JPS5923147B2 - Color television signal burst removal reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a burst removal reproducing apparatus that removes burst signals and synchronization signals from a composite color television signal, transmits the signal, and reproduces them on the receiving side.

When converting a color television signal into a digital signal and transmitting it, synchronization signals and burst signals other than video signals are predefined signals, so instead of faithfully transmitting these signal waveforms, these signals It is also possible to transmit a code representing the synchronization signal and reproduce the synchronization signal and burst signal on the receiving side.

The return period of television signals is about 20% of the total.
When carrying out so-called band compression transmission of television, a significantly compressed transmission can be achieved by removing the retrace period. Conventionally, blanking period elimination reproduction has been relatively easily achieved for black-and-white television or color television signals without subcarriers, but for color television signals with subcarriers. had the disadvantage that the phase of the burst signal could not be reproduced with high accuracy, resulting in color errors in the reproduced image. SUMMARY OF THE INVENTION An object of the present invention is to provide a stable burst removal reproducing apparatus with little phase reproduction error for color television signals with subcarriers.

That is, the present invention provides means for sampling and encoding a composite color television signal, means for generating a local subcarrier from a sampling pulse as a digital code string, means for multiply detecting a burst signal using the local subcarrier, and a synchronous sampling device comprising a means for automatically controlling the relative phase of the burst signal and the sampling pulse using the detection output so that the phase of the burst signal and the local subcarrier have a predetermined relationship; means for removing a period including a burst signal from a composite color television signal and generating a synchronization code indicating the position of the removed signal and a phase code indicating a reference phase of the burst signal and transmitting the same in place of the removed signal; 1. A burst removal reproducing apparatus for a color television signal, comprising means for detecting a phase code and reproducing a removed signal.

According to the present invention, since the synchronized sampling device generates a local subcarrier that is phase-synchronized with the burst signal, the reference phase of the local subcarrier can be used as the reference phase of the burst signal, so no adjustment is required. Furthermore, highly accurate phase reproduction can be achieved.

The present invention will be described below with reference to the drawings, taking an NTSC signal as an example, but the present invention can also be applied to other television signals such as PAL SECAM. FIG. 1 is a block diagram showing the configuration of the synchronous sampling device used in the present invention, and FIG.
The figure is a block diagram showing the burst removal and regeneration apparatus of the present invention.

First, the synchronous sampling device shown in FIG. 1 will be explained. N
TSC signal 1 is sampled and encoded by A/D converter 2. The A/D converter output is passed through a bandpass filter (BP
F) 3, components in the vicinity of the subcarrier frequency are extracted and subjected to product detection using the local subcarrier generated by the local subcarrier generator 5 in the detector 4. The sampling frequency Fs of the A/D converter is the subcarrier frequency Fsc. m. n(m
>n) is an integer.

Since the horizontal synchronization frequency FH of the NTSC signal is set to 2/455 of Fsc, the relationship (1) is satisfied, giving a wide degree of freedom in selecting the sampling frequency within a practically possible range. .

In the figure, 6 is a synchronization separation circuit, and 7 is a voltage controlled oscillator, which is used to generate a frequency-related sampling pulse as shown in equation (2) based on the horizontal synchronization signal that is synchronized and separated from the NTSC signal 1. It is a circuit. Further, 8 is a variable phase shifter for changing the phase of the sampling pulse. The local subcarrier generator 5 consists of an address generator 12 and a read only memory (ROM) 13. If the local subcarrier is continuous and S1(t)-Sin(2πFsct) (3), then t=k/Fs(k=O, 1, 2, . . .
The value sampled by ) is .

Therefore, if m sine function values from k=0 to k=m-1 are stored in ROM13, and the storage address of the ROM is periodically scanned and these values are read out, the local subcarrier is obtained. On the other hand, if the envelope of the color burst inserted into the back pouch is B(t), the burst signal is a continuous system, and S2(t)=B(t)Sin(2πFs
ct+θ) (5) Therefore, the multiplicative detection output by the local subcarrier is proportional to COSθ.

