIG.
(B) shows a signal format when no time difference is formed.

On the other hand, in the signal transmission device 200 on the reception side, the radio transmission signal transmitted from the signal transmission device 100 on the transmission side is received by the antenna and then demodulated by a radio demodulation unit (not shown). Each frame is separated into a left channel received signal and a right channel received signal. The reception signal of the right channel is delayed by a time corresponding to the maximum time length of the burst error assumed by the delay unit 27, and after the frame synchronization with the reception signal of the left channel is established, the error Detector 22L,
Input to 22R. Then, the error detector 22L,
At 22R, the presence or absence of a code error is detected for each frame, and then decoded by the audio decoders 23L and 23R.

Now, it is assumed that the quality of the radio transmission path is good and no code error has occurred in the received signals of both the left and right channels. In this case, no error is detected by the error detectors 22L, 22R, and therefore, the signal selection switches 24L,
24R selects the output signals of the audio decoders 23L and 23R, respectively. Therefore, in this case, the signals output from the audio decoders 23L and 23R are directly used as the left-channel decoded frame signal ASLout.
It is output as the decoded frame signal ASRout of the right channel.

On the other hand, it is now assumed that fading or the like has occurred on the radio transmission path, and the signal of both the left and right channels has caused a burst error simultaneously in an arbitrary transmission frame section due to the influence. However, the transmission signals of both the left and right channels are multiplexed after being shifted in advance by the maximum time of the burst error in the signal transmission device 100 on the transmission side. For this reason, as described above, even if the signal frames of the left and right channels simultaneously cause a burst error in an arbitrary transmission frame section, the signal frames of the right and left channels that are originally temporally corresponding to these left and right channels are Is transmitted in another transmission frame section, there is a high possibility that it will be correctly received without being affected by the burst error.

Therefore, the signal transmission device 200 on the receiving side
In the above, after the time difference between the left and right channels is eliminated by the delay unit 27, error detection is performed, and signal selection of the left and right channels is performed by the signal selection switches 24L and 24R in accordance with the result, so that the channel in which the burst error has occurred is determined. The signal can be replaced with a signal of the other channel having a strong correlation corresponding to the signal in time. For this reason,
Even if both left and right channel signals multiplexed and transmitted on the same transmission frame on the wireless transmission path cause a burst error, both left and right channel signals can be reproduced.

(Sixth Embodiment) The sixth embodiment according to the present invention
In the embodiment of the present invention, the transmission timing of the signal frames of the left and right channels corresponding to each other on the radio transmission path is made different at least by the time corresponding to the time length of the burst error. Extracting the correlation of the signal between both channels, and if a code error is detected in the received signal of one channel, the code error is detected based on the correctly received decoded frame signal of the other channel and the correlation value. Is used to estimate the decoded frame signal of the detected channel.

FIG. 7 is a circuit block diagram showing the main configuration of a digital stereo transmission system according to the sixth embodiment. 2 and 5, the same parts as those in FIG. 2 and FIG.

In FIG. 7, the signal transmitting device 10 on the transmitting side
A delay unit 14 is interposed between the multiplexing unit 13 and the error detection code adder 12L for the left channel at 0 as in the fifth embodiment. The delay unit 14 delays the transmission signal of the left channel output from the error detection code adder 12L by a predetermined time. This delay time is set to the maximum time of a burst error assumed on the wireless transmission path.

On the other hand, a delay unit 27 is also interposed between the demultiplexing unit 21 and the right channel error detector 22R in the signal transmission device 201 on the receiving side. This delay device 27
The right channel reception signal output from the separation unit 21 is delayed by a predetermined time. This delay time is set to the same time as the time set in the delay unit 14 provided in the signal transmission device 100 on the transmission side, that is, the maximum time of a burst error assumed on the radio transmission path.

The signal transmitting device 201 on the receiving side includes:
A correlation extractor 25 and another signal estimator 26 are provided as in the second embodiment. The correlation extractor 25 extracts a frame-by-frame correlation between the left channel decoded frame signal output from the audio decoder 23L and the right channel decoded frame signal output from the audio decoder 23R.

The other signal estimator 26 estimates the right channel decoded frame signal based on the left channel decoded frame signal output from the audio decoder 23L and the correlation information extracted by the correlation extractor 25. With
A left channel decoded frame signal is estimated based on the right channel decoded frame signal output from the audio decoder 23R and the correlation information extracted by the correlation extractor 25.

With such a configuration, in the signal transmission device 100 on the transmission side, the audio signals of each of the left and right channels are encoded by the audio encoders 11L and 11R, and further encoded by the error detection code adders 12L and 12R. After the error detection code is added, one of the left channel signals is delayed by the delay unit 14 by the maximum time length of the burst error. The delayed left channel signal and the undelayed right channel signal are frame-synchronized with each other, and then time-division multiplexed by the multiplexing unit 13 and transmitted.

On the other hand, in the signal transmitting apparatus 201 on the receiving side, the received signal of the right channel, out of the received signal of the left channel and the received signal of the right channel, separated for each frame by the separating unit 21, The signal is delayed by a time corresponding to the maximum time length of the error, and after being synchronized with the received signal of the left channel, is input to the error detectors 22L and 22R. After the error detectors 22L and 22R detect the presence or absence of a code error for each frame, the audio decoders 23L and 22R
Decoded by 3R.

Then, if fading or the like occurs on the radio transmission path and the signals of both the left and right channels are not correctly transmitted due to a burst error in an arbitrary transmission frame section due to the influence, the signal transmission apparatus 201 on the receiving side The right channel error detector 22R detects a code error in an arbitrary frame of the received signal of the right channel. Then, a switching control signal is output from the error detector 22R to the signal selection switch 24R,
As a result, the signal selection switch 24R sets the audio decoder 23R during the frame in which the error is detected.
The side is switched to the other signal estimator 26 side.

Therefore, in this case, the left-channel decoded frame signal output from the audio decoder 23L is directly output as ASLout to the next-stage signal reproducing circuit (not shown), but a code error is detected. In the other right channel, instead of the right channel decoded frame signal output from the audio decoder 23R, the other signal estimator 26 calculates a normal left channel decoded frame signal and correlation information between the left and right channels. Is supplied as ASRout.

In other words, even if a burst error occurs in both the left and right channel signals in an arbitrary transmission frame section of the time division multiplexed signal, the right and left channel signals corresponding to these channel signals in time correspond to each other. Since a transmission time difference is given in advance on the transmission side between the two, there is a high possibility that correct reception can be performed without generating a burst error. Therefore, even if a burst error occurs in the signal of one channel, it is possible to reproduce the signal by compensating for the error based on the signal of the other channel that originally corresponds in time.

Moreover, the reproduction of the signal of the channel on the side where the burst error has occurred is estimated based on the signal of the other channel correctly received and the correlation information between the left and right channels extracted by the correlation extractor 25. As compared with the case where the signals of the left and right channels are simply replaced, even when the correlation between the signals of the two channels is weak, the power and the phase difference are more accurately compensated, so that the natural feeling is not impaired. High quality stereo signals can be reproduced.

(Seventh Embodiment) A seventh embodiment according to the present invention will be described.
In the digital stereo transmission system, in a digital stereo transmission system, a signal transmission device on the transmission side extracts a correlation between both left and right channels, adds this correlation information to a left channel signal and a right channel signal, respectively, and transmits the signals on different channels. In addition, at the time of this transmission, the transmission timings of the signals of the left and right channels are made different from each other by a time corresponding to the maximum time of the burst error.

