JPH0142196B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for time-division multiplexing and encoding/decoding television (TV) signals.

As a method of encoding and transmitting a color TV (CTV) signal, there is a separate encoding method that separates and encodes a luminance signal and a color signal.

In this case, the color signal is time-compressed and time division multiplexed with the luminance signal.
TDM) and turn it into a single signal, it can be handled in the same way as a monochrome signal, and the monochrome encoding transmission system can be used as is to transmit color TV signals. In the conventional time division multiplexing method for color TV signals, two predetermined phase axes (I, Q axes, (R-Y), ( Since the phase information of the color burst signal is not required when modulating the baseband color signal to the carrier color signal on the receiving side, modulation is performed using the determined phase axis and the burst is It would be nice to add a signal. However, a phase lock is required to fix the phase axis.

On the other hand, if the phase axis is not determined, it is sufficient to add a burst signal and transmit it, but since the color burst signal conveys phase information, if it is digitized and transmitted, it is not necessary to transmit all the color burst signals, and two basic methods are used. The typical value of the color burst signal is 1 for each band color signal phase axis.
If each sample is used, the color burst signal can be reproduced on the receiving side, and the amount of transmitted information can be reduced. However, each must transmit only one sample.
If an encoding means having subsampling, filter processing, etc. is added to a system for transmitting a TDM color TV signal, the color burst signal cannot be reproduced correctly. Figure 4 shows that when the TDM color signal to which only one sample of the color burst signal representative value is added passes through a filter of H(z) = (1 + z ^-1 /2) ² , the color burst representative value is distorted. It shows how it is received. Note that FIG. 4 shows a case where the signal values other than the representative value of the color burst signal are constant values. The representative value of the color burst shown in FIG. 4a is distorted by this filtering as shown in FIG. 4b. As is clear from a comparison with Figure 4 a and b, if only one sample of the color burst representative value is sent, if encoding processing with filtering processing is added, the color burst will be correctly processed on the receiving side. It becomes difficult to play. Usually, a color television receiver performs automatic gain adjustment and automatic saturation adjustment so that the amplitude of the color burst signal becomes a reference value, so the distortion shown in Figure 4b is caused by the following: This is a huge problem.

Proceedings of the 1975 Conference of the Four Electrical Engineers of Japan 4-64
"Digital Processing Techniques for Color Signals" on pages 67 to 67 describes a method of multiplexing and transmitting the representative values of color bursts after the encoding process is completed, as a method for solving such problems. However, with this method, encoders and decoders developed for monochrome signals cannot be used as they are.

An object of the present invention is to provide an encoding device for a TDM color TV signal that can correctly reproduce a color burst signal even if subsampling, filter processing, etc. are applied to the TDM color TV signal when transmitting one portion of burst information. be.

The present invention will be described in detail below using examples.

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention. This embodiment shows a case in which an encoding method is added in which a TDM color TV signal is subsampled at a sampling frequency of 1/2 and then transmitted.

The decoded color television signal input to the input terminal 20 has a sampling frequency s of 4 times sc (sc
is the subcarrier frequency) A/D conversion circuit 1
After being converted into a PCM (Pulse Code Modulation) signal, the signal is separated into a luminance signal Y and a carrier color signal C in a luminance signal and color signal separation circuit 2. Demodulation circuit 3
demodulates the carrier color signal C to obtain baseband color signals C ₁ and C ₂ with a sampling frequency of 1/2 s (=2sc).
The baseband color signals C ₁ and C ₂ are sent to the color signal band limiting circuit 5 and each is band limited to approximately 1/6 sc, and then the sampling frequency becomes 1/12 s (= 1/3 sc). The signal is subsampled to 1/6 and sent to the TDM conversion circuit 6. The luminance signal Y is sent to the luminance signal band limiting circuit 4, where it is band limited to a band of approximately sc, and then subsampled to 1/2 so that the sampling frequency is 1/2 s (= 2 sc), and then sent to the TDM conversion circuit. Sent to 6. In the TDM conversion circuit 6, the luminance signal and the color signal are time-division multiplexed, and the sampling frequency is 1/2s, that is, 2sc.