Therefore, in order to make the phase difference θ zero, it is sufficient to maximize the detection output. In this case, the phase difference is defined between the two inputs of the detector 4, but the delays in the BPF 3 and local subcarrier generation circuit 5 are known, so if these delays are taken into account in advance, the A/D The sampling phase at the converter output can be set to a desired value, and if this is branched and output, it can be used for various purposes. In order to realize such control, first, the detection output is extracted only during the burst period of the back porch by the gate 9, integrated by the integrator 10, and the result is led to the judgment circuit 11 to determine the magnitude and direction of the phase shift. , and feed back the determination result to the variable phase shifter 8 and the address generator 12 to freely control the deviation so that it becomes zero. In the figure, one of the sampling pulses
When a large phase shift greater than the period is detected, rough phase control is performed by controlling the address generator 12 and shifting the address by one address, and when a small phase shift is detected, the variable phase shifter 8 controls the address generator 12 to perform rough phase control. Performs minute phase control. The address generator may be controlled by, for example, temporarily stopping address scanning and generating the same address twice, or by momentarily skipping the address and skipping the first address. At the initial stage of phase pull-in, the rough phase is adjusted by this address control, and then the remaining minute phase shift is adjusted by controlling the variable phase shifter. In this way, the synchronous sampling device performs synchronous sampling on the NTSC signal 1.
a local subcarrier 104 phase-locked to the old and burst signal;
and generates an address 102 for local subcarrier generation. FIG. 2 is a block diagram showing the structure of the burst removal reproducing apparatus of the present invention, in which the NTSC signal 1 is synchronously sampled by the synchronous sampling apparatus 100 described above. The sampled and encoded NTSC signal 101 has a synchronization signal and a burst signal removed by a gate 20, and is further code-converted by a code converter 23. This code conversion is to convert the image signal into a code that is more efficient than the normal PCM code, for example, differential PC
M (DPCM) encoding, etc., and is optional in the present invention. A synchronization code generator 22 generates a gate signal and a synchronization code representing the removal start position based on the horizontal synchronization signal.

A phase code generator 21 generates a code representing the reference phase of the removed burst. These image codes, synchronization codes, and phase codes are multiplexed by a multiplexer 24 and sent out. Here, the synchronization code and the phase code will be explained in detail using FIG. 3.

(1) shows the synchronized portion of the television signal waveform, and (1) is sampled by the sampling pulse shown at 01[).

If the sampling pulses are numbered ``, 2, 3, etc.'' and the period from 1 to 100 is removed, the sampling position will be used as a synchronization code as is well known. It is sufficient to give a code indicating 1. ([[l] indicates the address 102 of the address generator for local subcarrier generation in the synchronous sampling device, and the address at sampling point 1 is B, and it indicates that the address increases by 1 address in order from here on. There is. Assuming that synchronous sampling is performed so that the phases of the local subcarrier and the burst match, if a code representing address B at sampling point 1 is sent as the phase code, the burst can be reproduced from this code. . Therefore, in FIG. 2, the phase code generator 21 can be realized by a register that holds the address 102 at the removal start time. In the reproduction system shown in FIG. 2, an image code is extracted from the received signal 36 at a gate '20 and converted to the original PCM code at a code inverse conversion circuit 27.

The synchronization detector 32 detects the synchronization code, and the synchronization signal generator 2
A synchronization signal corresponding to the synchronization signal removed by step 9 is generated. The phase code detector 31 detects the phase code and supplies it to the local subcarrier generator 5 to fix the reference phase of the local subcarrier. Since the local subcarrier generator has the same configuration as the one on the transmitting side, if only the reference phase is given, it generates a subcarrier that is in phase with the removed burst signal. A gate 26 cuts out the subcarrier and reproduces a predetermined burst signal.

The original NTSC signal is reproduced by multiplexing the image signal, synchronization signal, and burst signal using the multiplexer 25 and converting the signal into an analog signal using the D/A converter 33. Note that in the case of the PAL system, although the relationship in equation (2) is different, the basic principle is the same, so the present invention can be applied. Furthermore, in the SECAM system, since the back porch burst has a different frequency for each line, the present invention can be applied by focusing on only one of the bursts.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a synchronous sampling device used in the present invention, in which 2 is an A/D converter, 3 is a bandpass amplifier,
4 is a product detector, 5 is a local subcarrier generator, 6 is a synchronization separation circuit, 7 is a voltage controlled oscillator, 8 is a variable phase shifter, 9 is a gate, 10 is an integrator, 11 is a determination circuit, 12 is a The address generator, 13, is a read-only memory. FIG. 2 is a block diagram showing the burst removal reproducing device of the present invention, in which 100 is a synchronous sampling device, 20 and 26 are gates,
21 is a phase code generator, 22 is a synchronous code generator, 23 and 27 are code converters and inverse converters, respectively; 24, 2
5 is a multiplexer 29 is a synchronization signal generator, 31 and 32 are phase and synchronization code detectors, respectively, and 33 is a D/
It is an A converter. FIG. 3 is a time chart showing the operating principle of the present invention.

Claims (1)

[Claims] 1 A composite color television signal in which a luminance signal, a subcarrier-modulated color signal, and a subcarrier burst signal are multiplexed is transmitted at a frequency that is (m/n) times the subcarrier (m, n (m>n) is an integer). means for sampling and encoding with a sampling pulse; means for generating a local subcarrier having a frequency equal to the subcarrier as a digital code string based on the sampling pulse; and generating a back porch burst signal using the local subcarrier. A synchronous sampling device having means for performing multiplicative detection, means for monitoring the output of the multiplicative detection, and means for changing the relative phase of the burst signal and the sampling pulse by the output of the monitoring means; means for removing a period including a burst signal from a converted composite color television signal and generating a synchronization code indicating the position of the removed signal and a phase code indicating a reference phase of the burst signal and transmitting the same in place of the removed signal; 1. A burst removal reproducing apparatus for a color television signal, comprising means for detecting a code and a phase code and reproducing a removed signal.