FIG. 8 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to the seventh embodiment. 4, the same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description is omitted.

In the figure, the signal transmission device 50 on the transmission side
A delay unit 56 is interposed between the left channel error detection code adder 54L at 0 and the multiplexing unit 55. The delay unit 56 delays the transmission signal of the left channel output from the error detection code adder 54L by a predetermined time.
This delay time is set to the maximum time of a burst error assumed on the wireless transmission path.

On the other hand, a delay unit 67 is interposed between the separation unit 61 and the right channel error detector 62R in the signal transmission device 600 on the receiving side. This delay device 67
The right channel reception signal output from the separation unit 61 is delayed by a predetermined time. This delay time is set to the same time as the time set in the delay unit 56 provided in the signal transmission device 500 on the transmission side, that is, the maximum time of a burst error assumed on the wireless transmission path.

With such a configuration, input audio signals ASLin and ASRin output from left (L) and right (R) microphones (not shown) are first converted into digital signals in signal transmitting apparatus 500 on the transmitting side. It is converted and divided into frames of a fixed length, and then encoded by the audio encoders 51L and 51R for each frame.

At this time, the R correlation extractor 52L extracts the correlation between the input audio signal ASLin of the left channel and the input audio signal ASLin of the right channel,
The L correlation extractor 52R extracts the correlation between the input audio signal ASRin of the right channel and the input audio signal ASRin of the left channel. Then, the extracted R correlation information and L correlation information are coded by the encoder 53L,
After being encoded by 53R, they are added as side signals to the encoded signal of the left channel and the encoded signal of the right channel, respectively.

The left-channel coded signal and the right-channel coded signal to which the side signal has been added are subjected to an error detection code adder 54L, 54R, respectively, to which an error detection code is added for each frame, and then to a multiplexing unit. The time division multiplexing is performed at 55.

Prior to the multiplexing, the encoded signal of the left channel is delayed by the delay unit 56 by the maximum time of the burst error. For this reason, the coded signal of the left channel and the coded signal of the right channel are arranged on the time-division multiplexed signal at positions that are temporally separated from each other by the maximum time of the burst error assumed on the radio transmission path. Become. FIG.
(A) shows the signal format of the time division multiplexed signal. FIG. 9B shows a signal format when no time difference is formed.

On the other hand, in the signal transmission device 600 on the reception side, the radio transmission signal transmitted from the signal transmission device 500 on the transmission side is received by the antenna and then demodulated by a radio demodulation unit (not shown). Each frame is separated into a left channel received signal and a right channel received signal. The received signal of the right channel is delayed by the delay unit 67 by a time corresponding to the maximum time length of a burst error assumed on the wireless transmission path, and further, the frame synchronization with the received signal of the left channel is established. After that, it is input to the error detectors 62L and 62R. And
After detecting the presence or absence of a code error for each frame in the error detectors 62L and 62R, the main signal is decoded by the audio decoders 63L and 63R.

Now, it is assumed that the quality of the radio transmission path is good and no code error has occurred in the received signals of both the left and right channels. In this case, no error is detected by the error detectors 62L, 62R, and therefore, the signal selection switches 64L, 62L,
64R selects the output signals of the audio decoders 63L and 63R, respectively. Therefore, in this case, the signals output from the audio decoders 63L and 63R are directly used as the left-channel decoded frame signal ASLout.
It is output as the decoded frame signal ASRout of the right channel.

On the other hand, it is now assumed that fading or the like has occurred on the radio transmission path, and the signal of both the left and right channels has caused a burst error simultaneously in an arbitrary transmission frame section due to the effect. However, the transmission signals of both the left and right channels are multiplexed after being shifted by the maximum time of the burst error in advance in the signal transmission device 500 on the transmission side. For this reason, as described above, even if the signal frames of the left and right channels simultaneously cause a burst error in an arbitrary transmission frame section, the signal frames of the right and left channels that are originally temporally corresponding to these left and right channels are Is transmitted in another transmission frame section, there is a high possibility that it will be correctly received without being affected by the burst error.

Therefore, the signal transmitting apparatus 600 on the receiving side
In the above, after the time difference between the left and right channels is eliminated by the delay unit 67, error compensation is performed based on the correctly received signal of the other channel, so that the signal of the channel in which the burst error has occurred can be reproduced. Becomes

Further, in the present embodiment, the correlation information notified from the transmitting side as side information is used for the error compensation. That is, the R-correlation information added as side information to the received signal of the left channel is decoded by the R-correlation decoder 65L, and the R signal is estimated from the decoded R-correlation information and the decoded signal of the left channel without code error. Table 66
L estimates the decoded signal of the right channel. Then, the estimated right channel decoded signal is selected by the signal selection switch 64R, supplied to a signal reproducing circuit (not shown), and reproduced as a right channel audio signal.

Since no code error has occurred in the left channel, the decoded signal of the left channel output from the audio decoder 63L is transmitted to the signal selection switch 64L.
Is supplied to the signal reproduction circuit as it is, and reproduced as an audio signal of the left channel.

Similarly, when a transmission error occurs in an arbitrary frame of the received signal of the left channel, the L correlation information added to the received signal of the right channel is converted to the L correlation decoder 65.
It is decoded by R, and the decoded signal of the left channel is estimated from the decoded L correlation information and the decoded signal of the right channel.
Then, the estimated left-channel decoded signal is selected by the signal selection switch 64L, supplied to a signal reproducing circuit (not shown), and reproduced as a left-channel audio signal.

Note that for the right channel, since no code error has occurred in the received signal, the audio decoder 63
The decoded signal of the right channel output from R is directly supplied to the signal reproduction circuit via the signal selection switch 64R,
Reproduced to the right channel audio signal.

As described above, according to the seventh embodiment, when the transmitting side multiplexes the transmission signals of both the left and right channels and transmits the multiplexed signal, the delay unit 56 sets the maximum burst error assumed on the radio transmission path. By forming the mutual time difference by the time length, there is less concern that the signals of the left and right channels that originally correspond in time may cause a burst error at the same time. The signal can be reproduced more reliably.

Further, in the seventh embodiment, the correlation between the signals of the left and right channels is extracted on the transmitting side, and the correlation information is added to the left and right main signals as side signals and transmitted. When a code error is detected in one of the channels, a decoded signal is estimated from the decoded signal of the channel received correctly and the correlation information transmitted together with the signal, and the estimated decoded signal Is used for signal reproduction in place of the decoded signal in which the code error is detected.

Therefore, compared with the case where the signal transmission apparatus 600 on the receiving side extracts the correlation of the signal between the left and right channels based on the received signal, the decoded signal can always be estimated using accurate correlation information. . Therefore, more accurate error compensation can be performed, and thereby a high-quality audio signal can be reproduced.

(Eighth Embodiment) An eighth embodiment according to the present invention.
In the embodiment of the present invention, in the signal transmission device on the transmission side, after adding time stamp information to the signals of both the left and right channels, one of them is delayed and transmitted, and the signal transmission device on the reception side receives the left and right channels. The delay time difference is detected based on the time stamp information given to the signal, and the signals of both the left and right channels are restored to the original state without the time difference.

FIG. 10 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to the eighth embodiment. 5, the same parts as those in FIG. 5 are denoted by the same reference numerals, and detailed description is omitted.

