JPH11298999A - Multi-channel pcm sound signal transmitting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize highly efficient transmission for transmitting a signal with a synchronizing signal with one cable by time-dividing a sound signal to be transmitted into the signals of a left channel and a right channel at each prescribed sampling time and dividing and arranging the signal in a prescribed order in respective time areas. SOLUTION: LR lock signals and serial clock signals are supplied to the A/D converters 211 -213 of a multichannel PCM sound signal transmission system. The A/D converters convert inputted sound signals into digital signals and supply PCM signals to a time divisional multiplexer 25. The LR clock/serial clock signals and AUX signals being other additional information and synchronizing signals are supplied to the time divisional multiplexer 25. They are time- dividedly mutliplexed and it is transmitted by one cable as one multichannel PCM signal. On a reception side, a time divisional separator 26 receives the signals, the respective signals are reproduced based on the synchronizing signal, the signals are transmitted to D/A converters 241 -243 , and they are outputted as the sound signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel audio signal transmission system using a PCM signal.

[0002]

2. Description of the Related Art As a transmission method of digital audio signals between devices, there are a method of directly transmitting a PCM signal and a transmission method of channel coding. Some channel-coded transmission systems have become international standards, and the AES / EBU format has been established for business use, and the IEC standard has been established for consumer use. Both of these are 2-channel (LR channel) stereo systems. This is related to the transmission method. FIG. 4 shows a schematic configuration of a system for directly transmitting a PCM signal, which will be described below. On the transmitting side, the input analog stereo audio signal is converted into a PCM signal by an A / D converter and transmitted.
In order to restore the M signal to an analog signal, it is necessary to transmit an LR clock signal for distinguishing the LR channel, a serial clock signal, and possibly a master clock signal. The receiving side performs D / A conversion from the transmitted PCM signal and clock signal to obtain an analog stereo audio signal.

FIG. 6 shows a configuration of a PCM transmission signal waveform, which will be described below. In this transmission of stereo sound, the number of sampling bits is 16 bits, and the sampling frequency is 48 KHz. The positive side of the LR clock signal (48 KHz) is set to the L channel and the negative side is set to the R channel.
It is assumed that data takes the form of MSB (Most Significant Bit) leading MSB. In the case of PCM data 1, A in FIG.
The serial clock signal frequency of the / D converter is 3.072M
In Hz, the L period and the R period can each insert 32-bit data. However, as described above, since the A / D converter is a 16-bit sampling A / D converter, each of the first half period 1
The PCM data appears at the top of the MSB in 16 bits of 4, 15 and the 16 bits of the second half are empty.
In the case of PCM data 2, the serial clock signal frequency is 1.536 MHz, and 16 bits each of 16 bits in the L period 16 and the R period 17 are 16 bits of PCM data, MSB first.

FIG. 5 shows a block diagram of a transmission system based on the AES / EBU interface standard, and the operation will be described below. The A / D converter 21 converts the L audio signal and the R audio signal into PCM signals, respectively.
It is supplied to the ES / EBU encoder 22. Where P
The CM signal is subjected to channel coding and biphase mark conversion using an LR clock signal and a serial clock signal to generate an AES / EBU signal. AES
The / EBU signal can transmit a two-channel stereo signal, a synchronization signal used for clock reproduction, and some auxiliary information through a single shielded cable or coaxial cable. This AES / EBU signal is
In the BU decoder 23, the reproduction of the clock signal and the inverse conversion of the biphase mark are performed, and the reproduced PCM signal, L
The R clock signal and the serial clock signal are sent to the D / A converter 24, and the original L audio signal and R audio signal are output.

FIG. 7 shows the structure of an AES / EBU interface signal, which will be described. As shown in FIG. 7, the audio data is transmitted by time-division multiplexing of an audio sample word, a synchronization preamble, AUX data, and other information V, U, C, and P. In the synchronization preamble, M indicating the left channel and W indicating the right channel appear alternately, and indicate which channel the subsequent data is. The audio data forms one block of 192 frames, and the synchronization preamble of the first subframe of the block is B. These M, W, and B have different code configurations and can be identified. AUX data, audio sample words, V, U, C, P data are
Since bi-phase mark modulation is performed, AES /
The transmission bit rate in the EBU transmission method is 6.144M
bps.

