JPH01291584A - Voice transmission system - Google Patents

Abstract

PURPOSE:To enable a voice signal to be inserted by using the remaining part of information suppressed by a DPCM signal of (n-1) bits by converting part of the vertical synchronizing section of an analog picture signal to the DPCM signal of (n-1) bits and the remaining part of it to the DPCM signal of (n) bits. CONSTITUTION:A digital picture signal (b) is inputted to DPCM conversion parts 3 and 4, and is converted to the DPCM signal of five bits and the DPCM signal of four bits, respectively. A synchronizing signal (c) resets the DPCM conversion parts 3 and 4, and also, is inputted to a voice multiplexing part 5 and a signal control part 6. In the voice multiplexing part 5, the multiplexing of the synchronizing signal (c) and the voice signal (f) is performed. In the signal control part 6, a control signal for the voice multiplexing part 5 according to the synchronizing signal (c) and a signal selection part 7 is generated, and is outputted as the control signal (g). Part of the digital picture signal (b) of the vertical synchronizing section t 3 is converted to the DPCM signal 15 of four bits according to the control signal (g), and the voice signal 14 of a channel 2 as the information unmultiplexed at the section t 2 of the vertical synchronizing section is multiplexed by using a remaining one bit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a system for converting an analog image signal into a digital image signal, multiplexing a digital audio signal on the digital image signal, and transmitting the multiplexed signal.

[Conventional technology]

In conventional technology, when an analog image signal is converted into a digital image signal and a digital audio signal is multiplexed with this digital image signal for transmission, the output of converting the digital image signal into an n-bit fixed length differential code and the analog A digital audio signal was multiplexed and transmitted in the horizontal synchronization signal section separated from the image signal (Special Publication No. 57-31277).
(see publication).

[Problem to be solved by the invention]

In the conventional method described above, an analog image signal is converted into a digital n-bit fixed-length differential code, and in order to multiplex a digital audio signal into the horizontal synchronization signal section of the digital image signal, the period is shorter than the horizontal synchronization signal section. There is a drawback that the amount of information of the digital audio signal that can be multiplexed is limited in the vertical synchronization signal section.

[Means to solve the problem]

In order to eliminate such drawbacks, the audio transmission system according to the present invention includes an A/D converter that converts an analog image signal into a digital image signal, and a synchronization separation unit that separates a horizontal synchronization signal and a vertical synchronization signal from the analog image signal. an n-bit DPCM converter that converts the digital image signal converted by the A/D converter into a predetermined n-bit fixed-length differential code;
The digital image signal converted by the A/D converter is (n
-1) Convert to bit fixed length differential code (n -1)
It has a bit DPCM conversion section and a signal control section that generates a control signal from the horizontal synchronization signal and vertical synchronization signal separated by the synchronization separation section. The vertical synchronization signal is multiplexed with the output of the n-bit DPCM conversion unit or the output of the (n-1) bit DPCM conversion unit and a digital audio signal. It is. 1 (Operation) In the audio transmission system according to the present invention, the audio signal is converted into an (n - 1) bit DPCM (C differential PCM) signal, and the audio signal is inserted into the remaining part of the information suppressed in a part of the vertical synchronization interval. Ru.

〔Example〕

FIG. 1 is a system diagram showing an embodiment of the audio transmission system according to the present invention. In the figure, 1 is an A/D conversion section, 2 is a synchronization separation section, 3 and 4 are DPCM conversion sections, 5 is an audio multiplexing section, 6 is a signal control section, and 7 is a signal selection section.

This embodiment will be explained assuming that the DPCM converter 3 is 5 bits, the DPCM converter 4 is 4 bits, the digital audio to be multiplexed is 3QkHz, and the audio is 2 channels with 12 bits per sample. Note that the present invention is not limited to this.

The analog image signal a is input to the A/D converter 1 and the sync separator 2, and the A/D converter 1 converts it into a digital image signal, outputs this digital image signal, and then sends it to the sync separator 2.
Then, detect the horizontal synchronization signal and vertical synchronization signal, and detect the synchronization signal C.
Output as .