In the signal transmission device 102 on the transmission side, the PES (Packetized Elementary Stream) multiplexing unit 1 is provided on the output side of the error detection code adders 12L and 12R, respectively.
5L and 15R are arranged. PES multiplexing unit 15L, 1
5R is for generating a PES packet.
The PES packet is an MPEG (Moving Picture Exper
ts Group), encoded video and audio data (elementary streams), data streams other than those standardized by MPEG, etc., are packetized with variable lengths, as shown in FIG. It is composed of

That is, the PES packet is composed of a PES header and a PES payload, and the PES header includes a control signal for performing scrambling on a PES packet basis, a flag indicating the presence or absence of a copyright, and a CRC (Cyclic).
Redundancy Check), PTS (Presentation Time Stamp) and DT as time stamp information.
S (Decoding Time Stamp) is included.

This embodiment utilizes this PTS or DTS. That is, when the PES multiplexing units 15L and 15R respectively generate the left channel and right channel PES packets, the PES headers of the PES
S or DTS is inserted. And like this, PES
Among the left channel and right channel PES packets with the PTS or DTS inserted in the header, the left channel PE
The S packet is given a predetermined time delay by the delay unit 14. This delay time is set to the maximum time of a burst error assumed on the wireless transmission path.

The PES of the left channel given this delay
The packet and the PES packet of the right channel to which no delay is given are input to the TS multiplexing unit 13 '. T
The S multiplexing unit 13 ′ includes a PES packet of the left channel to which the delay is given and a PES packet of the right channel to which no delay is given.
Each ES packet has a predetermined TS packet length (18
8 bytes), and a series of transport
Multiplex to stream (TS). FIG.
2 shows the relationship between the PES, TS, and program stream (PS).

On the other hand, in the signal transmitting device 202 on the receiving side, the TS separating section 21 ′ is connected to the signal transmitting device 1 on the transmitting side.
Transport stream (TS) sent from 02
Is separated for each TS packet, and the PES of the left channel and the PES of the right channel are combined based on the packet identifiers (PIDs) of these TS packets. Then, the PESs of the left channel and the right channel are input to the PES separation units 28L and 28R, respectively.

[0146] The PES separation units 28L and 28R are
The PES header is separated from each of the left channel and right channel PES output from the separation unit 21 ', and a PTS or DTS is extracted from the PES header. Then, the extracted PTS or DTS is sent to the time difference detection unit 2.
Enter 9 The time difference detection unit 29 detects the transmission time difference given between the PES of the left channel and the PES of the right channel, that is, the delay time by the delay unit 14 by comparing the PTS or DTS of the left channel and the right channel. Then, the detected delay time difference is provided to the variable delay device 27 '. The variable delay unit 27 ′ delays the PES of the right channel by the delay time given from the time difference detection unit 29, thereby obtaining the PES of the left channel and the PES of the right channel.
Return the ES to its original state with no mutual time difference.

With such a configuration, the elementary streams of the audio signals output from the audio encoders 11L and 11R are added with error detection codes for each frame by the error detection code adders 12L and 12R, respectively. After that, it is input to the PES multiplexing units 15L and 15R,
Here, each is composed of a PES packet. The PES packet has a PES payload as shown in FIG.
This is a variable-length packet to which an ES header is added. At this time, a PTS or DTS as time stamp information is inserted into the PES header as shown in FIG.

The PES packets of both the left and right channels output from the PES multiplexing units 15L and 15R are
Input to the multiplexing unit 13 ', where the fixed-length TS
After being separated into packets, they are multiplexed into one stream of transport stream (TS). Prior to the TS multiplexing, the PES packet of the left channel among the PES packets of the left and right channels is delayed by a predetermined amount in the delay unit 14. As a result, a transmission time difference corresponding to the maximum time of a burst error assumed on the wireless transmission path is formed between the PES packets of both the left and right channels.

That is, on the TS, the PES packet of the left channel and the PES packet of the right channel are arranged with a time difference equal to or longer than the maximum time length of a burst error assumed on the radio transmission path. FIG. 13 shows the relationship between this TS and the PES packets of both the left and right channels.

On the other hand, in the signal transmission device 202 on the reception side, the radio transmission signal transmitted from the signal transmission device 102 on the transmission side is received by the antenna and then demodulated by a radio demodulation unit (not shown). ', The signal is separated into a PES packet of the left channel and a PES packet of the right channel and input to the PES separation units 28L and 28R. PE
In the S separation units 28L and 28R, the PES header is separated from the PES packet, and the time stamp information inserted in the PES header, that is, PTS or DT
S is extracted and input to the time difference detection unit 29.

The time difference detector 29 compares the PTS or DTS of the left and right channels, and thereby detects the transmission time difference given between the PES packets of the left and right channels on the transmitting side. Then, the delay time corresponding to the detected time difference is provided to the variable delay device 27 '. Therefore, in the variable delay unit 27 ', the PES packet of the right channel among the PES packets of both the left and right channels is delayed by the given delay time, and as a result, the transmission time difference provided between the PES packets of the left and right channels is reduced. Is eliminated.

The PES packets of both the left and right channels are decoded by the audio decoders 23L and 23R after the error detectors 22L and 22R detect the presence or absence of a code error for each frame. At this time, the decoded signals of both the left and right channels are output from the error detectors 22L and 22L.
The signal is selected and output by the signal selection switches 24L and 24R in accordance with the detection result of the code error by the 2R.

For example, now that the quality of the wireless transmission path is good,
It is assumed that no code error has occurred in the PES packets of both the left and right channels. In this case, no error is detected by the error detectors 22L and 22R.
L and 24R are audio decoders 23L and 23R, respectively.
Is selected. Accordingly, in this case, the decoded signals output from the audio decoders 23L and 23R are output as the left-channel decoded signal ASLout and the right-channel decoded signal ASRout, respectively.

On the other hand, it is now assumed that fading or the like has occurred on the radio transmission path, and a burst error has occurred simultaneously in the TS packets of both the left and right channels in an arbitrary transmission section due to the effect. However, both left and right channel PE
The S packet is transmitted by the signal transmission device 102 on the transmission side.
After being given a time difference corresponding to the maximum time of a burst error assumed on a wireless transmission path, the signal is TS-multiplexed. For this reason, as described above, even if a burst error occurs simultaneously in the TS packets of the left and right channels in an arbitrary transmission section, the TS packets of the right and left channels that correspond to these left and right channels in time are: Since the signal is transmitted through another transmission section, there is a high possibility that the signal is correctly received without being affected by the burst error.

Therefore, the signal transmission device 202 on the receiving side
In the above, after the time difference between the left and right channels is eliminated by the variable delay device 27, error detection is performed, and the signal selection switches 24L and 24R select the signals of the left and right channels in accordance with the error detection result. Can be replaced with a signal of the other channel having a strong correlation corresponding to the signal in time. For this reason, even if both left and right channel signals multiplexed and transmitted in the same transmission section on the wireless transmission path cause a burst error, it is possible to reproduce both of the left and right channel signals.

As described above, according to the eighth embodiment, the PES packets of both the left and right channels are transmitted with the time difference corresponding to the maximum time length of the burst error assumed on the radio transmission path being transmitted. Even if the TS packets of both the left and right channels transmitted in the same transmission section on the transmission path cause a burst error, the PES packets transmitted by the TS packets of both the left and right channels can be reproduced together. In addition, in this embodiment, the PES
Time stamp information (PTS or D
The transmission time difference between the left and right channels is detected by the signal transmission device 202 on the receiving side using the TS), and the transmission time difference between the left and right channels is eliminated by the variable delay unit 27 'based on the detected time difference. I am trying to do it. For this reason,
For example, even if the time difference between the left and right channels becomes different from the transmission time difference given by the delay unit 14 when the TS multiplexing and the TS separation are performed, the change in the time difference is absorbed and the left and right channels are always synchronized. It is possible to reproduce the PES packet from which the PES packet has been obtained. In addition, there is no need to set the time difference information in the receiving apparatus 202 in advance, or to separately notify the time difference information from the transmitting side to the receiving side. For this reason,
It is possible to simplify the initial setting of a large number of signal transmission devices on the receiving side, and to easily cope with the case where the transmission time difference between signals needs to be changed.