TDM - Outputs CTV signals. If the multicode color television signal is an NTSC-color TV signal,
Since sc = 455/2 _H ( _H is the horizontal scanning frequency), 1 horizontal period section includes sample values of 455 samples.

In response to the input NTSC color television signal shown in FIG. 2a, the TDM conversion circuit 6 uses 364 samples of the video section as the luminance signal included in the signal as a color signal, as shown in Y in FIG. 2b. One sample at the approximate center of the color burst and 64 samples in the video section are selected as C ₁ or C ₂ as shown in Figure 2b, and the odd line as shown in Figure 2c is selected.
l ₀ , is time-division multiplexed into TDM-CTV signals for every even numbered line le and then output. The luminance signal is sent for each line, but the color signals are sent alternately line by line, and the receiving side reproduces the color signals that are not sent using the values of the previous line. In order to correctly transmit the phase information of the color burst signal even if subsampling and filter processing are added, the sample value of one sample of the color burst part is transmitted as a burst signal by overlapping the sample value for a period of 7 samples. I decided to do it. In this way, even if sub-sampling and filter processing are added, by extracting a value corresponding to the middle of the 7-sample section, a value that matches the sample value on the sending side can be obtained.

Here, the configuration of the TDM encoding circuit 6 will be explained. Although various configurations of the TDM conversion circuit are possible, an example configured using memory will be described with reference to FIG. 6. In FIG. 6, the address generation circuit 73 generates a write address signal, a read address signal, and a read/write address signal generated based on a vertical synchronization signal, a horizontal synchronization signal, and a clock signal.
The write signal is Y memory 70, _C1 memory 71,
These signals are supplied to the _C2 memory 72, but for simplicity, these signals are represented by one signal line in the drawing.

First, the Y signal written to the Y memory is the part excluding the horizontal blanking period (see Figure 2b).
is read out at the timing shown in FIG. 2c.

The read operation of the C ₁ memory 71 and the C ₂ memory 72 is performed every two horizontal scanning lines. The portion of the _C1 signal written in the _C1 memory 71 excluding the horizontal blanking period (see FIG. 2b) is read out only for odd-numbered scanning lines at the timing shown in FIG. 2c. On the other hand, in the C ₂ signal written in the C ₂ memory 72, the data of even scanning lines in the portion shown in FIG. 2b is read out at the timing shown in FIG. 2c. In this way, the Y signal and the line-sequential C ₁ /C ₂ signals are time-division multiplexed. In addition,
The representative value of the color burst signal can be obtained by arranging multiple identical sample values at the positions shown in Figure 2c by reading out the address where the peak value of the color burst signal is stored multiple times in succession. Can be done. In addition, in Fig. 1, the representative value of the color burst can also be obtained from the demodulation circuit 3, so the value obtained from the demodulation circuit 3 is transferred to the Y memory, _C1 memory, and _C2 memory within the TDM conversion circuit. may be stored in a separate memory and then multiplexed by multiple samples.

TDM output from TDM encoding circuit 6 -
The CTV signal is sent to a band compression encoder 17 consisting of a band limiting circuit 7 and a resampling circuit 8. The CTV signal sent to the band compression circuit 17 is sent to the band limit circuit 7
Bandwidth is limited. As a specific example of a filter that performs band limitation, there is a filter whose function represented by Z transformation is given by the following equation.

H ₁ (Z) = (Z ^-1 +2 + Z ¹ ) Z ^-1 /4 (1) TDM whose band has been limited by the band limit circuit 7 -
The CTV signal is resampled to 1/2 by the resampling circuit 8, and a TDM-CTV signal with a sampling frequency of 1/4 s (=sc) is output. Re-sampled TDM -
The CTV signal is sent from the output terminal 21 to the transmission line.

A TDM-CTV signal with a sampling frequency of 1/4s (=sc) input from the transmission line to the input terminal 22 is sent to the band compression decoder 18 composed of an interpolation circuit 9, interpolated by the interpolation circuit 9, and sampled. Outputs a TDM-CTV signal with a conversion frequency of 1/2s (= 2sc). In the interpolation circuit 9, the TDM-CTV signal with a sampling frequency of 1/4 s (= sc) has a sampling frequency of 1/2 s ( = 2sc) to obtain a TDM-CTV signal.

In this way, the band limiting circuit 7, the resampling circuit 8,
When the means of the interpolator 9 is added, the value of the burst signal becomes as follows. Figure 5a shows the case where seven samples of the representative value of the color burst signal are transmitted consecutively.
When the sample burst signal passes through the band-limiting filter given by equation (1), it becomes as shown in FIG. 5b. That is, only the middle 5 samples have the same value of A as the beginning, and when this burst signal is subsampled by 1/2, only 2 or 3 sample points have the same value as the beginning, depending on the subsampled phase. It will have the value of A. Therefore, when the interpolation circuit performs interpolation using the average value before and after, the middle 3 or 5 samples among the 7 samples of the burst signal will have the same amplitude value A as the beginning. Therefore, the color burst signal can be reproduced from the sample values of the burst signal transmitted with correct values.

Another specific example of the characteristics of the filter of the band limiting circuit 7 is a function represented by the following Z transformation.

H ₂ (Z)=(−3Z ⁻³ +19Z ⁻¹ +32+19Z ¹ −3Z ³ )Z ⁻³ /64 (2) The transmission of the burst signal when using the filter of formula (2) is as follows.

When a burst signal of seven samples having the same amplitude value A passes through the band-limiting filter given by equation (2), only one sample in the center has the same value of A as the beginning. Therefore, if the central sample holding the value of A is included in the signal sequence of the subsampled output when subsampled to 1/2 by the remarking circuit 8, the interpolation circuit Even if interpolation is performed using the average value, the central one sample among the seven samples of the burst signal will retain the initial amplitude value A. By appropriately selecting the number of samples to transmit the burst signal and the order of the function of the band-limiting filter, the values of the burst signal can be transmitted correctly even when a filter and subsampling means are added.

The TDM-CTV signal output from the interpolation circuit 9 is
The time-division multiplexed TDM-CTV signal is sent to the TDM inverse conversion circuit 10, where it is inversely converted, the luminance signal is sent to the luminance signal interpolation circuit 11, and the chrominance signal is converted from the currently sent signal C ₁ (or C ₂ ) and the previous line's color signal C ₂ (or C ₁ ) delayed by one horizontal scanning time are sent to the color signal interpolation circuit 12. Further, from the seven-sample burst signal that conveys the phase information of the color burst signal, one sample in the center holding the correct value is extracted and sent to the synchronization generation circuit 15 together with the one sample extracted in the previous line.

Here, one example of the configuration of the TDM inverse conversion circuit will be described with reference to FIG. 7. In addition, the seventh
In the figure, a write address signal, a read address signal, and a read/write signal are sent from the address signal generation circuit 83 to the Y memory 80 and the _C1 memory 8.
0, C ₂ is supplied to memory 81, but for simplicity,
It is represented by one signal line. In FIG. 7, the input TDM-CTV signal is distributed and written to the Y memory 80, _C1 memory 81, and _C2 memory 82 according to the write address signal and write signal supplied from the address signal generation circuit 83. The multiplexed Y signal, _C1 signal, and _C2 signal are separated. The Y signal is read out from the Y memory 80 and output. Also, the contents of _C1 memory and _C2 memory are read out twice in two horizontal scanning line periods.
A color signal C ₂ (or C ₁ ) delayed by one horizontal scanning time from the currently transmitted C ₁ (or C ₂ ) is output.

On the other hand, the TDM-CTV signal is also supplied to the latch circuit 84, and the central one of the color burst representative values successively sent from the transmitting side is
Only the sample is extracted by the latch pulse supplied from the address signal generation circuit 83.

The luminance signal interpolation circuit 11 performs interpolation,
A luminance signal with a sampling frequency of s (=4sc) is obtained and sent to the adder 14. C ₁ whose sampling frequency sent to the color signal interpolation circuit 12 is 1/12s (=1/3sc)
The color signals C 2 and C ₂ are each interpolated by a color signal interpolation circuit, and color signals C ₁ and C ₂ having a sampling frequency of 1/2s (=2sc) are outputted and sent to the color modulation circuit 13 . In the color modulation circuit, the baseband color signal C ₁ ,
A carrier color signal with a sampling frequency of s (=4sc) is obtained from C ₂ and sent to an adder 14 where it is added to the luminance signal and sent to a synchronization generation circuit 15 . Synchronization generation circuit 15
Then, a color burst signal is reproduced from the transmitted burst signal, a horizontal synchronization signal is added to create a synchronization signal, and a luminance signal and a carrier color signal are added to the added signal to reproduce NTSC color.
Decoding TV signals. Decoded NTSC color
The TV signal is converted into an analog signal by the D/A converter 16, and an analog NTSC color TV signal is obtained at the output terminal 23.

As a second embodiment of the present invention, a case will be described in which a TDM signal is encoded by an interframe encoding device having a subsampling method. The block diagram showing the configuration of the second embodiment is similar to the block diagram of the first embodiment shown in FIG. It consists of a decoder.

FIG. 3 shows a specific configuration example of the band compression encoder 17 and the band compression decoder 18 in the second embodiment. The band compressors 17 and 18 operate with subsampling when the mode signal is in the subsample mode, and without subsampling when the mode signal is in the standard mode.

The TDM-CTV signal input to the input terminal 31 is band-limited by the band-limiting circuit 32 and sent to the re-sampling circuit 33.
Sub-sampling is performed at 1/2 and sent to the switching transformer 35. Input terminal 3 sent to delay circuit 34
The TDM-CTV signal from 1 is delayed to be the same as the signal delay in the band limiting circuit 32 and sent to the switching converter 35. Switching transformer 3 depending on the mode signal
The signal selected in step 5 is subtracted from the predicted signal by a subtracter 36, and a predicted error signal is output and sent to a quantizer 37. The prediction error signal (quantized output) quantized by the quantizer is sent to a code conversion circuit 38 and an adder 39. In the adder 39, the quantized output and the predicted signal are added together and then sent to an interpolation circuit 41 and a delay circuit 42. In the delay circuit 42, the signal is delayed to be the same as the delay between the input and output of the interpolation circuit 41, and the signal is sent to the switching converter 43. Further, the signal interpolated by the interpolation circuit 41 is sent to the switching converter 43. The signal (locally decoded signal) selected by the switching converter 43 according to the mode signal is sent to the frame memory 44, and the delay in the delay circuit 42 (or interpolation circuit 41) and the delay in the frame memory 44 are combined into TV The frame memory 44 is configured to delay the signal by one frame time.
The predicted value is delayed by , and becomes the next predicted value, and one part is sent to the switching transformer 46 after subsampling, and the other is sent as is to the switching transformer 46 . In the switching converter 46, the predicted signal selected according to the mode signal is sent to the adder 39 and the subtracter 36. Code conversion circuit 3
The quantized output signal sent to 8 is subjected to blocking and variable length encoding, and a code-converted output signal is output as the output and sent to the transmission line.

In the band compression decoder 18 , the signal sent from the transmission path is processed in the code inversion circuit 51 and reversed to the code conversion circuit 38 .
A quantized output signal of the same level as input is outputted and sent to the adder 52.

