JP2772520B2 - Color television signal encoding / decoding device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an encoding / decoding device for encoding and transmitting a color television signal with high quality. [Prior Art] When a composite color television signal is coded and transmitted, since the prediction method and the interpolation method are often limited if the composite color television signal having the subcarrier _fsc is directly encoded, the composite color television signal is converted into a luminance signal. And two separate baseband color signals before encoding. Among them, as an efficient method, a TD that multiplexes a chrominance signal into a horizontal synchronization portion of a luminance signal so that it can be treated as one signal.
There is a method called an M signal method or a TCI method. A conventional example of the TDM system using digital signal processing is CS79-69 (July 1979).
Are known. Luminance signal sampled at the sampling frequency f _s in this manner is encoded into 2 minutes subsampled by TDM signal 1 after receiving a band limited to the frequency band of 1 / 4f _s. Therefore, the bandwidth of the luminance signal which can be reproduced on the reception side in the following 1 / 4f _s, for example, roll-off when the filter of f _s = 4f _sc is taken into consideration, the bandwidth is conspicuous blur insufficient resolution becomes 3MHz or less equal There are disadvantages. [Object of the Invention] An object of the present invention is to provide an encoding / decoding apparatus capable of eliminating the above-mentioned disadvantages and reproducing a color television signal in which the resolution of a luminance signal does not deteriorate even when performing TDM encoding. [Constitution of the Invention] The color television signal transmission apparatus of the present invention uses a line correlation for a composite color television signal sampled at a sampling frequency that is at least twice the bandwidth of the input color television signal and an integer multiple of the horizontal synchronization frequency. Means for separating the carrier chrominance signal into a luminance signal in which the carrier chrominance signal is suppressed by a comb filter, means for demodulating the carrier chrominance signal into two baseband color signals, and means for band-limiting the two color signals Means for subsampling the two band-limited chrominance signals to an integral number and outputting the result; and aliasing distortion caused by subsampling with respect to a high-frequency signal of the luminance signal is caused by a carrier chrominance signal by a comb filter. The luminance signal is converted line by line so that
A color television signal comprising: means for sub-sampling by 180 degrees with a phase shift of one-half, and means for multiplexing and outputting the sub-sampled color signal to a part of a synchronizing signal of the sub-sampled luminance signal An encoding device; means for receiving and separating a multiplexed signal from the encoding device and outputting a luminance signal and two color signals in accordance with the phases subjected to sub-sampling by the encoding device; Means for interpolating a signal with a two-dimensional interpolation filter using line correlation to remove aliasing distortion of a luminance signal aliased to a frequency portion of a suppressed carrier chrominance signal; Means for interpolating the two color signals, means for modulating the two interpolated color signals with subcarriers to obtain a carrier color signal, A color television signal decoding device comprising means for adding a color transmission signal and reproducing a composite color television signal, and without using a band-limiting filter for sub-Nyquist sampling on the transmission side. A color television signal encoding / decoding device capable of reproducing a luminance signal having a frequency higher than half the sub-sampling frequency with high quality. It is composed of According to the present invention, by performing line offset sub-sampling on the luminance signal in consideration of the use of a comb filter using line correlation for YC separation, even if the TDM signal of the same frequency band is transmitted A luminance signal having a wider frequency band can be reproduced as compared with the related art, and a high-quality television image with high resolution and low blur can be obtained. Embodiment Next, the present invention will be described in detail with reference to the drawings. FIG. 8 is a block diagram showing a conventional encoding / decoding device. In Figure 8, the sampled NTSC color television signal at a sampling frequency f _s of the f _s = 4f _sc is separated into a carrier chrominance signal C and luminance signal Y in YC separation circuit 3. The luminance signal is band-limited to a frequency band of 1/4 _fs as shown in FIG. 10 (a) by the band-limiting filter 85, and then divided by the re-sampling circuit 87 as shown by X in FIG. Subsampled to 1. The carrier chrominance signal is demodulated by a demodulation circuit 4 into two baseband chrominance signals having a sampling frequency of 1/2 _fs , and then band-limited by a band-limiting filter 5 to a band of 1/24 _fs . Two color signals can show as a color signal having a period of 1 / f _s are multiplexed alternately every sampling. The band-limited chrominance signal is sub-sampled by the re-sampling circuit 7 at a sampling frequency of 1/12 as indicated by a circle in FIG. In the TDM encoder 9, as shown in FIG. 4, a chrominance signal is multiplexed in a line-sequential manner at a horizontal synchronization portion of the luminance signal and transmitted. On the receiving side, the TDM complex 12, the resampling circuits 88 and 15, the interpolation filters 86 and 1
7, the modulation circuit 18, the transmission side and the reverse process is performed sampling frequency by using an adder 19 to reproduce the digital signal of f _s D / A
The converter 20 converts the signal into an analog signal and outputs the analog signal. The frequency band of the luminance signal of the reproduced signal is 1/4 _fs or less, which causes the above-described problem of insufficient resolution. FIG. 1 is a block diagram showing one embodiment of the present invention.
