JPS5961286A - Sound multiplexing system - Google Patents

Abstract

PURPOSE:To multiplex a sound signal to a picture signal, by displaying the existence of the sound signal by using the uppermost bit, multiplexing the sound signal to the picture signal, and on the receiving side, discriminating the code indicating the existence of the sound signal to separate the sound signal. CONSTITUTION:On the transmitting side, an analog sound signal (b) applied to an input terminal 2 is converted into a digital signal (h) by an A/D converter 4 and the digital signal (h) is applied to a parallel/series converting circuit 9. The circuit 9 applies a signal (k) obtained by converting the digital sound signal into a series signal to a multiplexing circuit 11, which inverts the uppermost bit of the shortest code and adds the sound signal to the shortest code to multiplex the signals. On the receiving side, a multiplexed signal (n) applied to an input terminal 21 is added to a variable length decoding circuit 22 and a detecting circuit 23 and the circuit 23 detects a signal ''0111'' indicating the existence of the sound signal from the multiplexed signal (n). A separating circuit 24 can separate the sound signal following the signal ''0111'' obtained before decoding. Consequently, the sound signal can be multiplexed to the picture signal without constituting a frame.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an audio multiplexing method for multiplexing and transmitting an audio signal converted into a digital signal onto a TV signal or other image signal converted into a digital signal.

Prior Art and Problems Conventionally, when an audio signal is multiplexed onto an image signal and transmitted, it has generally been a frame configuration. That is, as shown in FIG. 1, one frame i is composed of a synchronization signal F indicating the beginning of the frame, an audio signal S, and an image signal VD, and the audio signal S is slower than the M signal VD. Therefore, a small number of bits are allocated.

On the receiving side, the synchronization signal F is detected and synchronized, and the audio signal S that follows the synchronization signal F and the image signal VD that follows it are separated. Therefore, a circuit for identifying the beginning of a frame by detecting the synchronization signal F and a memory for separating the audio signal S from the image signal VD are required, which has the drawback of increasing the circuit scale on the transmitting side and the receiving side.

OBJECTS OF THE INVENTION It is an object of the present invention to make it possible to multiplex an audio signal with an image signal and transmit the multiplexed image signal without requiring a frame structure. Examples will be described in detail below.

Embodiment of the Invention Fig. 2 is a block diagram of the main part of the transmitting side of the embodiment of the invention, where ■ is an input terminal for an image signal, 2 is an input terminal for an audio signal, and 3.4 is a block diagram for converting an analog signal into a digital signal. A to convert
D converter, 5 is a clock generator, 6 is a differential encoding circuit,
7 is a variable length encoding circuit; 8 is a frequency dividing circuit; 9 is a parallel-to-serial conversion circuit; 10 is a timing generation circuit that generates an insertion timing signal for audio signals; 11 is a multiplexing circuit; and 12 is an output terminal for multiplexed signals. It is. This embodiment is a case where an image signal is differentially encoded and a variable encoding method is adopted in which the length of the code is changed depending on the probability of occurrence.

The clock generator 5 generates a clock C having a frequency of, for example, 10 MHz, and the frequency divider circuit 8 divides the frequency of the clock to generate a clock d of 10 KHz, for example. That is, the clock generator 5 generates a clock at the sampling frequency of the image signal applied to the input terminal 1, which is used as a clock at the sampling frequency of the audio signal applied to the input terminal 2 by the frequency dividing circuit 8.

Of course, it is also possible to frequency-divide the output of the clock generator 5 to obtain a clock having a desired sampling frequency of the image signal.