(Ninth Embodiment) A ninth embodiment according to the present invention is described.
In the signal transmission device on the transmission side, the transmission signal of both the left and right channels is respectively given timestamp information, and then one of them is delayed so as to have a time difference between the signals of the left and right channels, and transmit and receive. In the signal transmission device on the side, the transmission time difference is detected from the time stamp information, and based on this, the time difference between the transmission signals of the left and right channels is eliminated to synchronize. At the same time, in the signal transmission device on the receiving side, the correlation between the signals between the left and right channels is extracted, and if a code error is detected in the received signal of one channel, the decoded frame of the other channel received correctly is detected. On the basis of the signal and the correlation value, a decoded frame signal of the channel in which the code error is detected is estimated.

FIG. 14 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to the ninth embodiment. 7 and FIG.
The same reference numerals are given to the same portions as 0, and the detailed description is omitted.

As in the eighth embodiment, PES multiplexing units 15L and 15R are provided in the signal transmission device 102 on the transmitting side, and PES packets are generated in the PES multiplexing units 15L and 15R, respectively. These PE
As shown in FIG. 11, PTS and DTS as time stamp information are inserted into the PES header of the S packet. Then, the PES packets of the left channel and the right channel into which the PTS or DTS is inserted are multiplexed into one system of TS in the TS multiplexing unit 13 '. Prior to the multiplexing, the PES packets of the left channel are delayed by a delay unit. 14
Accordingly, the delay is delayed by a time corresponding to the maximum time of the burst error assumed on the wireless transmission path.

On the other hand, the signal transmission device 203 on the receiving side includes the PES separation units 28L and 28R and the time difference detection unit 29
Is provided. In the PES separation units 28L and 28R, TS
The PES header is separated from each of the left channel and right channel PES output from the separation unit 21 ', and a PTS or DTS is extracted from the PES header. The time difference detector 29 calculates the P of the left channel and the right channel.
By comparing the TS or DTS, the transmission side detects a transmission time difference given between the left channel PES and the right channel PES, and supplies the detected transmission time difference to the variable delay unit 27 '. The variable delay unit 27 'delays the right channel PES by the delay time given from the time difference detection unit 29, thereby eliminating the transmission time difference between the left channel PES and the right channel PES. PES
Return to

With such a configuration, in the signal transmission device 102 on the transmission side, the PES packets of both the left and right channels are added with an ES header including PTS and DTS as time stamp information by the PES multiplexing units 15L and 15R. You. Then, the PES packet of the left channel is delayed by the delay unit 14, whereby
After a transmission time difference corresponding to the maximum time of a burst error assumed on a wireless transmission path is given between S packets, T
In the S multiplexing unit 13 ', the signal is multiplexed into one stream of TS.

On the other hand, in the signal transmission device 203 on the reception side, the radio transmission signal transmitted from the signal transmission device 102 on the transmission side is received by the antenna, and then demodulated by a radio demodulation unit (not shown). The signal is separated into a PES packet of the left channel and a PES packet of the right channel by the unit 21 ', and is inputted to the PES separation units 28L and 28R. In the PES separation units 28L and 28R,
The PES header is separated from the S packet, and the time stamp information inserted in this PES header, that is, PT
S or DTS is extracted and input to the time difference detection unit 29.

The time difference detector 29 compares the PTS or DTS of the left and right channels, and thereby detects the transmission time difference given between the PES packets of the left and right channels on the transmitting side. Then, the delay time corresponding to the detected time difference is provided to the variable delay device 27 '. Therefore, in the variable delay unit 27 ', of the PES packets of both the left and right channels, the PES packet of the right channel is delayed by the given delay time, and as a result, the transmission time difference provided between the PES packets of the left and right channels is reduced. Is eliminated.

Then, the synchronized PES packets of both the left and right channels are sent to the error detectors 22L and 22L, respectively.
After the presence or absence of a code error is detected for each frame in the 2R, the audio is decoded by the audio decoders 23L and 23R. These decoded signals are transmitted through the signal selection switches 24L and 24R as they are to ASLout and ASL unless the transmission quality of the wireless transmission path is good and no code error is detected.
Output as SRout.

On the other hand, if fading or the like occurs on the radio transmission path, and the signals of both the left and right channels are not correctly transmitted due to a burst error in an arbitrary transmission section due to the influence of the fading, the signal transmission device 20 on the receiving side
In 3, the right channel error detector 22R detects a code error in an arbitrary frame of the received signal of the right channel. Then, a switching control signal is output from the error detector 22R to the signal selection switch 24R, whereby the signal selection switch 24R switches from the audio decoder 23R to the other signal estimator 26 during the period in which the error is detected. .

Therefore, in this case, the left-channel decoded frame signal output from the audio decoder 23L is directly output as ASLout to the next-stage signal reproducing circuit (not shown), but a code error is detected. In the other right channel, instead of the right channel decoded frame signal output from the audio decoder 23R, the other signal estimator 26 calculates a normal left channel decoded frame signal and correlation information between the left and right channels. Is supplied as ASRout.

That is, even if a burst error occurs in both TS packets of each of the left and right channels in an arbitrary transmission section of the TS, a TS packet of each of the left and right channels that originally corresponds to the TS packet of these channels in time. Since a transmission time difference is given in advance on the transmission side between the times, there is a high possibility that correct reception can be performed without generating a burst error. Therefore, even if a burst error occurs in the PES packet of one channel, it is possible to reproduce the signal by compensating for the error based on the PES packet of the other channel that originally corresponds in time.

Further, the PES packet of the channel on which the burst error has occurred is estimated based on the correctly received signal of the other channel and the correlation information between the left and right channels extracted by the correlation extractor 25. As compared with the case where the PES packets of the left and right channels are simply replaced, the power and phase difference are compensated more accurately even when the signal correlation between the two channels is weak, thereby impairing the natural feeling. High quality stereo signals can be reproduced.

Further, in the present embodiment, the transmission time difference between the left and right channels is detected by the signal transmission device 203 on the receiving side using the time stamp information (PTS or DTS) inserted in the PES header, and the detected time difference is detected. Based on the time difference, a variable delay 27 'is used to eliminate the transmission time difference between the left and right channels. Therefore, for example, TS
Even if the time difference between the left and right channels becomes different from the transmission time difference given by the delay unit 14 during the multiplexing and TS separation, the change in the time difference is absorbed and the left and right channels are always synchronized. The reproduced PES packet can be reproduced. In addition, there is no need to set the time difference information in the receiving apparatus 202 in advance, or to separately notify the time difference information from the transmitting side to the receiving side. For this reason, there are advantages that the initial setting of a large number of signal transmitting devices on the receiving side can be simplified, and that it is possible to easily cope with a case where the transmission time difference between the signals needs to be changed.