[0006]

In recent digital broadcasting and digital video discs (hereinafter referred to as DVDs), 4-channel multi-stereo, 5.1
Channel multi-stereo is used. FIG. 8 shows the arrangement of speakers on the reproduction side, and multi-stereo will be described. In the 4-channel multi-stereo, it is composed of two channels of L and R at the front and two channels of LS and RS at the rear. The 5.1-channel multi-stereo is configured with a total of four channels, a center C channel and a US channel for reproducing a signal having a frequency of 200 Hz or less, in addition to the front L and R channels, and the rear has L channels.
There are two channels, S and RS, and a total of six channels. The 5.1 channel is called US
This is because the channel is dedicated to a low frequency band of 200 Hz, and this is set to 0.1 channel. In any case, a transmission path of six channels is required. As described above, in the conventional PCM direct transmission system, transmission of a 6-channel PCM signal requires three transmission lines for PCM signals and a line for transmitting a clock, and further has the disadvantage that additional information cannot be transmitted. is there. The AES / EBU transmission system does not require a line for transmitting a clock, but requires three cables to transmit a signal of six channels, and a transmission bit rate of 6.144 Mbps. Is a disadvantage. The present invention eliminates these drawbacks and conventionally uses an AES / EBU interface to implement 6
When transmitting channel stereo, use 3 cables
The transmission bit rate of each cable is 6.144Mbp
The purpose of the present invention is to realize an efficient 6-channel stereo transmission system capable of transmitting a single cable with a transmission bit rate of 6.144 Mbps and a synchronization signal.

[0007]

According to the present invention, in order to achieve the above object, in a PCM digital multi-channel audio signal transmission, a multi-channel PCM audio signal to be transmitted is shifted to the left (L) every predetermined sampling time. ) Channel and right (R) channel signal, and in the time domain of the L channel, the L channel signal of each channel is divided and arranged in a predetermined order. The channel signal is divided, arranged and transmitted in a predetermined order. In the data array of the multi-channel PCM audio signal, data of each channel having the same sampling time is divided;
At least one synchronization code is added to separate the L and R channels or reproduce the clock signal on the receiving side. Further, as the synchronization code, a unique code which cannot occur in a normal audio signal between at least two or more pieces of sampled data adjacent on a sampling time is used. On the receiving side, the synchronization code is detected from the received data, and data of each channel is divided from the synchronization signal, L and R channels are separated, and a clock signal necessary for data recovery is reproduced. Further, at least one of a stereo signal and a monaural signal is used as the PCM audio signal used in the transmission method.

[0008]

FIG. 1 shows a configuration of an embodiment of the present invention, which will be described below. On the transmitting side, there are three types of A / D converters 21 _{1 to} 21 ₃ , and each A / D converter is supplied with an LR clock signal and a serial clock signal. Here, in the A / D converter 21 ₁ , the input L1 and R1 audio signals are sent to the PCM 1, and in the A / D converter 21 ₂ , the input L2 and R2 audio signals are sent to the PCM 2 and the A / D converter in 21 _3, the input L3, R3 audio signal to PCM3, respectively, to digital signal conversion. A / D converters 21 ₁ to 2
PCM signal output from the 1 ₃ is supplied to the division multiplexer 25 time. The time division multiplexer 25 has an LR clock,
A serial clock signal and other auxiliary information such as an AUX signal and a synchronization signal are supplied. These signals are time-division multiplexed and transmitted as one multi-channel PCM signal through one cable. On the receiving side, the transmitted multi-channel PCM signal is received by the time-division separator 26, and the LR clock and the serial clock signal are reproduced based on the received synchronization signal.
Sent to _{1-24 3.} Here, the D / A converter 24 to ₁ PCM1 is, is PCM2 the D / A converter 24 _2, D /
The A converter 24 ₃ is supplied PCM3, L1 is reproduced from the D / A converter 24 _1, R1 audio signal, is L2, R2 audio signal reproduced from the D / A converter 24 _2, D /
From A converter 24 ₃ is played L3, R3 audio signal is output. Further, from the time division separator 26, other additional information AUX signals and synchronization signals are also extracted.

Next, the operation of the present invention will be described with reference to the operation waveform diagram of FIG. Here, the sampling frequency is, for example,
Assuming 48 KHz, the LR clock signal is 48 KHz
Becomes The positive side of the LR clock signal is the L channel, and the negative side is the R channel. If the frequency of the serial clock is 6.144 MHz, the PCM data of the L channel at the sampling time n is output in period 1 which is the first half of the Ln period. Similarly, the PCM data of the R channel is output in period 2 which is the first half of the Rn period. The L channel of the sampling time n + 1 is output in period 3. As described above, various signals are multiplexed on the PCM multiplexed data. For example, the synchronization signal is used in the period 4 of the sampling time n, and the L1 is used in the period 5.
The audio PCM1 signal, the L2 audio PCM2 signal in period 6, the L3 audio PCM3 signal in period 7, and the AUX in period 8
Data signal, R1 voice PCM1 signal in period 9, R2 voice PCM2 signal in period 10, R3 voice PM1 signal in period 11
The CM3 signal, the synchronization signal in the period 12 of the sampling time n + 1, and the L1 audio PCM3 of the sampling time n + 1 in the period 13
The signal is repeatedly inserted. Here, the synchronizing signal does not normally occur in the audio signal every sampling time.
Two unique codes (synchronous code S1, synchronous code S2) are repeatedly inserted.

Hereinafter, the unique code of the synchronization signal will be described with reference to FIG. A / D analog audio signal
When converting into a digital signal by the converter, the digital signal shown in FIG.
(A binary code obtained by inverting the MSB) is generally used. In the case of 16-bit digital data, “0111111111111111” is the maximum value and “1000000000000”
00000 "is the minimum value. At the sampling time n shown in FIG. 2, the synchronization code S1 is inserted in the period 4 of the PCM multiplexed data, and this unique code is, for example," 0111111111111111 ".
And Also, at the sampling time n + 1, the synchronization code
S2 is inserted in the period 12 of the PCM multiplex data. If the unique code is, for example, "100000000000000000", the combination of the synchronization codes S1 and S2 becomes a combination of the unique codes.
Synchronous signal transmission is possible. The reason is that the voice transmission device has a necessary frequency band, and a signal in an unnecessary frequency band is cut off by the filter circuit. In other words, the sampling time n and the sampling time n + 1 are sampling points that are temporally adjacent to each other, and the high-frequency component in which the sampling value changes from the maximum value to the minimum value during that period is clearly determined by the filter circuit in the transmission line. The PCM signal that is in the region to be cut off and that changes in this way can be said to be a combination that cannot be generated by a normal audio signal.

Therefore, since this code combination is a unique code combination, it can be used to transmit a 24 KHz synchronization signal and reproduce the LR clock and the serial clock. The code values of the synchronization codes S1 and S2 are not only combinations of the maximum value and the minimum value, but also values near the combination are almost usable, and many combinations are possible.
Also, in period 8 of FIG. 2, 16-bit data is input,
It can be used for transmitting other additional information. The additional information includes information on the content of the audio signal, for example, information on signal processing such as emphasis. However, this data structure must not be similar to the synchronization code.

[0012]

As described above, according to the multi-channel stereo PCM audio transmission system of the present invention, it is possible to transmit a six-channel audio signal at a bit rate of 6.144 Mbps with one cable. For this reason, three cables are required as in the conventional AES / EBU transmission system, and transmission can be performed more efficiently as compared with a cable requiring a transmission bit rate of 6.144 Mbps.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of the present invention.

FIG. 2 is an operation waveform diagram of the present invention.

FIG. 3 is a diagram showing a signal level of a unique code used in the present invention.

FIG. 4 is a block diagram showing a configuration of a general PCM direct transmission system;

FIG. 5 is a block diagram showing a configuration of a general AES / EBU interface transmission system;

FIG. 6 is an operation waveform diagram of the PCM direct transmission system.

FIG. 7 is an operation waveform diagram of a transmission method using an AES / EBU interface.

FIG. 8 is a layout diagram of speakers of a multi-channel stereo.

[Explanation of symbols]

21 _{1 to} 21 ₃ : A / D converter, 24 _{1 to} 24 ₃ : D / A converter, 25: Time division multiplexer, 26: Time division separator, 1:
L channel PCM data transmission period of sampling time n,
2: R channel PCM data transmission period with sampling time n 3: L channel PCM data transmission period with sampling time n + 1 4: Synchronization code S1 transmission period 5: L1 channel PCM data transmission period 6: L2 channel PCM
Data transmission period, 7: L3 channel PCM data transmission period, 8: Other additional information transmission period, 9: R1 channel PCM data transmission period, 10: R2 channel PCM
Data transmission period, 11: R3 channel PCM data transmission period, 12: Synchronization code 2 transmission period, 13: L1 channel PCM data transmission period of sampling time n + 1.

Claims (5)

[Claims] 1. Pulse coded modulation (hereinafter referred to as PCM)
System digital multi-channel audio signal transmission,
The multi-channel PCM audio signal to be transmitted is time-divided into left (L) channel and right (R) channel signals at predetermined sampling times, and in the time domain of the L channel, the L channel signal of each channel is further divided. Are divided and arranged in a predetermined order, and in the time domain of the R channel, each R channel signal is divided and arranged in a predetermined order and transmitted. 2. The multi-channel P according to claim 1, wherein
In the data array of the CM audio signal, at least one of a synchronization code for dividing data of each channel having the same sampling time, dividing the L and R channels, or reproducing a clock signal on the receiving side is included. A multi-channel PCM audio signal transmission system characterized by being added. 3. The method according to claim 2, wherein a unique code that cannot occur in a normal audio signal between at least two or more sampled data adjacent on a sampling time is used as the synchronization code. Multi-channel PCM audio signal transmission system. 4. The receiving device according to claim 2, wherein the receiving side detects the synchronization code from the received data, and separates the data of each channel, the L and R channels, and restores each data from the synchronization signal. A multi-channel PCM audio signal transmission system for reproducing a clock signal. 5. The multi-channel PCM audio signal transmission system according to claim 1, wherein at least one of a stereo signal and a monaural signal is used as the PCM audio signal used in the transmission system.