JP2788733B2 - Color television signal processing method and circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION Technical Field The present invention relates to a system for processing a color television signal containing amplitude-modulated color information.

A composite color television signal (eg, PAL or N
TSC) is not suitable for encoding with one-way or two-way high-efficiency conversion. However, one-way high-efficiency conversion means that only compression is performed, and bidirectional high-efficiency conversion means that both compression and decompression are performed.

In fact, one-way or two-way conversion is
It can be applied to TV signals, but in this case there are two disadvantages:-the energy is spread to higher frequencies when converting the baseband signal-the size (number of pixels) of the conversion block Constraints arise or lack of correlation between the structure of the image and the blocks to be transformed.

This type of composite signal is represented by the following equation.

s (t) = y (t) + c1 (t) × COS (2PI × Fsc × t) + c2 (t) × SIN (2PI × Fsc × t) (1) where y (t) is a luminance signal c1 (t) c2 (t): color signal PI: pi Fh: horizontal synchronization frequency Fsc: color subcarrier frequency (PAL: (1135/4 + 1/625) × FhNTSC: 455/2 × Fh) In this case, the signals y, c1, and c2 are constant, but the signal s (t) is not. This is because the modulation produces an AC component.

As a result, when the transform (image compression) is applied to the composite signal, a large number of non-zero coefficients (high-frequency components) are generated even for a flat image, and the compression efficiency is determined by the baseband signal y (t), It is much lower than the case of c1 (t) and c2 (t).

This problem can be solved by inserting a demodulator between the signal source and the converter. This improves compression efficiency, but significantly degrades image quality and increases costs due to the need for demodulation and remodulation circuits.

Therefore, the present invention is suitable for receiving a composite signal at an input unit and further performing a conversion process (image compression). Further, the component signal y (t), c1 (t), c2 (t)
It is an object of the present invention to provide a processing system for supplying three signals having the same statistical characteristics to the output unit.

The invention also provides the advantage that the system can process incoming composite or component signals in a substantially different manner.

[Embodiment of the Invention] Fig. 1 shows that an analog signal (SAI) is supplied to a block 1 comprising a variable clock generator and an A / D converter, and the output (signal 1 ') of the A / D converter is digital. The digital processing device PRO supplies the processed signals py, pc1, and pc2 to the processing device PRO.
FIG. 1 shows a block diagram of a processing system according to an embodiment of the present invention, as provided to the system.

Therefore, the processing system according to the present embodiment includes the following two parts. That is, the first part in which A / D conversion is performed by adapting a critically variable sampling frequency (1) The input signal thus sampled through a fully considered process is characterized by the characteristics of the signals y, c1, c2 Second part (2) converted into three signals py, pc1 and pc2 having the same statistical properties as (2) By performing the processing reverse to the processing of this part of the processing system of the present invention, the composite signal is completely It will be evident hereafter that it is recoverable and does not introduce errors and therefore does not degrade the quality of the signal.

First Part According to the present embodiment, the sampling clock ck (t) of the analog signal SAI must adhere to two main conditions.

a) N × Fsc where the frequency of the signal is N as an integer
Must be in (or very close to)

b) An integer multiple of the number of samples per unit of conversion employed by this clock must be generated on one line.

A general solution that satisfies conditions a) and b) above is 2
The use of two different sampling frequencies, ie, the frequency for the effective image area of the video signal and the frequency for the line synchronization part, for one component of the composite signal, adapted to Nyquist conditions.

For clarity, the PAL signal is taken as an example (FIGS. 2a, 2
b).

In the A / D converter 11 (FIG. 2b), the PAL signal is a function of the signal spectrum content and is sampled with the variable frequency clock ck (t) obtained by the circuit of FIG. 2b, the spectrum containing a lot of energy In the effective pixel area, the sampling clock ck (t) reaches the maximum frequency ckmax.

In the line blanking region (section), ck (t) has the lowest frequency ckmin. However, the Nyquist condition is satisfied at any sampling frequency.

Therefore, for example, the number of samples (in this case, for example, 1120) which is an integral multiple of the conversion block size (for example, 8) can be obtained per line. Clock Master C (Fig. 2b
Has a frequency of 2270 × Fh, for example.

The variable frequency sampling clock ck (t) is composed of a control signal generator 12 and a sequence network.
It is generated by the circuit shown in 2b. The sequence network consists of flip-flops 3A and 3B, NAND circuit 3C, and OR circuit 3D
It is composed of The circuits configured in this way cooperate with each other to generate a variable frequency sampling clock ck (t) having a frequency of 1/2 or 1/3 of the frequency of the input signal.

FIG. 4A shows a waveform at each point of the circuit shown in FIG. 2B when the frequency of the variable frequency sampling clock ck (t) is half the frequency of the input signal. The frequency is 1 / frequency of the input signal
FIG. 4B shows the waveform at each point of the circuit shown in FIG.