The NTSC color television signal sampled at the sampling frequency f _s , for example, f _s = 4f _sc by the A / D converter 2 of the color television signal encoding device, is conveyed with the luminance signal by the YC separation circuit 3 using a line memory. Separated into color signals. The luminance signal is shown in FIG.
Has the same frequency band as the band limited by the filter having the characteristic shown in FIG. In response to the control signal from the control circuit 8 in the resampling circuit 6, the luminance signal is output for each of the odd-numbered lines and the even-numbered lines as indicated by X in FIG.
It is subsampled at 1/2 _fs with a phase difference of degrees. When sub-sampling is performed at 1/2 _fs , a folded spectrum as shown by a hatched line in FIG. 10 (c) occurs.
The carrier chrominance signal is demodulated by the demodulation circuit 4 into two baseband chrominance signals, controlled to a frequency band of 1/24 _fs by the band-limiting filter 5, and is indicated by a circle in FIG. as it is subsampled by 1/12 of f _s. In the TDM encoder 9, the chrominance signal is multiplexed in a line-sequential manner in the synchronization section of the luminance signal. That is, in one line of the television signal as shown in FIG. 4 (FIG. 4 (a)), Figure 4 (b), the luminance signal Y _i and the color signal C _1i / C _2i image segment shown in (c) and the color signal B ₁ / B ₂ burst portion T format of FIG. 4 (d)
Multiplexed to DM signal. Color signals are odd lines B ₁ and C
_1i is, B ₂ and C _2i is selected in the even lines. The TDM decoder 12 of the color television signal decoder decodes the received TDM signal to reproduce a luminance signal (FIG. 4 (e)) and two color signals (FIGS. 4 (f) and (g)). .
The signal levels P ₁ and P ₂ of the synchronization portion of the luminance signal are transmitted as a representative value using a vertical synchronization section or the like. Information on the sampling phase of the luminance signal is also sent. In the resampling circuit 14, the control circuit
The sample points have not been sent in accordance with the phase of the subsampling on the transmission side in response to the signal from 13 to interpolate the signal level of 0 is output as the luminance signal of the sampling of f _s. The interpolation filter 16 has a frequency characteristic as shown in FIG.
A luminance signal from which aliasing distortion has been removed by a dimensional filter is obtained. That is, the luminance signal separated by the Y / C separation circuit 3 using the line correlation is band-limited by frequency characteristics as shown in FIG. 10 (b). That is, 1 /
Only become spectrum to focus on an even multiple of the frequency of the 2f _H. 1 / 2f by shifting the phase for each line by the resampling circuit 14.
_When sub-sampling is performed on _s , the spectrum of the luminance signal from 0 to f _c2 shown in FIG. 10 (b) returns to the center of the frequency of 1/4 f _s , and the spectrum returns as shown by the oblique line in FIG. 10 (c). Occurs. At this time, the turns overlap. Even multiple of the luminance signal spectrum of 1 / 2f _H in between the frequency of approximately f _c1 ~f _c2 is 1 / 2f _H
A folded spectrum is generated at an odd number of times. This signal is sent to the receiving side. In the receiving side receives the luminance signal having the above-described folded spectrum, through a two-dimensional comb interpolation filter 16 using the line correlation After sampling frequency is the luminance signal f _s by performing 0 interpolation , To remove folding distortion. That interpolation filter has a filter characteristic such as FIG. 10 (b), the luminance signal sampling frequency is f _s with folded spectrum as shown in FIG. 10 (c), the interpolation filter 16
Aliasing is removed by passing through, 1 / 2f and the low frequency components of the frequency up to 0 to F _c1, at frequencies up to f _c1 ~f _{c2
As a result,} a luminance signal composed of high frequency components concentrated on even multiples of _H is obtained. Against resampling circuit 15, two color signals, not sent to the sample point interpolating the signal level of ○ obtaining two color signals sampled in 1 / 2f _s, and aliasing in the interpolation filter 17 removed, to obtain a carrier chrominance signal by modulation circuit 4 modulates subcarriers of f _sc. The luminance signal and the carrier chrominance signal are added to reproduce a digital color TV signal, and the D / A converter 20
Is converted to an analog signal. Band of the luminance signal of the reproduced TV signal can reproduce frequencies higher than 1 / 4f _s up to f _c2 in Figure No. 10 (b). As is clear from the description of the embodiment of FIG. 1 described above, the present invention separates a color television signal into a baseband luminance signal and a chrominance signal and performs time-division multiplexing on the luminance signal. With sampling applied,
By limiting the sub-sampling method and the Y / C separation method using line correlation, the same effect can be realized by the Y / C separation circuit 3, and the hardware can be simplified and a high-resolution image can be transmitted. Next, color signal interpolation will be described in more detail. Third
In the figure, the sample points (indicated by the circles) of the transmitted color signal have a frequency of 1/12 _fs . In order to make this color signal a signal with a frequency of 1/2 _fs , the sample points indicated by ○ sent for the remaining five sample points that are not sent Is interpolated as is. That is, 0-order hold interpolation is performed. Thus in the Figure 3 ○ values of points ○ mark every become total of five sampling points at sample point f _s after the sign of the sample points are interpolated. If a difference in delay occurs between the luminance signal and the chrominance signal after performing the zero-order interpolation, delay correction is performed. 1 / signal components of the color signal of the sampling of the 2f _s is 1 / 12f luminance signal reproduced from the interpolation filter 16 but half up to having the characteristics of comb _s has a high signal component than 1 / 4f _s Therefore, the signal component of the television signal to be synthesized and reproduced has a frequency higher than 1/4 _fs . Next, the resampling circuits 14 and 15 will be described in detail.
The luminance signal sampling period of 1 / 2f _s sent in resampling circuit 14, a signal sampling period of f _s by performing interpolation. In the embodiment of the present invention, the interpolation is a zero interpolation type in which a signal level of zero is interpolated. For example frequency luminance signal string of the period of _{1 / 2f s Y 1, Y} 2, Y 3 ... in the case where the sent, the luminance signal string of the period of the frequency of 0 in the after interpolation is f _s is Y _1, 0 , Y ₂ , 0, Y ₃ ,
0, ... In the resampling circuit 15, zero-order hold interpolation is performed. For example, a color signal train having a frequency of 1/12 _fs is C ₁ , C ₂ ,
When C ₃ ,... Are sent, the color signal sequence resampled by the zero-order hold interpolation at a sampling period of 1/2 _fs is C
_{1, C 1, C 1,} C 1, C 1, C 1, C 2, C 2, C 2, C 2, C 2, C 2, C 3, C 3, C 3, C 3, C 3,
C ₃ ... FIG. 2 is a diagram showing a specific circuit of the YC separation circuit 3.
The separation circuit 3 includes line memories 22 and 23 for delaying one horizontal period H and multipliers 24 and 2 having coefficients of −1,, and / 4.
5, 26, an adder 27, a band-pass filter 28 for passing the carrier chrominance signal, and a subtractor 29. Output terminal 3
At 0 and 31, a luminance signal and a carrier chrominance signal are obtained. Here, a circuit for delay / phase matching for the band-pass filter 28 is omitted. A digital filter having a frequency characteristic of a transfer function represented by the following equation is used as a filter characteristic of the band-pass filter 28 that blocks a low band and passes a carrier chrominance signal. The frequency characteristic of the transfer function from the input terminal 32 to the output terminal 30 in FIG. 2 is not the characteristic as shown in FIG. 10B, but the luminance signal of the TV signal is band-limited, Four.
FIG. 10 (b) shows a signal band of 2 MHz and a luminance signal. (1) When f _c1 of formula is about 1.8 MHz (-3 dB), f _c2 is approximately 4.2MHz for NTSC signals. FIG. 5 is a diagram showing a specific configuration of the TDM encoder 9 and the TDM decoder 12. The TDM encoder 9 stores the luminance signal and the two chrominance signals in the line memories 43 and 44 and performs switching by the switching circuit 46 in accordance with the signal from the control circuit 45, and the TDM signal of the format shown in FIG. Is output. Level detection circuit 42
In, the representative value of the signal level of the synchronous part is detected and output,
It is multiplexed for each field and sent. In the TDM decoder 12, the chrominance signal is stored in the line memory 50, and the signal level of the vertical synchronizing part is stored in the level generator 49, and in accordance with the signal from the control circuit 51, FIGS.