(Tenth Embodiment) In a tenth embodiment according to the present invention, in a digital stereo transmission system, a signal transmission device on the transmitting side extracts a correlation between both left and right channels, and extracts this correlation information. Each side signal is added to the left channel signal and the right channel signal as side information, and time stamp information is added to the transmission signals of both the left and right channels. Then, one of them is delayed so as to have a time difference between the signals of the left and right channels. To send. And
The signal transmission device on the receiving side detects the transmission time difference from the above time stamp information, eliminates the time difference between the transmission signals of the left and right channels based on this, and synchronizes, and detects a code error in one of the channels. In this case, a decoded signal is estimated from the correlation information added as side information and the decoded signal of the channel having no code error, and is output.

FIG. 15 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to the tenth embodiment. 8, the same parts as those in FIG. 8 are denoted by the same reference numerals, and detailed description is omitted.

First, in the signal transmission device 501 on the transmission side, the PES of both the left and right channels output from the error detection code adders 54L and 54R are respectively converted into PES multiplexers 57.
L, 57R. These PES multiplexing units 57
In L and 57R, PES packets are respectively generated. In the PES header of these PES packets, FIG.
As shown in FIG. 1, PTS and DTS as time stamp information are inserted. And this PTS or DTS
The PES packets of the left channel and the right channel into which are inserted are multiplexed into one TS by the TS multiplexing unit 55 '. Prior to this multiplexing, the PES packets of the left channel are delayed by the delay unit 56. Accordingly, a transmission time difference corresponding to the maximum time of a burst error assumed on the wireless transmission path is provided between the PES packets of both the left and right channels.

On the other hand, the signal transmission device 601 on the receiving side includes the PES separation units 68L and 68R and the time difference detection unit 69
Is provided. In the PES separation units 68L and 68R, TS
The PES header is separated from each of the PESs of the left channel and the right channel output from the separation unit 61 ', and the PTS or DTS is extracted from the PES header. The time difference detector 69 calculates the P of the left channel and the right channel.
By comparing the TS or the DTS, the transmission side detects a transmission time difference given between the left channel PES and the right channel PES, and supplies the detected transmission time difference to the variable delay device 67 '. The variable delay device 67 'delays the PES of the right channel by the delay time given from the time difference detector 69, thereby eliminating the transmission time difference between the PES of the left channel and the PES of the right channel. PES
Return to

With such a configuration, in the signal transmission device 501 on the transmission side, the PES of the left channel and the PES of the right channel to which the side signal is added are separated by the error detection code adders 54L and 54R into error detection codes. Are added to the PES multiplexing units 15L and 15R.
Then, in the PES multiplexing units 15L and 15R, an ES header including PTS and DTS as time stamp information is added to form a PES packet.

The PES packet of the left channel among the PES packets of both the left and right channels is
6, a transmission time difference corresponding to the maximum time of a burst error assumed on the wireless transmission path is provided between the PES packets of both the left and right channels. Then, the PES packets of both the left and right channels to which the time difference has been given are multiplexed by the TS multiplexing unit 55 'into one series of TS.

On the other hand, in the signal transmission device 601 on the reception side, the radio transmission signal transmitted from the signal transmission device 501 on the transmission side is received by an antenna and then demodulated by a radio demodulation unit (not shown). The PES packet is separated into a PES packet for the left channel and a PES packet for the right channel by the unit 61 ', and is input to the PES separation units 68L and 68R. In the PES separation units 68L and 68R,
The PES header is separated from the S packet, and the time stamp information inserted in this PES header, that is, PT
S or DTS is extracted and input to the time difference detector 69.

The time difference detector 69 compares the PTS or DTS of the left and right channels, and thereby detects the transmission time difference given between the PES packets of the left and right channels on the transmitting side. Then, the delay time corresponding to the detected time difference is provided to the variable delay device 67 '. Therefore, in the variable delay unit 67 ', of the PES packets of both the left and right channels, the PES packet of the right channel is delayed by the given delay time, and as a result, the transmission time difference provided between the PES packets of the left and right channels is reduced. Is eliminated.

Then, the synchronized PES packets of the left and right channels are sent to error detectors 62L and 62L, respectively.
After the presence or absence of a code error is detected for each frame in 2R, decoding is performed by the audio decoders 63L and 63R. These decoded signals are transmitted through the signal selection switches 64L and 64R as they are to ASLout and ASL unless the transmission quality of the wireless transmission path is good and no code error is detected.
Output as SRout.

On the other hand, it is assumed that fading or the like occurs on the radio transmission path, and the signals of both the left and right channels are not correctly transmitted due to a burst error in an arbitrary transmission section due to the effect. However, the transmission signals of both the left and right channels are multiplexed to the TS after a transmission time difference corresponding to the maximum time of the burst error is given in advance by the signal transmission device 501 on the transmission side. For this reason, as described above, even if the signal frames of the left and right channels simultaneously cause a burst error in an arbitrary transmission frame section, the signal frames of the right and left channels that are originally temporally corresponding to these left and right channels are Is transmitted in another transmission frame section, there is a high possibility that it will be correctly received without being affected by the burst error.

Therefore, the signal transmission device 601 on the receiving side
In the above method, after the time difference between the left and right channels is eliminated by the variable delay device 67 ′, error compensation is performed based on the correctly received signal of the other channel to reproduce the signal of the channel in which the burst error has occurred. Becomes possible.

Further, in the present embodiment, as described in the seventh embodiment, the correlation information notified from the transmitting side as side information is used in the error compensation.
That is, the R-correlation information added as side information to the received signal of the left channel is decoded by the R-correlation decoder 65L, and the R signal is estimated from the decoded R-correlation information and the decoded signal of the left channel without code error. The decoded signal of the right channel is estimated by the unit 66L. Then, the estimated right channel decoded signal is selected by the signal selection switch 64R, supplied to a signal reproducing circuit (not shown), and reproduced as a right channel audio signal.

Since no code error has occurred in the left channel, the decoded signal of the left channel output from the audio decoder 63L is transmitted to the signal selection switch 64L.
Is supplied to the signal reproduction circuit as it is, and reproduced as an audio signal of the left channel.

Similarly, when a transmission error occurs in an arbitrary frame of the left channel received signal, the L correlation information added to the right channel received signal is converted to the L correlation decoder 65.
It is decoded by R, and the decoded signal of the left channel is estimated from the decoded L correlation information and the decoded signal of the right channel.
Then, the estimated left-channel decoded signal is selected by the signal selection switch 64L, supplied to a signal reproducing circuit (not shown), and reproduced as a left-channel audio signal.

Since no code error has occurred in the received signal for the right channel, the audio decoder 63
The decoded signal of the right channel output from R is directly supplied to the signal reproduction circuit via the signal selection switch 64R,
Reproduced to the right channel audio signal.

As described above, according to the tenth embodiment,
In the signal transmission device 501 on the transmission side, the transmission time difference corresponding to the maximum time length of the burst error assumed on the radio transmission path is given to the PES packets of both the left and right channels, and then TS multiplexing is performed. There is less fear that the signals of the left and right channels corresponding to the time will cause a burst error at the same time, so that even if fading occurs for a long time, the signals of the left and right channels can be reproduced more reliably. .

[0186] Also, using the time stamp information (PTS or DTS) inserted in the PES header, the signal transmission device 203 on the receiving side detects the transmission time difference between the left and right channels, and based on the detected time difference, Variable delay 27 '
This eliminates the transmission time difference between the left and right channels. Therefore, even if the time difference between the left and right channels becomes different from the transmission time difference given by the delay unit 14 when, for example, TS multiplexing and TS separation are performed, the change in the time difference is absorbed and the difference between the left and right channels is reduced. Thus, a synchronized PES packet can always be reproduced. In addition, there is no need to set the time difference information in the receiving apparatus 202 in advance, or to separately notify the time difference information from the transmitting side to the receiving side. For this reason, there are advantages that the initial setting of a large number of signal transmitting devices on the receiving side can be simplified, and that it is possible to easily cope with a case where the transmission time difference between the signals needs to be changed.