The timings of the analog image signal a and the synchronization signal C are shown in Figure 2 (al) and (bl). In Figure 2 (a), tl
is the period of the horizontal synchronization signal, t2 is the period of the vertical synchronization signal, t
3 is a vertical synchronization period.

The digital image signal is input to the DPCM converter 3.4, which converts the 5-bit DPCM signal and the 4-bit DPCM signal into each other.
It is converted into a PCM signal.

The synchronization signal C resets the DPCM conversion section 3 and the DPCM conversion section 4, and is inputted to the audio multiplexing section 5 and the signal control section 6. The audio multiplexing section 5 multiplexes the synchronization signal C and the audio signal f. In the signal control section 6, a control signal for the audio multiplexing section 5 and the signal selection section 7 is generated in accordance with the synchronization signal C, and outputted as a control signal g.

The timing of the control signal g and the multiplexing format of the audio multiplexer 5 are shown in FIGS. 2C and 2C. Normally, except for the vertical synchronization period t3, the digital image signal is converted into a DPCM signal (5 bits), and in the horizontal synchronization signal period t1, a unique word 11 indicating the start of synchronization and a reset value 12 indicating the level of the synchronization signal are used for two channels. 13 and 14 are multiplexed. In the vertical synchronization period t3, the vertical synchronization signal period t
2 is approximately 1/2 of the period t1 of the horizontal synchronization signal, so in the same format as audio is multiplexed in the period of the horizontal synchronization signal, only 1/2 of the information can be multiplexed in the period t2 of the vertical synchronization signal. Therefore, according to the control signal g, a part of the digital image signal in the vertical synchronization period t3 is converted into a 4-bit DPCM signal 15, and the remaining 1 bit is used to convert the digital image signal in the vertical synchronization signal period t2 as information that cannot be multiplexed. The audio signal 14 of channel 2 is multiplexed. The audio multiplexing format for the horizontal synchronization signal section t1 and the audio multiplexing format for the horizontal synchronization section t3 are
As shown in the figure.

In the signal selection section 7, the DPCM conversion section 3 selects 5 bits)
The audio multiplexing unit 5 multiplexes two channels of audio signals into the horizontal synchronization signal section t2 or multiplexes one channel's worth of audio signals into the vertical synchronization signal section on the image signal converted to the DPCM signal. selects the multiplexed signal d obtained by the DPCM converter 4 and the multiplexed signal e obtained by multiplexing the audio signal of the remaining one channel onto the image signal converted into a 4-pill DPCM signal by the DPCM converter 4, according to the control signal g;
Output as a transmission signal.

〔Effect of the invention〕

As explained above, the audio transmission system according to the present invention transmits a part of the vertical synchronization period of an analog image signal (n-1)
DPCM signal, by converting the remaining part of the above vertical synchronization period to an (n-pi) DPCM signal, respectively.
1) There is an effect that an audio signal can be inserted using the remaining part of the information suppressed in a part of the vertical synchronization period converted into a bit DPCM signal.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the audio transmission system according to the present invention, and FIG. 2 is a time chart for explaining its operation. DESCRIPTION OF SYMBOLS 1... A/D conversion part, 2... Synchronization separation part, 3, 4.
...DPCM converter, 5...audio multiplexer, 6...
Signal control section, 7... signal selection section. Patent applicant: NEC Corporation Miyagi NEC Corporation

Claims (1)

[Claims] A/D that converts analog image signals to digital image signals
a converter, a synchronization separator that separates a horizontal synchronization signal and a vertical synchronization signal from the analog image signal, and a synchronization separator that converts the digital image signal converted by the A/D converter into a predetermined n-bit fixed-length differential code. a bit DPCM conversion unit;
The digital image signal converted by the A/D converter is converted into a fixed length differential code of (n-1) bits (n-1).
) bit DPCM conversion unit, and a signal control unit that generates a control signal from the horizontal synchronization signal and vertical synchronization signal separated by the synchronization separation unit, and the control signal causes the horizontal synchronization signal to contain digital audio. signal and the n-bit DP
The output of the n-bit DPCM converter or the (n-
1) An audio transmission system characterized by multiplexing the output of a bit DPCM converter and a digital audio signal.