The luminance signal and the two color signals shown in (g) are reproduced. However, the color signals are alternately multiplexed for each sample to simplify the circuit. FIG. 6 is a diagram showing a specific configuration of the interpolation filter 16. The interpolation filter 16 has line memories 61 and 62 and a coefficient 1
/ 4, 1/2, 1/4 multipliers 63, 64, 65, adders 66, 69, a low-pass filter 67 and a band-pass filter 68. The frequency characteristics of the low-pass filter 67 and the band-pass filter 68 are set, for example, to be the same as the characteristics of the following equation. The frequency transfer characteristic is as shown in Fig. 10 (b). In this case,
f _c1 = 1.8 MHz and f _c2 = 5.4 MHz. FIG. 7 is a diagram showing another specific configuration of the YC separation circuit 3. As shown in FIG. When the band of the input color television signal is not restricted, it is better to restrict the luminance signal as shown in FIG. 10 (b) because the influence of aliasing distortion is small when reproduced on the receiving side. High quality images can be obtained. Line memory 7
2, 73, multipliers 74, 75, and 76, and a band-pass filter 78 have the same functions as those in FIG. A luminance signal and a carrier chrominance signal are obtained from the output terminals 81 and 82, respectively. For example, the frequency characteristic of the high-band rejection filter 80 that limits the band of the luminance signal is represented by the following equation. In this case, f _c1 = 1.8 MHz and f _c2 = 5.4 MHz. The sampling frequency f _s does not need to be f _s = 4f _sc but may be at least twice the Nyquist frequency and an integer multiple of the horizontal period frequency f _H so as to enable one-line delay. However demodulator and modulator is not as simple as in the case of f _s = 4f _sc, digital demodulator and modulator are required using a multiplier or the like. [Effects of the Invention] As described above, according to the present invention, it is possible to reproduce a broadband luminance signal as compared with the conventional TDM signal system, and to obtain a high-resolution television signal with less blur.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of the present invention, FIG. 2 is a diagram showing a specific example of a YC separation circuit, and FIG. 3 is a diagram showing a subsampling relationship of the present invention. FIG. 4 is a view for explaining a TDM signal, FIG. 5 is a view showing a specific example of a TDM encoder 9 and a TDM decoder 12, and FIG. 6 is a view showing a specific example of a band limiting filter 16. FIG. 7 is a diagram showing another specific example of the YC separation circuit 3, FIG. 8 is a block diagram showing a conventional configuration example, FIG. 9 is a diagram showing a subsampling relationship of the conventional example, and FIG. 9 is a diagram for explaining a band of a luminance signal. In the figure, 2 ... A / D converter, 3 ... YC separation circuit, 4
…… Demodulation circuit, 5,85 …… Band limiting filter, 6,7,14,15,
87,88 ... Resampling circuit, 8,13,45,51 ... Control circuit, 9
... TDM encoder, 12 ... TDM decoder, 16, 17, 86 ... interpolation filter, 18 ... modulation circuit, 19, 27, 66, 69, 77 ... adder,
20 ... D / A converter, 22,23,43,44,50,61,62,72,73 ... Line memory, 24,25,26,63,64,65,74,75,76 ... Multiplier,
28,68,78 …… Bandpass filter, 29,79 …… Subtractor, 42,
49: Level detector, 46: Switching circuit, 67: Low-pass filter, 80: High-band rejection filter.

Claims (1)

(57) [Claims] A composite color television signal sampled at a sampling frequency that is at least twice the bandwidth of the input color television signal and at an integer multiple of the horizontal synchronization frequency, using a line correlation and a carrier color signal and a luminance obtained by suppressing the carrier color signal using a comb filter. Means for separating the carrier color signal into two baseband color signals; means for band-limiting the two color signals; and dividing the two band-limited color signals by an integer. Means for sub-sampling to 1 and outputting, so that aliasing distortion caused by sub-sampling with respect to the high-frequency signal of the luminance signal is aliased to a frequency portion where the carrier color signal is suppressed by the comb filter. Means for sub-sampling the luminance signal by half by shifting the phase by 180 degrees for each line, and a synchronizing signal of the sub-sampled luminance signal A color television signal encoding device comprising: means for multiplexing and outputting the sub-sampled color signal in a portion; and receiving and separating a multiplexed signal from the encoding device, and performing sub-sampling by the encoding device. Means for outputting a luminance signal and two color signals in accordance with the respective phases performed; and a frequency of the suppressed carrier color signal obtained by performing interpolation on the luminance signal with a two-dimensional interpolation filter using line correlation. Means for removing the aliasing distortion of the luminance signal folded in the portion of the above, means for performing interpolation on the two color signals, and modulation of the interpolated two color signals with subcarriers to obtain a carrier color signal Means for adding a luminance signal subjected to the interpolation filter processing and the carrier color signal to reproduce a composite color television signal. A color television signal code capable of reproducing a high-quality luminance signal having a frequency higher than half the sub-sampling frequency of the luminance signal without using a band-limiting filter for sub-Nyquist sampling on the transmission side. Decryption device.