Further, in the tenth embodiment, the correlation between the signals of the left and right channels is extracted on the transmitting side, and the correlation information is added to the left and right main signals as side signals and transmitted. When a code error is detected in one of the channels, a decoded signal is estimated from the decoded signal of the channel received correctly and the correlation information transmitted together with the signal, and the estimated decoded signal is It is used for signal reproduction in place of the decoded signal in which the code error is detected.

Therefore, compared with the case where the signal transmission device 601 on the receiving side extracts the correlation of the signal between the left and right channels based on the received signal, the decoded signal can always be estimated using accurate correlation information. . Therefore, more accurate error compensation can be performed, and thereby a high-quality audio signal can be reproduced.

(Other Embodiments) In the fourth and seventh embodiments, in the signal transmission devices 50 and 500 on the transmission side, the correlation of the right channel signal to the left channel signal and the left channel Are extracted, but one of them may be extracted, and this correlation information may be added to the signals of the left and right channels as side information and transmitted. In this case, the correlation information may be transmitted by independent channels separately from the left and right channel signals. At this time, if the correlation is in the form of an adaptive filter, an inverse filter is formed for one of the signals. Should work.

In the fifth to seventh embodiments,
Although the transmission side delays the left channel signal for transmission, the right channel may be delayed. Further, a delay device of a type capable of variably controlling the delay amount is used as the delay device, and the delay amount is configured to be variably set periodically or adaptively in accordance with the time length of the burst error occurring on the wireless transmission path. Is also good. In this way, it is possible to appropriately cope with a time change of a burst error due to a change in a use environment or the like.

Further, the delay unit may be arranged at the preceding stage, instead of being arranged at the subsequent stage of the error detecting code adder, or may be arranged at the preceding stage of the audio encoder.

Further, in the eighth to tenth embodiments, taking the MPEG system as an example, the transmission time difference between the left and right channel signals is detected by using the PTS or DTS already included in the PES header. Was described. However, the present invention is also applicable to a system that does not transmit time stamp information. That is,
The transmitting side inserts timestamp information into each of the information signals to be transmitted at regular or arbitrary timings and transmits it. The receiving side extracts the timestamp information from each received information signal and detects the time difference And
Based on this detection result, the transmission time difference between the information signals is eliminated.

In each of the above embodiments, a stereo audio transmission system has been described as an example. However, the transmission signal is not limited to a stereo audio signal. It may be a signal or a video signal.

In addition, the method of extracting the correlation, the configuration of each signal transmission device on the transmission side and the reception side, the multiplexing method of the transmission signals of a plurality of channels, the type of the transmission path, etc. are within the scope of the present invention. Various modifications can be made.

[0195]

As described above in detail, according to the present invention, in the signal transmission device on the receiving side, the reception quality of at least one of the plurality of signals transmitted from the transmission side is monitored, and the reception quality is less than a predetermined level. In the case where the received signal quality decreases, the signal whose reception quality has deteriorated is reproduced by the quality compensating means based on another transmitted sound signal.

Therefore, according to the present invention, if one of a plurality of signals having a correlation with each other is received normally, even if a signal having a small correlation in the time axis direction is received even when information having a small correlation in the time axis direction is received. , Effective quality compensation can be performed.

On the other hand, in another invention, in a system for transmitting a plurality of signals having correlation with each other from a transmission side to a reception side, transmission timings of the signals are made different from each other by a predetermined time on the transmission side. Then, the reception side monitors the reception quality of each of the plurality of signals transmitted from the transmission side, and when it is detected that the reception quality of any signal has dropped below a predetermined level, the reception of the signal The degraded section is reproduced based on a corresponding section of another signal arriving with the time difference of the predetermined time. Therefore, according to another aspect of the present invention, even when the reception quality of a plurality of signals is reduced at the same time, each of the received signals can be compensated and reproduced.

In still another invention, the transmitting side attaches time stamp information to each of a plurality of signals to be transmitted for each section corresponding to the time, and then adjusts the transmission timing of the plurality of signals to each other. The transmission is made different for a predetermined time. On the other hand, on the receiving side, time stamp information is extracted from each of the plurality of signals transmitted from the transmitting side, and a time difference between the plurality of transmitted signals is detected based on the extracted time stamp information, Based on the detected time difference, the time difference between the plurality of signals provided on the transmission side is eliminated. Then, for each of the plurality of signals,
The reception quality is monitored, and when it is detected that the reception quality of an arbitrary signal has dropped below a predetermined level, the reception quality reduction section of the signal corresponds to the time before the time difference is formed in other signals. Playback is based on the section.

Therefore, according to another invention, the original signal is restored by eliminating the transmission time difference given between each signal based on the time stamp information given to each signal. There is no need to set the time difference information in the device on the side in advance or to notify the time difference information from the transmitting side to the receiving side. For this reason, the initial setting of a large number of receiving-side devices can be simplified, and it is possible to easily cope with the case where the transmission time difference between signals needs to be changed. Further, for example, even if the time difference given between a plurality of signals at the time of demultiplexing changes, it is possible to absorb the change in the time difference and always accurately synchronize the signals.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to a first embodiment of the present invention.

FIG. 2 is a circuit block diagram showing a main configuration of a signal transmission device on a receiving side in a digital stereo transmission system according to a second embodiment of the present invention.

FIG. 3 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to a third embodiment of the present invention.

FIG. 4 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to a fourth embodiment of the present invention.

FIG. 5 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to a fifth embodiment of the present invention.

FIG. 6 is a timing chart used to explain the operation of the system shown in FIG. 5;

FIG. 7 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to a sixth embodiment of the present invention.

FIG. 8 is a circuit block diagram illustrating a main configuration of a digital stereo transmission system according to a seventh embodiment of the present invention.

FIG. 9 is a timing chart used to explain the operation of the system shown in FIG. 8;

FIG. 10 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to an eighth embodiment of the present invention.

FIG. 11 is a diagram showing a structure of a PES packet.

FIG. 12 is a view showing the interrelationship of each stream in the MPEG-2 system.

FIG. 13 is a timing chart used to explain the operation of the system shown in FIG. 10;

FIG. 14 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to a ninth embodiment of the present invention.

FIG. 15 is a circuit block diagram showing a main configuration of a digital stereo transmission system according to a tenth embodiment of the present invention.

