JPH03289231A - Time division multiplex transmission system - Google Patents

Abstract

PURPOSE:To minimize the change in the system by using a prescribed high-order bit not contributing to signal coding, applying time division to a data signal other than a composite video signal and sending the signal. CONSTITUTION:Since various signals sent for horizontal and vertical blanking periods in a composite video signal reach a prescribed level depending on the kind of signal, several bits from the MSB are not used for coding for the horizontal and vertical blanking periods when the composite video signal is subject to linear coding by the PCM code or the like. Then bits not in use are utilized to use the data such as voice signal for the transmission. That is, the data signal such as the voice signal is multiplexed digitally to a part without information substantially in the digital composite video signal to be coded. Thus, no processing is applied to the original video signal data and the revision in the system is minimized.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) With the development of new media such as video telephones and cable visitors (CATV), or for relaying television signals, video signals and Optical transmission of audio signals has become common practice.

Conventionally, when a video signal and an audio signal are linearly encoded by PCN encoding or the like and then optically transmitted, the process is as shown in FIG. That is, the video signal is encoded as a composite signal including a synchronization signal with a quantization bit number of 8 to 10 bits. The sampling frequency associated with video signal quantization is often synchronized with the horizontal synchronization signal or color subcarrier signal of the video signal in order to eliminate the occurrence of beat noise.

This is so-called lock coding. Additionally, audio signals are generally sampled at a frequency synchronized with the transmission link and digitized. The digitized video and audio signals obtained in this way are each subjected to time-base compression, and as shown in FIG. 5, are time-division multiplexed with a transmission line frame added thereto.

FIG. 5 shows only a schematic frame structure; in reality, the frame structure is more complicated than the one shown because transmission path coding is performed or a multi-frame structure is used.

If the transmission lock and the video sampling frequency are not synchronized, they are synchronized by stuffing and then multiplexed.

(Issue 11 to be solved by the invention) When optically transmitting a video signal and an audio signal, the video signal and the audio signal are each sampled and digitized using clocks with different sampling frequencies, and each is digitized on a time axis. After compressing, the data is time-division multiplexed and transmitted with transmission path frames added.

In other words, in order to eliminate the occurrence of beat noise in the video signal,
Sampling is performed in synchronization with the horizontal synchronization signal of the video signal, and audio signals are sampled at a frequency synchronized with the transmission lock. Also, since video signals have a larger amount of information than audio signals, they are sampled at a higher sampling frequency to obtain higher resolution, and audio signals have less information than video signals, so they are sampled at a lower sampling frequency. . Then, of one horizontal synchronization period of the video signal including the horizontal synchronization signal, the generation section of the horizontal synchronization signal is allocated to the data transmission of the audio signal, and the remaining section is used for the data transmission of the video signal.

In this way, since the video signal and audio signal are handled independently, it is necessary to provide an area in addition to the video signal to multiplex the audio signal separately, which not only complicates the frame structure but also increases the In a system that is configured to transmit only signals, if you want to add and transmit audio signals, you will have to create a new transmission format, which will require major changes to the system. was there.

In addition, in recent years, audio multiplex broadcasting, stereo broadcasting, etc. are being carried out, but when transmitting audio signals for multiple channels, it is necessary to use a frame structure that transmits audio signals for one audio channel. In the system, new transmission formats must be constructed as well.

In other words, when transmitting video signals using conventional methods,
Increasing the number of audio signal channels requires major system changes and has the disadvantage of lack of flexibility.

Therefore, an object of the present invention is to enable data signals other than video signals such as audio signals to be added and transmitted without changing the transmission format even in a system that transmits only video signals. Therefore, it is an object of the present invention to provide a time division multiplex transmission system that can minimize system changes.

[Configuration of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention is configured as follows. That is, in a transmission method that multiplexes and transmits a composite video signal and a data signal other than the video signal, the composite video signal is linearly encoded, and the horizontal synchronization signal part excluding the vertical synchronization signal part, the horizontal retrace interval, or the vertical The present invention is characterized in that data signals other than the composite video signal are time-division multiplexed using predetermined upper bits that do not contribute to the encoding of the signal among the encoded bits of the signal in the retrace interval, and are transmitted.

(Function) In the composite video signal, in the horizontal and vertical blanking sections, the various signals sent to these sections have a constant level determined depending on the signal type. Therefore, when a composite video signal is linearly encoded using a PCM code or the like, several bits from the MSB are not used for encoding in the horizontal and vertical blanking sections. Therefore, the present invention utilizes these unused bits to transmit data such as voice. That is, a data signal such as audio is digitally multiplexed onto a portion of the encoded digital composite video signal that has substantially no information.

In this method, the composite video signal is synchronized with a video synchronization signal and linearly encoded, and the code of the signal is determined from among the encoded bits of the horizontal synchronization signal portion other than the vertical synchronization signal, the horizontal retrace interval, or the vertical retrace interval. Data signals other than the composite video signal are time-division multiplexed and transmitted using predetermined upper bits that do not contribute to the image processing.

In this way, when a composite video signal is encoded, information such as audio signals is multiplexed and transmitted by taking advantage of the fact that several bits from the MSB are not used for encoding in the horizontal and vertical blanking sections. do.

In the present invention, when a composite video signal is encoded, information such as an audio signal is multiplexed and transmitted using bits that are not used for encoding, so there is no trace of the original video signal data. Therefore, signal processing can be done easily, system changes can be kept to a minimum, and even digital transmission lines with a transmission capacity of only one channel of video signals can be used. , it becomes possible to multiplex and transmit data signals such as audio signals.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. First, the present invention will be explained in detail.

The present invention makes it possible to transmit many audio channels without changing the transmission format by digitally multiplexing an audio signal onto a portion of an encoded digital video signal that does not substantially have video information. It is something to do.

The principle will be explained using FIG.

FIG. 3 is a diagram showing a composite video signal and how it is encoded. As shown in FIG. 3(a), horizontal blanking sections 32 between video signals 31 (adjacent fields) of the composite video signal The area before the generation position of the horizontal synchronizing signal 34 is a front porch 83, and the area after it is a back porch 85, and has a configuration as shown in this figure.

In the area of back porch 35, color burst signal 3B
is generated.

As can be seen from the figure, the video signal 31 does not exist within the horizontal blanking section 32, and the signal level is a fixed value. FIG. 3(b) is a diagram showing data obtained by quantizing this composite video signal. Among the quantized bits schematically shown here, the black parts in the diagram are effective quantized bits, and the MSB ( The white part near the most significant bit (most significant bit) indicates bits that are not used for quantization, that is, bits that have no information.

Quantization is 140 IRE (sync signal level 40 I
R.E.

Video signal level 100 IRE) 10 overload level (2
This is generally done with a maximum width of 0 to 40 IRE). The level of the front porch 33 and back porch 35 is 4 if the maximum level of quantization is 1601RE.
0/160, and bits other than the MSB are used for quantization. On the other hand, if the maximum level of quantization is 180 IRE, it becomes 407180, and the (MSB-1) bit also becomes a bit with no information.

Also, the peak level of color burst signal 3B is 607
180, and bits other than the MSB are used for quantization. The level of the horizontal synchronization signal 34 is basically the minimum level, but it is not zero level, so the number of effective bits is the number of quantization bits minus about 5 bits.

Therefore, about 5 bits are bits without information.

As explained above, each signal level in the horizontal blanking section 32 is constant, and the white part of the quantized bits in FIG. 3(b) has no video information, so this area is used for data transmission. If used properly, it is possible to multiplex and transmit audio signals and the like in the video signal transmission area.

Although the horizontal synchronization signal 34 is generated periodically, as shown in FIG. 4, during the vertical blanking period 32, information such as an audio signal cannot be placed on the 5 bits of the vertical synchronization signal. However, since there are many parts in the vertical blanking interval where there is no video signal, it is possible to use this part to transmit information using the MSB 1 bit or 2 bits.

The configuration of a transmission system that transmits data using such a principle will be described next.

FIG. 1 shows a block diagram of the countries in which the blocks of the transmitter in an embodiment of the present invention are constituted, and FIG. 2 shows a block diagram of an example of the structure of the receiver.

In the figure, reference numeral 1 denotes a video encoding circuit, which encodes an input composite video signal in PCM and outputs it. Reference numeral 2 denotes a synchronization signal generation circuit, which generates various synchronization signals and clocks based on the input video signal.

3 is an audio encoding circuit 3, which converts the input audio signal into P
It is CM coded and output.

Reference numeral 4 denotes a video/audio multiplexing circuit which receives the outputs of the video encoding circuit 1 and the audio encoding circuit 3 and multiplexes them. is time-division multiplexed and output.

5 is a transmission path encoding circuit which converts the output of the video/audio multiplexing circuit 4 including the frame signal from the frame generation circuit 6;
This is a circuit that encodes and outputs.

The transmission path frame generation circuit 6 is a circuit that generates a frame signal indicating the position where audio signals are multiplexed, and generates the frame signal based on the output of the synchronization signal generation circuit 2. Reference numeral 7 denotes an electrical-optical conversion circuit, which converts an electrical signal into an optical signal and sends it to the transmission line. The above is an example of the configuration of the transmitter.

Next, the configuration of the receiving section will be explained. In FIG. 2, 8 is an optical receiving circuit (optical-electrical conversion circuit), which is a circuit that converts a transmitted optical signal into an electrical signal. Reference numeral 9 denotes a transmission line decoding circuit, which decodes the electrical signal received and output by the optical receiving circuit 8 into the original video/audio multiplexed signal.

IO is a transmission line frame synchronization circuit, which generates a frame signal necessary for decoding based on the electrical signal received and output by the optical receiving circuit 8. Reference numeral 12 denotes a video/audio frame synchronization circuit, which generates frame signals and various clocks necessary for separating the video/audio multiplexed signal output from the transmission path decoding circuit 9 into the original composite video signal data and audio signal data. be.

Reference numeral 11 denotes a video/audio separation circuit, which separates the output of the transmission path decoding circuit 9 into a digital video signal and a digital audio signal based on the frame signal output from the video/audio frame synchronization circuit 12.

Reference numeral 13 denotes a video decoding circuit, which demodulates the digital video signal output from the video and audio separation circuit 11 into the original composite video signal based on the frame signal output from the video and audio frame synchronization circuit 12, and outputs the demodulated signal. be. Reference numeral 14 denotes an audio decoding circuit, which demodulates the digital audio signal output from the video/audio separation circuit 1t into the original analog audio signal based on the frame signal output from the video/audio frame synchronization circuit 12, and outputs the demodulated signal. be. The above is an example of the configuration of the receiving section.

The operation of this device having such a configuration will be explained.

First, the operation of the transmission system will be explained.

In this apparatus, an input composite video signal is PCM encoded by a video encoding circuit 1. At the same time, the input composite video signal is also given to a synchronization signal generation circuit 2, which generates various synchronization signals and clocks based on the input composite video signal in order to perform lock coding.

On the other hand, the input audio signal is PCM coded by the audio encoding circuit 3 which operates in synchronization with the synchronization signal output from the synchronization signal generation circuit 2. The audio signal may be a signal of multiple channels as long as the amount of information is commensurate with the capacity to be multiplexed.

The outputs of the video encoding circuit 1 and the audio encoding circuit 3 are sent to the video/audio multiplexing circuit 4, where the audio signal is time-division multiplexed onto a portion of the vertical and horizontal retrace sections of the video signal. The multiplexing method in this video/audio multiplexing circuit 4 will be described in detail separately.

Next, the signal that is time-division multiplexed and output by the video/audio multiplexing circuit 4 is sent to the transmission line encoding circuit 5, where it is converted into a code suitable for transmission, and is further converted into an electric-to-optical converter circuit 7.
The signal is converted into an optical signal and then output to the transmission line. still,
Although optical transmission has been explained here as an example, optical transmission or wireless transmission may also be used.

Next, the operation of the receiving system will be explained. The transmitted optical signal is regenerated into an electrical signal by an optical-to-electrical conversion circuit 8, and decoded into an original video/audio multiplexed signal by a transmission line decoding circuit 9. A frame signal necessary for decoding is generated in a transmission line frame synchronization circuit IO. The video/audio separation circuit 11 uses the frame signal and various clock signals output from the video/audio frame synchronization circuit 12 to separate the signal from the transmission line decoding circuit 9 into a digital composite video signal and a digital audio signal.

Of the separated signals, the digital composite video signal is sent to the video decoding circuit 13, where the portion of the digital composite video signal where the audio signal was written is rewritten to zero data and then video decoded. The signal is sent to the circuit 13.

Various signals necessary for operations such as data separation and rewriting are generated by the video/audio frame synchronization circuit t2.

Further, the digital video signal output from the video/audio separation circuit 11 is demodulated into the original composite video signal by the video decoding circuit 13, and output as the composite video signal.

On the other hand, the digital audio signal separated and outputted by the video/audio separation circuit 11 is demodulated into the original analog audio signal by the audio decoding circuit 14 and output as an audio signal.

Next, two embodiments of the multiplexing method of the video/audio multiplexing circuit 4 will be described.

The first example is a method of transmitting an audio signal using the MSB 1 bit of the horizontal blanking period, and in this method, the audio signal is written to the MSB 1 bit at the same repetition period in the vertical blanking period.

The sampling frequency of the video signal is four times the color subcarrier frequency in the NTSC composite video signal, and the sampling frequency of the audio signal is 48kHz.
, the number of quantization bits is 16 bits. Also, NTS
In method C, the horizontal blanking interval is 1019 μs and one line is 63.6 μs, so if the number of audio channels that can be secured is n, then 48X 103X 16X n < 3.
58X 106X 4X (10,9/ 63.8)
... (() is obtained, and as a result, n < 3.20, it is possible to secure high-quality audio signals for about three channels, and therefore, it is possible to transmit audio signals for these channels.

In the second example, an audio signal is transmitted using 5 bits of the horizontal synchronizing signal portion, and no audio data is carried in the vertical blanking section. One frame is 334m5. Vertical blanking interval is 2.2 @s diameter horizontal synchronization signal is 4.5
Since it is about μs, the number n of voice channels that can be transmitted is estimated as follows: 48XlO' x 16X n <3.58X10' x
4 X (4,5/e3.6) x ((3a, 3-2
．． 2) /:ls, 3) x 5...From the relationship (2), n < 6.16, and it can be seen that there is a capacity for transmitting high-quality audio signals through about 6 channels. In this method, since audio signals are not multiplexed in the vertical blanking section, it is necessary to block this section, making the demultiplexing method more complicated than in the first example.

To separate audio signals, it is necessary to transmit a frame signal indicating the multiplexed position on the transmitting side, and this signal is generally transmitted in addition to the audio data, but it is necessary to transmit a frame signal that indicates the multiplexed position. In order to use it, it is possible to transmit a frame signal by forcibly causing a code rule violation of the transmission line code.

That is, by forcibly generating a coding rule violation of the transmission line code at a position where a frame signal indicating the position where audio signals are multiplexed is generated, and processing the position where this coding rule violation occurs as a frame signal position, Even the position of the frame signal can be used as the audio data transmission area.

Note that these frame signal addition processes are performed by the transmission line encoding circuit 5 based on the output of the transmission line frame generation circuit 6.

As explained above, in the horizontal and vertical blanking sections of a composite video signal, the various signals sent to these sections have a constant level determined depending on the signal type, and such a composite video signal can be processed using PCM encoding, etc. When linear encoding is performed, several bits from the MSB are not used for encoding in the horizontal and vertical blanking sections. Focusing on this point, we use the bits that are not used for encoding and Since information such as audio signals is multiplexed and transmitted, there is no need to make any changes to the original video signal data, which simplifies signal processing and minimizes system changes. Furthermore, even on a digital transmission line that has a transmission capacity of only one channel of video signals, it becomes possible to multiplex and transmit data signals such as audio signals.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications within the scope of the gist thereof.

[Effects of the Invention] As explained above, the present invention takes advantage of the fact that when a composite video signal is PCM encoded, several bits from the MSB are not used for encoding in the horizontal and vertical blanking intervals. This is where information such as audio signals is multiplexed and transmitted, and the original video signal data has nothing to do with it.
Since no modification is required, signal processing is easy and system changes can be kept to a minimum.In addition, data signals such as audio signals can be processed using digital transmission lines whose transmission capacity is only one channel of video signals. It is possible to provide a time division multiplex transmission system that has features such as being able to multiplex and transmit the following information.

[Brief Description of the Drawings] Fig. 1 is a block diagram of a transmission system showing an embodiment of the present invention;
FIG. 2 is a block diagram of a receiving system showing an embodiment of the present invention.
FIG. 3 is a diagram for explaining the signal state of the horizontal blanking section of a composite video signal and the quantization state of the signal, FIG. 4 is a diagram for explaining an example of the configuration of the composite video signal, and FIG. 1 is a diagram for explaining an example of a frame structure on a conventional transmission path for video signals and audio signals. 1... Video encoding circuit, 2... Synchronization signal generation circuit,
3... Audio encoding circuit, 4... Video/audio multiplexing circuit, 5... Transmission line encoding circuit, 6... Transmission line frame generation circuit, 7... Optical transmission circuit (electrical-optical conversion circuit), 8... optical receiving circuit (optical-electrical conversion circuit), 9... transmission line decoding circuit, 10... transmission line frame synchronization circuit, 11... video/audio separation circuit, 12. ...Video and audio frame synchronization circuit, 13...Video decoding circuit, 14...Audio decoding circuit. tttt++t+tttttt Figure 3

Claims (3)

[Claims] (1) In a transmission method that multiplexes and transmits a composite video signal and a data signal other than the video signal, the composite video signal is linearly encoded, and the horizontal synchronization signal part excluding the vertical synchronization signal part, the horizontal retrace interval, or the vertical When a data signal other than the composite video signal is time-division multiplexed and transmitted by using predetermined upper bits that do not contribute to the encoding of the signal among the encoded bits of the signal in the retrace interval. Division multiplex transmission method. (2) The time division multiplex transmission system according to claim (1), wherein a frame signal necessary for separating the data signal is transmitted while being added to the data signal. (3) The time division multiplex transmission system according to claim (1), characterized in that the frame signals necessary for separating the data signals are transmitted by violating a coding rule of transmission codes.