The analog image signal a is sent to the clock C by the AD converter 3.
The digital signal e is sampled and converted into a digital signal e, which is applied to the differential encoding circuit 6. This differential encoding circuit 6 outputs a code signal f obtained by quantizing the difference value of the digital signal e, and applies it to the variable length encoding circuit 7. Due to the nature of the image signal, the difference values of the digitized image signal are distributed around 0, as shown in FIG. Quantize this to find 0, which has the highest probability of occurrence.
By assigning the shortest code to the value near {=J and sequentially assigning longer codes, the amount of transmission can be reduced, and is already known as a band compression means in digital transmission of GoV signals. This is a method that

In Figure 3, the quantized signal A with a difference value near 0 has a 2-bit 1. “Ol”, the next quantized signal B with a larger difference value has a 3-bit “001”, and the next quantized signal This shows a case where 4 bits of "0001" are assigned to the conversion signal C, and 5 bits of "0000bi" are assigned to the next conversion signal D. The variable length encoding circuit 7 performs the operation of converting into such a variable length code, and can be easily implemented using a known configuration. The variable length code signal g converted by the variable length encoding circuit 7 is applied to the multiplexing circuit 11.

In this embodiment, the two most significant bits of the shortest code are used as bits indicating whether or not an audio signal is inserted. For example, "01" indicates no audio signal, and "1" indicates no audio signal.
In the case of "1", it is assumed that an audio signal is present, and the most significant bit is controlled in the multiplexing circuit 11 based on the audio signal insertion timing signal p from the timing generating circuit 10.

The analog audio signal b added to the human power terminal 2 is 81
] The signal is sampled by the converter 4 at fL'>1 on the clock d, and converted into a digital signal h, which is then applied to the parallel-serial conversion circuit 9. Since the divided output clock d of the frequency dividing circuit 8 is applied to the AD converter 4 and the timing generation circuit 10, the timing generation circuit 10 can output the audio signal insertion timing signal l.
This timing signal l is applied to the parallel-to-serial conversion circuit 9 and the multiplexing circuit 11, and from the variable length encoding circuit 7, the timing signal i is generated when the shortest code information, ie, 2 bits 1 when variable length encoded, is 1. Since it is added to the circuit 10,
When the shortest code information near the audio signal insertion timing is added, the timing signal p. j is added to the multiplexing circuit 11 and the parallel-to-serial conversion circuit 9. As a result, the parallel-to-serial conversion circuit 9 converts the digital audio signal into a serial signal k.
is added to the multiplexing circuit 11, the multiplexing circuit 11 inverts the most significant bit of the shortest code, adds an audio signal next to the shortest code, and multiplexes the signal. The multiplexed signal m is sent out from the output terminal 12. Digital audio signal is 1 bit 1
- It is possible to multiplex the data to multiple destinations or to multiplex the data to multiple sites, and has a predetermined fixed length of bits.

FIG. 4 is an explanatory diagram of the above-mentioned operation, in which the insertion period of the audio signal is shown by ], and 1 bit of the audio signal is not shown. That is, the shortest code for each cycle 'F is set to "11", and the audio signal V is inserted and multiplexed. In this case, the shortest code may not occur exactly every period T, but since the speed of the image signal is about iooo times faster than the audio signal as mentioned above, even if there is a shift in multiple codes, it is actually This is not a problem.

Note that since the probability of occurrence of the shortest code is high, it is possible to insert an audio signal approximately every cycle T.

When the code shown in FIG. 4 is converted into serial data, it becomes as shown in FIG. 5, and the image signal is 2 bits, 3 bits, 4 bits, etc. Code identification is possible by sequentially dividing 5 bits, and by dividing 4 bits, "0 1 1 1
''', it can be identified that the code "l l" indicates the presence of an audio signal, so it is easy to know that the next code is an audio signal.In other words, on the receiving side, "
It is sufficient to monitor the four bits of "0111" and, when those four bits are detected, process the next bit as an audio signal.

FIG. 6 is a block diagram of the main parts of the receiving side of the embodiment of the present invention, in which 21 is an input terminal for a multiplexed signal, 22 is a variable length decoding circuit, 23 is a detection circuit for detecting a code into which an audio signal is inserted; 24 is a separation circuit that separates the audio signal from the image signal;
5 ba 1 tomo circuit, 26 is an I] Δ converter that converts a digital signal to an analog signal, 27 is a serial-parallel converter circuit, 2
1 is a DA converter for converting a digital signal into an analog signal, 29 is an output terminal for an image signal, and 30 is an output terminal for an audio signal. The multiplexed signal n applied to the input terminal 21 is applied to the variable length decoding circuit 22 and the detection circuit 23, and the detection circuit 23 detects "Ol11" from the multiplexed signal n, and the detection signal 0 is variable. It is added to the long decoding circuit 22. This variable length decoding circuit 22 decodes the multiplexed signal n into a differential code signal p, and detects the detection signal 0.
Since the next code is an audio signal, it is added to the separation circuit 24 without being decoded.