[Description of Signs] 10, 30, 50, 100, 102, 103, 500,
501 ... Transmission-side signal transmission device 20, 20 ', 40, 60, 200, 201, 202,
203, 600, 601... Receiving-side signal transmission devices 11 L, 11 R, 51 L, 51 R... Audio encoders 12 L, 12 R, 33 S, 54 L, 54 R... Error detection code adders 13, 34, 55. 55 '... TS multiplexing section 14, 27, 56, 67 ... delay unit 15L, 15R ... PES multiplexing section 21, 41, 61 ... separating section 21', 61 '... TS separating section 22L, 22R, 42S, 62L, 62R ... Error detectors 23L, 23R, 63L, 63R ... audio decoders 24L, 24R, 47L, 47R, 64L, 64R ... signal selection switches 25 ... correlation extractors 26 ... other signal estimators 27 ', 67' ... variable delay devices 28L , 28R, 68L, 68R PES separation unit 29, 69 Time difference detection unit 31M Adder 31S Subtractor 32M Main signal encoding 32S ... sub signal encoder 33M ... error correction code adder 42M ... error corrector 43M ... main signal decoder 43S ... sub signal decoder 44L ... L correlation extractor 44R ... R correlation extractor 45L ... L signal estimator 45R R signal estimator 46M Subtractor 46S Adder 52L R correlation extractor 52R L correlation extractor 53L, 53R Encoder 65L R correlation decoder 65R L correlation decoder 66L R signal estimation Device 66R ... L signal estimator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuriko Tsukahara 70 Yanagimachi, Saiwai-ku, Kawasaki City, Kanagawa Prefecture Inside the Toshiba Yanagimachi Plant Co., Ltd. Inside

Claims (15)