In the adder 52, the predicted signal and the quantized output signal are added and sent to an interpolation circuit 54 and a delay circuit 55, which have the same functions as the interpolation circuit 41 and delay circuit 42, and the respective output signals are sent to a switching converter 56. .
A part of the signal (locally decoded signal) selected by the mode signal is sent to the output 61, and part of the signal is sent to the frame memory 57 which has the same function as the frame memory 44.
The predicted signal for the next sampling time is output as the output. A part of the predicted signal is sent to the sub-sampling circuit 4.
The output is sent to a sub-sampling circuit 58 having the same function as 5, and the output is sent to a switching transformer 60.
Then, some of the prediction signals are sent to the switching converter 60 as is. In the switching transformer 60, according to the mode signal,
The selected signal is sent to adder 52.

The switching converters 35, 43, 46, 56, and 60 are set to the a side when in sub-sampling mode by the mode signal.
In standard mode, each can be switched to side b.

The band-limiting circuit 32 is the band-limiting circuit 7, and the sub-sampling circuits 33, 45, and 58 are the re-sampling circuit 8.
The interpolation circuits 41 and 54 have the same function as the interpolation circuit 9.

If the color signal of the TDM signal is line-sequential, the number of horizontal lines is 525, an odd number, with a difference of one frame, so C ₁ and C ₂
The phase of the color signals does not match. Therefore, the color signals _C1 and _C2 are reset every frame.
It is possible to match the phases of the two.

As explained above, TDM encoding involves separating a color TV signal into a luminance signal and two baseband chrominance signals, time-compressing and multiplexing the chrominance signal during the horizontal blanking period of the luminance signal, and converting and inversely converting the signal to a TDM signal. When the decoding device separates the subcarrier SC into two color signals without fixing the phase and transmits the color burst signal including the amplitude and phase information, multiple samples of the representative value of the color signal in the color burst interval are continuously sampled. The signal is included in the color signal of the video section as an amplitude phase information signal and converted to a TDM signal, and the receiving side uses the center value of the signal indicating phase information as the amplitude phase information signal to reproduce the color burst signal. By doing so, even if filter processing or subsampling is applied to the TDM signal, the phase information of the color burst signal can be transmitted correctly.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the first embodiment of the present invention, Fig. 2 is an explanatory diagram showing the relationship between color TV signals and TDM signals, and Fig. 3 is a band diagram of the second embodiment of the invention. A block diagram showing a specific configuration of a compression encoder/decoder, FIGS. 4a and 4b are diagrams for explaining the problems to be solved by the present invention, and FIGS. 5a and 5b are diagrams for explaining the effects of the present invention. Figure for, No. 6
7 are diagrams showing configuration examples of a TDM conversion circuit and a TDM inverse conversion circuit, respectively. In the figure, 1 is an A/D conversion circuit, 2 is a luminance signal/chrominance signal separation circuit, 3 is a demodulation circuit, 4 is a luminance signal band limiting circuit, 5 is a chrominance signal band limiting circuit, and 6 is a chrominance signal band limiting circuit.
TDM conversion circuit, 7 is band limiting circuit, 8 is resampling circuit, 9 is interpolation circuit, 10 is TDM inverse conversion, 1
1 is a luminance signal interpolation circuit, 12 is a color signal interpolation circuit,
13 is a color modulation circuit, 14 is an adder, 15 is a synchronization generation circuit, 16 is a D/A converter, 17 is a band compression encoder, and 18 is a band compression decoder.

Claims (1)

[Claims] 1 means for separating a color television signal into a luminance signal and a carrier color signal; means for separating the carrier color signal into two baseband color signals; means for time-division multiplexing during the horizontal blanking period, and a representative value of the amplitude of the color burst of the color television signal;
a TDM conversion device comprising means for further time-division multiplexing on the output of the multiplexing means to generate a TDM color television signal; means for reproducing two color signals and time-expanding the two color signals and outputting the two color signals; an extraction means for extracting, a means for reproducing a carrier color signal from the two time-expanded color signals, and a color burst generated based on the output of the extraction means while adding the reproduced luminance signal and the carrier signal. means for reproducing the color television signal by adding
A TDM color television signal conversion and inverse conversion device consisting of a TDM inverse conversion device;