JPS6059790B2 - Color television signal processing system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal processing method for ensuring the synchronization information of a color television signal obtained by time-division multiplexing of a luminance signal and a color signal to enable recording. It is.

All of the color television systems currently in use as standard broadcasting systems in various countries transmit television signals in which color signals are superimposed on the high-frequency portion of luminance signals using subcarriers. .

This method is extremely well constructed for broadcasting purposes, but because the color composite signal has a strong component (carrier color signal) in the high frequency region, it is difficult to apply it to baseband transmission over a cable. Since the higher the frequency, the larger the signal becomes, inter-channel crosstalk becomes a problem. Furthermore, since strict transmission characteristics are imposed on high frequencies, it is inappropriate to apply a system similar to the broadcasting system to baseband transmission. As a method suitable for baseband transmission, there is a method that focuses on the narrow required band of the color signal, compresses the time axis, and multiplexes the color signal and the luminance signal in a time-division manner.

The signal spectrum of this system is almost the same as that of the black-and-white television system, and is suitable for baseband transmission, although the required band of the chrominance signal is narrower than that of the luminance signal.
At least 0.5MH2 is required, and in order to compress the time and fit it into the same band as the luminance signal, the limit is to compress it to about 118, so if you want to time-division multiplex this with the luminance signal, The effective scanning period of the signal must be sacrificed to some extent. In particular, the synchronization signal width must be narrowed to the minimum necessary. This requirement is even stronger when audio signals also need to be multiplexed in a time division manner. In addition, this system is convenient for recording onto magnetic tape, etc., as the signal spectrum is similar to that of the black-and-white television system.
It may also be possible to record the video using a video tape recorder. However, VTRs are prone to image quality deterioration due to jitter, dropouts, etc., so in order to minimize the effects of this and to reduce malfunctions due to noise, the input signal should be one with a somewhat wide synchronization signal width. desirable.

In actual VTRs, the horizontal sync signal width and back porch of the current standard signal can be close to 5 microseconds, and most VTRs will not function properly unless both the synchronizing signal width and back porch of the input signal are approximately 3 microseconds or more. It is. Therefore, although the signal spectrum of the method of time-division multiplexing of the luminance signal and the time-compressed chrominance signal is easily compatible with ■TR, synchronization becomes a problem.
It has the disadvantage that it cannot be combined with a general ■TR. The present invention has been made to solve the drawbacks of the prior art, and an object of the present invention is to make a television signal obtained by time-division multiplexing a luminance signal and a time-compressed chrominance signal into a general-purpose television signal. (2) To provide a signal processing method that enables recording by coupling to a TR.

The gist of the structure of this invention is to focus on the fact that in general television receivers, in order to maintain scanning linearity and other reasons, there is so-called "skipping", that is, a considerable portion that does not actually appear on the screen during the effective scanning period. ,■When recording to TR, use part of the sync signal period as the sync signal period to expand the sync signal width, and when playing back after recording, the sync signal, brightness signal, color In order to restore the time relationship with the signal, the configuration is such that the reverse conversion of compressing the synchronization signal width can be performed.

Hereinafter, this invention will be specifically explained using the drawings. 1st
The figure is a signal waveform diagram showing an example of a television signal format of a color television system to which the present invention is applied.

In the signal waveform diagram shown here, in addition to the luminance signal and the time-compressed color signal, the audio signal is also time-division multiplexed, but the presence or absence of the audio signal is important for this invention. (↓No. Two types of color signals are transmitted alternately for each line. Also, the pulse width of the horizontal synchronizing signal is 2 μsec. Figure 2 shows an embodiment of this invention. This is a block diagram showing the main parts of the system of the signal processing method used during recording.
is a signal input terminal, 2 is a clamper, 3 is a synchronous signal separation circuit (comparator), 4 is an inverter, 5 is a horizontal synchronous signal separation circuit, 6 and 7 are monostable multivibrators, 8 is an inverter, and 9 is a synchronous signal Level adjustment circuit, 1
0 is an inverter, 11 is a delay circuit, 12 is a gate circuit,
13 is an adder circuit, and 14 is a signal output terminal. FIG. 3 is a signal waveform diagram showing an example of the format of the output signal obtained from the output terminal 14 of FIG.

FIG. 4 is a block diagram showing another main part of an embodiment of the present invention, and shows a system diagram of a signal processing method performed during playback after recording.

In the figure, 15 is a signal input terminal, 16 is a clamper,
17 is a synchronizing signal separation circuit (comparator), 18 is an inverter, 19 is a delay circuit, and 20 is an N. AND circuit, 2
1 is a delay circuit, 22 is a synchronizing signal level adjustment circuit, 23 is a slicer, 4 is an adder circuit, and 25 is a signal output terminal.
Next, the operation will be explained with reference to FIGS. 1 to 4.