[Claims] 1. A signal transmission device used in a digital signal transmission system for transmitting a plurality of signals, wherein at least one of the plurality of transmitted signals is
Quality monitoring means for monitoring the reception quality; and when the quality monitoring means detects that the reception quality of the signal to be monitored has fallen below a predetermined level, the signal having the reduced reception quality is used as another signal. A signal transmission device comprising: quality compensation means for reproducing a signal based on the signal. 2. The quality compensating unit, when the quality monitoring unit detects that the reception quality of the signal to be monitored has dropped below a predetermined level, converts the signal with the lowered reception quality into another sound signal. The signal transmission device according to claim 1, wherein the signal transmission device is replaced with a signal. 3. The quality compensating means includes a correlation extracting means for extracting a correlation between the plurality of transmitted signals, and the quality monitoring means reduces a reception quality of a signal to be monitored to below a predetermined level. 2. The signal transmission according to claim 1, wherein when the signal is detected, the signal whose reception quality is reduced is reproduced based on another sound signal and the correlation extracted by the correlation extraction unit. apparatus. 4. A signal transmission device used in a digital signal transmission system for mutually calculating a plurality of transmission signals having a correlation with each other to generate a plurality of calculation results and transmitting these calculation results. Signal reproducing means for performing a reverse operation on the plurality of calculated results and reproducing a plurality of first received signals corresponding to the plurality of transmission signals, and the transmitted plurality of calculated results and the reverse operation The correlation with each of the plurality of first received signals reproduced by
Signal estimating means for respectively estimating a plurality of second received signals corresponding to the plurality of transmission signals based on the correlation and the transmitted operation result; and receiving the information on the transmitted operation result. Quality monitoring means for monitoring quality; and, as a result of monitoring by the quality monitoring means, selecting a first received signal reproduced by the signal reproducing means when the reception quality of the information of the operation result is equal to or higher than a predetermined level. And when the reception quality of the information of the calculation result is lower than a predetermined level, the second signal estimated by the signal estimation means is output.
And a signal selecting means for selecting and outputting the received signal. 5. A digital signal transmission system for transmitting a plurality of signals from a transmission-side signal transmission device to a reception-side signal transmission device, wherein the transmission-side signal transmission device transmits another signal for each of the plurality of signals. A correlation extracting means for respectively obtaining correlation information representing a correlation with, and adding, to each of the plurality of signals, correlation information with another signal obtained by the correlation extracting means, and after the correlation information is added Transmitting means for transmitting a plurality of signals respectively, the receiving-side signal transmitting apparatus, a signal reproducing means for reproducing a plurality of signals transmitted from the transmitting-side signal transmitting apparatus, respectively, and the signal reproducing means Based on each of the plurality of decoded signals output from and the correlation information added to the decoded signal, a signal estimating means for estimating a decoded signal of each other channel, Quality monitoring means for monitoring the reception quality of each of the plurality of signals transmitted from the signal transmission device on the transmitting side; and, based on the monitoring result by the quality monitoring means, the reception quality of an arbitrary signal having a predetermined level or higher. And a signal selecting means for selecting and outputting a decoded signal reproduced by the signal reproducing means, and selecting and outputting a corresponding signal estimated by the signal estimating means when the reception quality is lower than the predetermined level. A digital signal transmission system comprising: 6. A method for obtaining correlation information representing a correlation between each of a plurality of signals and another signal, and adding, to each of the plurality of signals, correlation information with the obtained other signal. In a signal transmission device used in a digital signal transmission system that respectively transmits a plurality of signals after information is added, a signal reproduction unit that reproduces a plurality of signals transmitted from the transmission-side signal transmission device, Based on each of the plurality of signals output from the signal reproducing unit and the correlation information added to the signal, a signal estimating unit for estimating each of the other signals, and a signal transmitting device on the transmitting side. Quality monitoring means for monitoring the reception quality of each of the plurality of transmitted signals; and based on the monitoring result by the quality monitoring means, if the reception quality of any received signal is equal to or higher than a predetermined level. A signal selecting means for selecting and outputting a signal reproduced by the signal reproducing means, and selecting and outputting a corresponding signal estimated by the signal estimating means when the reception quality is less than the predetermined level. A signal transmission device comprising: 7. A digital signal transmission system for transmitting a plurality of signals having correlation with each other from a transmission-side signal transmission device to a reception-side signal transmission device, wherein the transmission-side signal transmission device transmits the plurality of signals. The signal transmission device on the receiving side includes a time difference forming unit that makes timings different from each other by a predetermined time, based on a time difference formed on the transmission side for each of the plurality of signals transmitted from the signal transmission device on the transmission side. Return time difference recovery means, quality monitoring means for monitoring the reception quality of each of the plurality of signals transmitted from the signal transmission device on the transmission side, and reception quality of an arbitrary signal determined by the quality monitoring means. When it is detected that the signal quality has dropped below the level, the reception quality reduction section of the signal is defined as a section corresponding to the time before the time difference is formed in other signals. A digital signal transmission system, comprising: a quality compensating unit for reproducing based on the digital signal. 8. A digital signal transmission system for transmitting a plurality of signals having correlation with each other from a signal transmitting device on a transmitting side to a signal transmitting device on a receiving side, wherein the signal transmitting device on the transmitting side comprises: A time stamp providing means for providing time stamp information for each section corresponding to the time, and transmission timings of a plurality of signals to which the time stamp information is provided by the time stamp providing means are different from each other by a predetermined time. The reception-side signal transmission device extracts time stamp information from each of a plurality of signals transmitted from the transmission-side signal transmission device, and based on the extracted time stamp information. A time difference detecting means for detecting a time difference between the plurality of transmitted signals, and a time difference detected by the time difference detecting means. A time difference restoring unit that restores a time difference between the plurality of signals transmitted from the transmission side based on the time difference; and monitoring a reception quality of each of the plurality of signals transmitted from the transmission side signal transmission device. Quality monitoring means for detecting the reception quality of an arbitrary signal having fallen below a predetermined level by the quality monitoring means. A digital signal transmission system comprising: a quality compensating unit for reproducing based on a time-corresponding section of the digital signal. 9. The quality compensating unit, when the quality monitoring unit detects that the reception quality of an arbitrary signal has dropped below a predetermined level, sets the reception quality reduction section of the signal to another transmission quality. 9. The digital signal transmission system according to claim 7, wherein a section corresponding to a time before the time difference is formed in the received signal is replaced. 10. A correlation monitoring means for detecting a correlation in a time-corresponding section before forming the time difference among a plurality of signals transmitted with a mutual time difference of the predetermined time. Having, when the quality monitoring means detects that the reception quality of any signal has dropped below a predetermined level, the reception quality reduction section of the signal,
9. The digital signal transmission system according to claim 7, wherein the estimation is performed based on a temporally corresponding section of the other transmitted signal before the time difference is formed and a correlation detected by the correlation monitoring unit. . 11. Time-stamp information is added to each of a plurality of signals for each time-corresponding section, and transmission timings of the plurality of signals to which the time-stamp information is added are made different from each other by a predetermined time. In the signal transmission device that receives the plurality of signals transmitted from the transmission-side signal transmission device, extracting time stamp information from each of the plurality of signals transmitted from the transmission-side signal transmission device, Time difference detecting means for detecting a time difference between the plurality of transmitted signals based on each time stamp information; and, based on the time difference detected by the time difference detecting means, between the plurality of signals transmitted from a transmitting side. A time difference restoring means for restoring the time difference, and a product for monitoring the reception quality of each of the plurality of signals transmitted from the signal transmission device on the transmission side. Quality monitoring means, and when the quality monitoring means detects that the reception quality of an arbitrary signal has dropped below a predetermined level, the reception quality reduction section of the signal is regarded as a time interval before a time difference is formed in another signal. And a quality compensating means for reproducing based on a section corresponding to the signal transmission apparatus. 12. A digital signal transmission system for transmitting a plurality of signals having a correlation with each other from a transmission-side signal transmission device to a reception-side signal transmission device, wherein the transmission-side signal transmission device comprises: Correlation extraction means for respectively obtaining correlation information representing a correlation with another signal for each; correlation information addition means for respectively adding correlation information with another signal obtained by the correlation extraction means to each of the plurality of signals A plurality of signals to which the correlation information has been added by the correlation information adding means, and a time difference forming means for making transmission timings differ from each other by a predetermined time, wherein the signal transmission device on the reception side comprises: A reproducing unit for reproducing a plurality of signals transmitted from the transmission device; and a plurality of reproduced signals output from the reproducing unit. A signal estimating unit for estimating each of the other reproduced signals based on the correlation information added to the reproduced signal, and monitoring reception qualities of a plurality of signals transmitted from the signal transmission device on the transmission side. Based on the monitoring result by the quality monitoring means, when the reception quality of an arbitrary signal is equal to or higher than a predetermined level, selects and outputs the reproduction signal reproduced by the reproduction means, and adjusts the reception quality. When the signal level is less than the predetermined level, instead of the signal in the reception quality degraded section, a signal in the section corresponding to the time corresponding to the time before the time difference is formed in the other reproduction signal estimated by the signal estimating means is output. A digital signal transmission system comprising signal selection means. 13. A digital signal transmission system for encoding a plurality of signals having a correlation with each other and transmitting the encoded signals from different signal transmission devices on a transmission side to signal reception devices on a reception side via different channels. The transmission device, for each of the plurality of signals, a correlation extraction unit that extracts correlation information indicating a correlation with another signal, respectively, encoding the plurality of signals and the correlation information extracted by the correlation extraction unit, respectively; Transmitting means for transmitting a signal through a different channel after forming a predetermined time difference, wherein the signal transmitting device on the receiving side transmits a plurality of signals and correlations transmitted from the signal transmitting device on the transmitting side via different channels. Decoding means for decoding information respectively; decoding signals of a plurality of channels output from the decoding means; A signal estimating unit for estimating a decoded signal of another channel based on the related correlation information, and monitoring reception qualities of a plurality of signals transmitted from the signal transmitting device on the transmission side via different channels, respectively. Based on the monitoring result of the quality monitoring means, when the reception quality of an arbitrary channel is equal to or higher than a predetermined level, selects and outputs a decoded signal decoded by the decoding means, and When the signal level is less than the predetermined level, a signal in a section corresponding to a temporally corresponding section before the formation of the time difference in the decoded signal of the other channel estimated by the signal estimating means is output instead of the signal in the section of reduced reception quality. Digital signal transmission system comprising: 14. A digital signal transmission system for transmitting a plurality of signals having correlation with each other from a signal transmitting device on a transmitting side to a signal transmitting device on a receiving side, wherein the signal transmitting device on the transmitting side comprises: Correlation extraction means for respectively obtaining correlation information representing a correlation with another signal for each; correlation information addition means for respectively adding correlation information with another signal obtained by the correlation extraction means to each of the plurality of signals Time stamp adding means for adding time stamp information to each of the plurality of signals to which the correlation information is added by the correlation information adding means for each section corresponding to the time; Time difference forming means for making the transmission timings of a plurality of signals respectively provided with stamp information different from each other by a predetermined time The reception-side signal transmission device extracts time stamp information from each of the plurality of signals transmitted from the transmission-side signal transmission device, and transmits the time stamp information based on the extracted time stamp information. Time difference detecting means for detecting a time difference between a plurality of signals; reproducing means for respectively reproducing a plurality of signals transmitted from the signal transmitting device on the transmitting side; and a plurality of reproduced signals output from the reproducing means. Based on each and the correlation information added to the reproduction signal, a signal estimation unit for estimating each of the other reproduction signals, and a reception quality of a plurality of signals transmitted from the signal transmission device on the transmission side. Quality monitoring means for monitoring each, and based on the monitoring result by the quality monitoring means, when the reception quality of an arbitrary signal is equal to or higher than a predetermined level, the signal is reproduced by the reproduction means. A raw signal is selected and output, and when the reception quality is lower than the predetermined level, a time response before a time difference is formed in another reproduction signal estimated by the signal estimation unit is used instead of the signal in the reception quality reduction section. A signal selecting means for selecting and outputting a signal of the section to be performed based on the time difference detected by the time difference detecting means. 15. A digital signal transmission system for encoding a plurality of signals having correlation with each other and transmitting the encoded signals from different signal transmission devices on a transmission side to signal transmission devices on a reception side via different channels. The transmission device, for each of the plurality of signals, a correlation extraction unit that respectively extracts correlation information indicating a correlation between a signal of itself and another signal, and each of the plurality of signals is extracted by the correlation extraction unit. Multiplexing means for multiplexing the correlation information between the own signal and another signal, and time stamp information for each of a plurality of multiplexed signals obtained by the multiplexing means for each time-corresponding section. And a transmission time of a plurality of multiplexed signals to which time stamp information is respectively added by the time stamp adding means. And a time difference forming means for making the transmission time different from each other by a predetermined time, wherein the reception-side signal transmission device performs a time stamp from each of the plurality of multiplexed signals transmitted from the transmission-side signal transmission device via different channels. Time difference detecting means for extracting information, detecting a time difference between the plurality of transmitted multiplexed signals based on the extracted time stamp information, and transmitting the information via different channels from the signal transmission device on the transmission side. Separating means for separating each of the plurality of multiplexed signals into a signal and correlation information, and signal estimation for estimating a signal of another channel based on the signal and correlation information separated by the separating means. Means, and quality monitoring means for monitoring the reception quality of a plurality of signals transmitted from the transmission-side signal transmission device via different channels, respectively. When the reception quality of an arbitrary channel is equal to or higher than a predetermined level, the signal separated by the separation unit is selected and output based on the monitoring result of the channel. When the reception quality is lower than the predetermined level, the signal of the reception quality reduction section is selected. Alternatively, a signal of a section corresponding to the time before forming the time difference in the decoded signal of the other channel estimated by the signal estimating means is selected and output based on the time difference detected by the time difference detecting means. Digital signal transmission system comprising: