JPS59117390A - System for transmitting color television signal - Google Patents

Abstract

PURPOSE:To improve the quality of PCM sound and the strength against an error added with redundancy by allocating a PCM sound signal to a part of a color burst to increase the number of PCM bits further. CONSTITUTION:After an input signal from a terminal 23 is clamped for the DC level at a clamp circuit 5 and a horizontal synchronizing signal at each other line is detected by a synchronism detecting circuit 7. The horizontal synchronizing signal on each alternate line is applied to a monostable multivibrator 8 to form a gate pulse inorder to extract only the horizontal synchronizing signal and the PCM signal. The PCM signal is obtained at a terminal 20 from an output of a cutout circuit 9 extracted by this gate pulse via a differential amplifier 19, the PCM signal enters a sound signal circuit, where the signal is demodulated. Further, the output signal of the cutout circuit 9 enters a tank circuit having a resonance frequency being one-half of the chrominance subcarrier frequency via an amplifier 10, and the horizontal synchronizing signal is obtained from a terminal 21 and the chrominance subcarrier is obtained from a terminal 22 by the circuit as shown in a figure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a color television signal transmission system in which an audio signal is digitized and multiplexed with a video signal No. 8 for transmission.

[Technical background of the invention and its problems]

The power of the TenVision signal transmission method is to convert the television signal into an analog video signal, digitize it into an audio signal, and multiplex and transmit both signals. A method is being considered.

In other words, (1) a carrier wave dedicated to audio is placed outside the band of the video signal, and the digital sound P signal is subjected to phase modulation (four-phase P
SK), (11) a method of superimposing a digital audio signal on a video blanking section of a video signal, (i
ii) A method of switching and superimposing an audio digitally modulated carrier with a modulated wave of a video signal in a video blanking interval is available.

This article particularly relates to the improvement of the conventional example of method (11), and FIG. 1 shows an example of the conventional signal form.

In the signal waveforms shown in FIG. 1, 1 is a horizontal synchronizing signal, 2 is a color carrier reference burst signal, 3 is a PCM audio signal, and 4 is a video signal. This is the multiplexed signal constructed during the -horizontal signal period.

Similarly, FIG. 2 shows another example of the conventional signal format, and signals of the same type as in FIG. 1 are given the same numbers.

In FIG. 2, in the first period, a horizontal synchronizing signal 1 is followed by a color burst 2, followed by a video signal 4, and a PCM
There is no audio signal 3. In the second cycle, there is no horizontal synchronizing signal 1, and the PCM audio signal 3 enters at the beginning of the horizontal flyback section, followed by the video signal 4.

In such a signal system, the horizontal flyback section normally occupies only about 16 inches of one horizontal period. In Fig. 1, horizontal synchronization signal 1, color burst 2, and PCM
Since the audio signal 3 is inserted, the time width occupied by the PCM audio signal 3 becomes extremely short. For this reason, the bit structure of the PCM becomes small and the information capacity tends to be insufficient.

For example, consider a system based on standard NT8C signaling.

For an audio human input signal band of 15 KHz, the sampling frequency must be at least twice that of the human input signal9, and it is assumed that sampling is performed at twice the frequency of the horizontal synchronizing signal (15.75 KHz). To maintain high quality for analog audio signals, approximately 914 bits per channel (S/
NL:, 86 dB), and 28 bits for 2 channels in stereo. Adding redundancy pictograms for word synchronization, error detection, correction, etc. to this results in 3
0 bit or more 1. When this PCM audio signal is inserted during the horizontal retrace interval (repetition frequency 15.75 KHz), 60 bits or more are required.

It depends on how you choose the PCM clock frequency.
If the maximum frequency must be within the video signal band 4.3 MI-h, it must be within 3 to 10 μs of the horizontal retrace interval.
It becomes impossible to insert all 60 bits of pulses during this period.

Also for the signal waveform in Figure 2, once every two horizontal synchronization signals
Despite the number of times, even PCM inserted over the entire horizontal retrace section has 6
0 bit is impossible.

[Purpose of the invention]

This invention is an attempt to improve the above-mentioned drawbacks of the conventional signal system, and to increase the number of PCM and signals to be inserted into the horizontal retrace section.

[Summary of the invention]

The present invention removes the color burst signal so that its portion K
This is a signal configuration in which a PCM audio signal is assigned and color burst carrier extraction is supplemented using a horizontal synchronization signal and a PCM bit extraction circuit.

〔Effect of the invention〕

With this invention, the total bit structure of PCM can be expanded to about twice that of the conventional one, so the quality of PCM audio can be improved against errors by adding redundancy, achieving high sound quality, and Interference between signals and audio signals is also caused by PC
[Embodiment of the Invention] An uninvented signal format is such that the PCM audio has a bit rate that is an integral multiple (1 to 2 times) of the color subcarrier frequency. The explanation will be given assuming that the color subcarrier is an integer multiple of the horizontal synchronizing signal frequency and an odd multiple of half the frequency.

FIG. 3 shows a system in which the color subcarrier frequency is an odd multiple of half the horizontal synchronization frequency in the signal form of the present invention.

The same signal VcH is given the same number as in FIG.

The diagram (a) consists of a horizontal synchronization signal 1, a PCM signal 3, and a video signal 4. Horizontal synchronization signal l is 2 cycles%
JJl has been inserted only once.

FIG. 5B is an enlarged view of the PCM signal 3 including one horizontal synchronization signal. In the same figure (b), the clock rate of PCM signal 3 is set to the color printing carrier wave frequency of the video signal (period is To
) VC is chosen equally. Since the pulse format of the PCM signal 3 is, for example, NRZ Hals, the interval between its rising and falling points depends on the frequency M(To) of the subcarrier. The pulse width (T1) of the horizontal synchronization signal 1 has a length M times (a positive integer) the clock rate (To),
The time T2 from the rising edge of the horizontal synchronization signal g1 until the start of the PCIVI signal 3 is the PCiV clock relay)
It is assumed that (To) is N times (positive integer) VC.

Then, when the horizontal synchronization signal 1 is inserted, the PCM signal is composed of an audio signal (including an error correction detection code) that does not include a certain pattern as a synchronization signal, and this horizontal section fn Make it a line. next n+i
Horizontal synchronization signal 1 is not inserted in line 1, and originally,
PCM signal 3 up to the part of horizontal synchronization signal 1 to be inserted
It is filled with. It is assumed that the PCM signal 3 on the (n+1)th line includes a synchronizing turn (1, 0, 1, 0 in a row) at the beginning of a word, followed by an audio signal.

As shown in the figure, it is assumed that the horizontal synchronizing signal 3 is inserted again into the (n+2)th line and is repeated.

FIG. 4 shows a configuration in which when such a signal is input, the horizontal synchronizing signal 1 is reproduced, the PCM signal portion is detected, and the color burst is extracted.

It is assumed that the signal shown in Figure i3 is input from the terminal 230 input terminal. Fluctuations in Ir1M flow level in clamp circuit 5? This will ensure the detection of the negative side synchronization signal. When the synchronization detection circuit 7 detects a horizontal synchronization signal every - line, it hits the monomulti 8 and detects the horizontal synchronization signal of the nth line (with Lus P and lag k in the PCM signal section) (Lus and the section of the PCM signal on the n+1th line:
A pulse with +g + is output.

This output pulse width U may be a rough value. The rectifier 6 serves to switch the horizontal synchronizing signal, which has hitherto been below the pedestal level (negative pulse), to a pulse (positive pulse) which is above the total pedestal level.

The extraction circuit 9 is driven by the output pulse of the monomulti 8 and extracts a horizontal synchronizing signal and a PCM signal. Then, level control is performed by the differential amplifier 19 to remove the horizontal synchronizing signal, and only the PCM signal is obtained from the terminal 20.

This output is t? “It enters the signal processing circuit and is demodulated.

The amplifier 10 increases the horizontal synchronization signal level to the same level as the PCM signal and enters the tank circuit 11 which has a resonant frequency tone that is half the color subcarrier frequency.

A waveform shaping circuit 12 converts the output of the tank 11 into an r pulse wave, and a differentiation circuit 13 obtains rising and falling signals of the pulse wave.

The positive current circuit 14 obtains a single current pulse wave. The pulse interval at this time is To. This pulse wave enters a phase locked loop (PLL) K. PLLH phase comparator 15 loop filter 16.2 times the color subcarrier frequency Crystal control 1dlVc . This is supplied to the color signal demodulation circuit as a reference signal.

VC) (017 to get the V horizontal sync signal [is now an odd number multiple of 2/2 of the horizontal sync signal, so for example, if you use a period of 55 minutes per month, 19, the output will be the horizontal sync signal from terminal 21. This output is naturally the original synchronizing signal that outputs output pulses in short periods.

In Figure 5, the color subcarrier frequency is an integer multiple of the horizontal synchronization signal v.
This is a signal waveform in the case of c, and the same signals as in FIG. 3 are represented by the same numbers and symbols. That is, the fifth
The configuration is the same as that of the n-line signal in FIG. 3(a) and FIG. 3(b). Therefore, the signal on the (n+1)th line also has the same configuration as that on the nth line.

The configuration shown in FIG. 6 makes it possible to extract color bursts and PCM signals when such signals are input manually. It has almost the same configuration as FIG. 4, and the same numbers are used to denote the same functions.

Reference numeral 25 in the figure shows a monomultiplier in which the width of one pulse for each horizontal synchronization pulse of the synchronization detector 7 is equal to one horizontal retrace interval.

Furthermore, the K PLL circuit is composed of a VCXO 26 that oscillates at the same frequency (period To) as the color subcarrier.

Therefore, when the PLL is synchronized, a demodulation reference signal is output from the terminal 22 as a color burst.

As described above, the present invention provides a signal that matches the rising and falling points of the pulse width of the horizontal synchronizing signal for clock extraction by using a part of the fixed pattern in the PCM signal or without using all the heat. Since the interval is constant, the clock bits can be reliably extracted even if the audio PCM signal is all zero or all '11'. Therefore, since the bit structure of the PCM signal can be expanded, it is possible to have a sufficient redundancy structure, and as a result, a high-quality audio signal can be transmitted and demodulated, and other characteristic sounds can be obtained.

[Brief explanation of drawings]

Stripe 1 shows the conventional signal form, Fig. 2 shows another conventional signal form, PJa shows the signal form of the present invention, and Fig. 4 shows the uninvented signal demodulation circuit configuration. Figure 5
The figure shows another signal form according to the invention, and FIG. 6 shows another signal demodulation circuit configuration according to the invention. Representative Patent Attorney Kensuke Norichika (and 1 other person)

Claims (1)

[Claims] The video signal is an analog signal, and the audio signal is PCM (a color television signal transmission method in which the signal is transmitted superimposed on a horizontal blanking section, and the pulse width of the horizontal synchronizing signal and the horizontal synchronizing signal). a color television set, characterized in that the interval between the pulse and the start pulse of the PCM signal is selected as an integer multiple of the period of the color subcarrier frequency, respectively;
signal transmission method.