A television signal having the format shown in FIG. 1 is input from the signal input terminal 1 in FIG. Clamp it so that it is

Then, the synchronization signal separation circuit 3 separates the synchronization signal,
The inverter 4 inverts the polarity to make it positive. Next, the horizontal synchronization signal separation circuit 5 extracts only the horizontal synchronization signal. The horizontal synchronization signal thus extracted is guided to monostable multivibration routers 6 and 7, each with a pulse width of 3.
μ seconds and 6 μ seconds. The polarity of the horizontal synchronizing signal having a pulse width of 3 μsec is inverted by the inverter 8, and the horizontal synchronizing signal has a negative polarity. This is a horizontal synchronizing signal with an expanded pulse width to be input to the TR, and the level is adjusted by the level adjustment circuit 9 and added to the video signal. On the other hand, the horizontal synchronization signal with a pulse width of 6 μs is
The audio multiplexing section and the horizontal synchronizing signal section of the composite image signal (television signal) whose polarity is inverted by the inverter 10 and delayed by 3 microseconds by the delay line 11 are transferred to the gate circuit 12.
It is used as a gate signal for removal. The gate circuit 12 has the output power level 6 of the inverter 10.
It is turned off only for microseconds and operates to set the signal level of the audio multiplexing section and the horizontal synchronization period to 0V. The thus obtained image signal without a horizontal synchronizing signal and the horizontal synchronizing signal whose pulse width has been expanded from the output of the synchronizing signal level adjustment circuit 9 are added by an adder circuit 13 to produce a signal in the form shown in FIG. The signal is taken out from the signal output terminal 14 and recorded on a VTR (not shown). Next, the case of playback will be explained.

In order to reproduce an image using a device with the same configuration, whether it is a reproduction signal from a VTR (not shown) or a television signal as shown in FIG. The time relationship of
It is necessary to make the signal the same as that of the signal shown in the figure, and it is necessary to perform conversion processing that is inverse to the signal processing in the case of Fig. 2. In Fig. 4, the signal coming from the signal input terminal 15 is ■
There is a reproduction signal from the TR, which has the format shown in FIG.

It is clamped by the clamper 16 so that the back pouch becomes 0V. The output of the clamper 16 is branched into two branches, a synchronizing signal is separated from one of them by a synchronizing signal separation circuit 17, and the polarity is inverted by an inverter 18 to form a composite synchronizing signal of positive polarity. It is branched into two branches, one of which is delayed by 1 μsec by a delay circuit 19, and NANDed with a signal that is not delayed by a NAND circuit 20. NAND circuit 20
The output becomes a composite synchronization signal of negative polarity in which the pulse width of the horizontal synchronization signal is 2 μsec. This is further delayed by 2 p seconds by the delay line 21, so that the time relationships among the synchronization signal, color signal, and luminance signal are the same as those of the signals shown in FIG. Then, the level adjustment circuit 22 sets the synchronization signal level to 0.3 with respect to the composite image signal amplitude 1, and the slicer 23 adds the synchronization signal portion of the input signal to the image signal by the addition circuit 24. The signals are added together and taken out from the signal output terminal 25. The time relationship between the synchronizing signal, the color signal, and the luminance signal taken out from the output terminal 25 is the same as the signal shown in FIG. Although the above explanation does not specifically mention audio signal processing, when recording,
If the audio signal is separated and connected to the audio input terminal of the TR, and the audio signal is multiplexed with the image signal by pulse amplitude modulation during reproduction, the audio signal can also be handled by the TR. As explained above, according to the present invention, color can be obtained by time-division multiplexing a luminance signal and a time-compressed color signal using a simple circuit that combines a delay line, a gate circuit, a comparator (synchronizing signal separation), etc. Television signals can be recorded and played back on a general VTR.

The signal spectrum of the above-mentioned color television system is almost the same as that of the black and white system, so the TR can be used for black and white, and any VTR can economically record and play back color images. There are advantages.

[Brief explanation of drawings]

FIG. 1 is a signal waveform diagram showing an example of a television signal format 9 of a color television system to which the present invention is applied, and FIG. 2 is a block diagram showing the main parts of an embodiment of the present invention. System diagram of signal processing method, Part 3
2 is a signal waveform diagram showing an example of the format of the output signal obtained from the output terminal 14 of FIG. 2. FIG. 4 is a block diagram showing other main parts of an embodiment of the present invention. FIG. 3 is a system diagram of a signal processing method performed during subsequent reproduction. Symbol explanation, 1...Signal input terminal, 2...
・Clamper, 3... Synchronous signal separation circuit, 4...
... Inverter, 5 ... Horizontal synchronization signal separation circuit, 6, 7 ... Monostable multivibrator, 8
...Inverter, 9...Synchronization signal level adjustment circuit, 10...Inverter, 11...Delay circuit, 12...Gate circuit, 13...・・・
・Addition circuit, 14...Signal output terminal, 15...
...Signal input terminal, 16...Clamper, 1
7... Synchronous signal separation circuit, 18... Inverter, 19... Delay circuit, 20... NA
ND circuit, 21...Delay circuit, 22...Synchronizing signal level adjustment circuit, 23...Slicer, 24...
...Addition circuit, 25...Signal output terminal.

Claims (1)

[Claims] 1. A color television signal processing method in which a luminance signal and a chrominance signal are time-division multiplexed in units of horizontal scanning periods, and means for expanding the pulse width of a horizontal synchronizing signal when recording the television signal; 1. A color television signal processing system comprising means for compressing and restoring the pulse width when playing back after recording.