The variable length decoding circuit 22 also applies a signal q indicating the code length of the decoded differential code to the separation circuit 24.

The separation circuit 24 separates the image signal r and the audio signal S from the differential code signal p output from the variable length decoding circuit 22.
From the detection signal 0 and code length signals q and 6, “'O” before decoding
The audio signal after l1bi can be separated. Since the separated image signal r is a differential code signal, the decoding circuit 25
is decoded into a digital signal t, which is sent to the DA converter 26
The signal is converted to an analog image signal U and output to terminal 2.
It is output from 9. The divided audio signal S is converted into a parallel signal V by the serial/parallel conversion circuit 27, and 1]A
It is converted into an analog audio signal W by the converter 28 and output from the output terminal 30.

As described above, on the receiving side, the audio signal can be easily separated from the multiplexed signal n using the code indicating whether or not the audio signal is inserted. In addition, although the above-mentioned embodiment is a case where variable encoding is used to create a transmission path code, when an image signal is encoded into a fixed-length code number and transmitted, the fixed-length code can also be used. The most significant bit of the code is used to indicate whether or not an audio signal is to be inserted, and the audio signal can be inserted.

Effects of the Invention As explained above, the present invention, when converting an image signal into a transmission line code, uses the most significant bit to indicate whether or not an audio signal is inserted, and multiplexes the audio signal with the image signal. On the receiving side, the audio signal can be separated by identifying the code with the insertion of the audio signal. Therefore, the audio signal can be multiplexed on the image signal without using a frame configuration. In particular, when transmitting image signals using variable-length encoding, it is possible to add an audio signal to the shortest code and multiplex it, so the shortest code can be used as a code that indicates whether or not an audio signal is inserted, making it easy for the receiving side to transmit the image signal. The audio signal can be separated into Therefore, the synchronization bit required for frame synchronization becomes unnecessary, and transmission efficiency can be improved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the frame structure of a conventional example in which an audio signal is multiplexed with an image signal, Fig. 2 is a block diagram of the main part of the transmitting side of an embodiment of the present invention, and Fig. 3 is a difference value and its probability of occurrence. FIG. 4 is an explanatory diagram of the variable encoding signal of the image signal and the insertion position of the audio signal, FIG. 5 is an explanatory diagram showing the codes shown in FIG. 4 converted into serial, FIG. 6 is a block diagram of the main parts of the receiving side according to the embodiment of the present invention. 1 is an input terminal for image signals, 2 is an input terminal for audio signals, 3
．． 4 is an AD converter, 5 is a clock generator, 6 is a differential encoding circuit, 7 is a variable length encoding circuit, 8 is a frequency dividing circuit, 9 is a parallel-to-serial conversion circuit, and 10 is an audio signal insertion timing signal. I1 is a multiplexing circuit,
12 is an output terminal for a multiplexed signal, 21 is an input terminal for a multiplexed signal, 22 is a variable length decoding circuit, 23 is a detection circuit that detects a code into which an audio signal is inserted, and 24 is a separation unit that separates an audio signal from an image signal. circuit, 25 is a decoding circuit, 26 is a DA converter, 27 is a serial/parallel converter circuit, 28 is a DA converter, 2
9 is an output terminal for image signals, and 30 is an output terminal for audio signals. -489-1

Claims (1)

[Claims] In an audio multiplexing method that multiplexes an audio signal converted into a digital signal with an image signal converted into a digital signal,
When converting the image signal into a transmission line code, the most significant bit is inverted for each plurality of transmission line codes to create a code indicating the presence of insertion of an audio signal, and the audio signal is inserted and multiplexed after the code, On the receiving side, the code indicating that an audio signal has been inserted is identified and the audio signal inserted after the code is detected. /7)!
An audio multiplexing method characterized by