For each scan line, the circuit shown in FIG.
It generates 1090 clock strokes at max (equals 2270 × Fh / 2) and 30 clock strokes at the lowest frequency ckmin (equals 2270 × Fh / 3), for a total of 1120 clock strokes.

The control circuit 12 of FIG. 2b is shown in detail in FIG. 2a. This control circuit includes a counter 4, a decoder 5, a flip-flop 6c, and gates 6A and 6B.

The circuit 12 is dependent on the synchronizing signal of the television signal (external synchronizing signal ES) in phase relation.

The following operation is performed to match the phase of the counter 4 with the signal ES. Conventionally, a rising edge is generated by a circuit that extracts the horizontal frequency in response to a certain position of a video line (one scan line).

Since the rising edge is subject to jitter, it is more customary to pre-scan the time slots in which the rising edge must be.

When the counter 4 is phase locked to the signal ES, a control signal CO is generated at the output of the flip-flop 6C.

As described above, in this embodiment of the invention, this consists of a counter (modulo 1120) of 1120 (block 4) and a pulse of one clock width when the value of the counter reaches "30". This is performed by the circuit shown in FIG. 2A, which comprises an output decoder 5, two gates 6A and 6B, and a flip-flop 6C.

FIG. 5 shows an operation timing chart of the circuit shown in FIG. 2a.

In an embodiment, the sampling frequency ck (t) selected for the effective pixel area of the composite signal is very close to 4 × Fsc, so the resulting sample is given by: s (KT) = y (KT) + u (KT) × COS (2PI × Fsc × KT) + v (KT) × SIN (2PI × Fsc × KT) (2) where T = 1 / (1135 × Fh), The usual notation of the modulated PAL signal was used. That is, c1 was changed to u and c2 was changed to v.

 Expression (3) is obtained by substituting the value of Fsc.

s (KT) = y (KT) + u (KT) × COS (K × PI / 2 + K × 2PI / (1135 + 625)) + v (KT) × SIN (K × PI / 2 + K × 2PI / (1135 + 625)) (3) Second part The system input signal SAI of FIG.
Even when the signal is an AL signal, the signals py, pc1, and pc2 can be obtained from Expression (3).

The processing device PRO of FIG.
Process 1, s2, s3, s4.

py1 = s1 + s3 pc1 = s1-s3 py2 = s2 + s4 pc2 = s2-s4 (4) Phase k × 2PI / (1135 × 625) in the trigonometric function of equation (3)
If there are no errors (considered to be negligible) due to, the py signal (py1 and py2 signals) is proportional to the average of the signal y (t) and the pc signal (pc1 and pc2 signals) Determine the amplitude and phase.

This processing method is repeated for the subsequent four samples.

Since the signals py (py1 and py2) are proportional to the average of the signals y (t), the signals py have the same characteristics as the spectrum of the luminance signal as the component signals, and there are few errors due to the aliasing of the chrominance signals. The signals pc1 and pc2 have spectral characteristics that are linearly proportional to the intensity of the color components (u and v in the case of the PAL signal) of the component signal. this is,
This is because sampling is performed in consideration of the frequency of the color subcarrier. Therefore, signals py, pc1, pc2 are signals y, c1, c2
Will have the same statistical properties as As described above, signal processing completely opposite to this can be performed. That is, the same signal as the initial signal (signal SAI) is obtained again at the receiving output terminal according to the following equation.

s1 = (py1 + pc1) / 2 s2 = (py2 + pc2) / 2 s3 = (py1-pc1) / 2 s4 = (py2-pc2) / 2 The PRO circuit shown in the block diagram of FIG. 8-bit registers 1A, 1B, 1C and
1D, four other 8-bit registers 2A, 2B, 2C and 2D, each connected in parallel to one of the registers 1A to 1D, eight inverters I1 to I8, two 8-bit adders 13A and 1
3B, and two 9-bit registers 5A and 5B at the output stage. The inverters I1 to I8 and the 8-bit adder 13B constitute a subtractor.

The NTSC signal processing method is similar to the processing method for the PAL signal. The difference is that the clock master frequency C and 1 /
This is the number of strokes at 2 frequencies and 1/3 frequency. Clock master frequency is 1820Fh, 1/2 frequency and 1
The number of clocks (number of strokes) in one horizontal period at the / 3 frequency is 868 and 28, respectively. Another point to explain is that bidirectional conversion should be realized.
It is necessary to compensate for the phase rotation that occurs every line. PA
For an L signal, the chrominance subcarrier rotates 90 degrees per line,
Furthermore, the sign of the component v is inverted.

As a first phenomenon, the output signals pc1 and pc2 appear alternately, and the output levels alternate. this is,
Before the output signal is sent to the converter 3, it can be corrected by changing the order.

As a second phenomenon, modulation in the vertical axis direction occurs. The effect can be attenuated only by multiplying the signals pc1 and pc2 of some lines by -1. That is, the signals pc1 and pc2 are not inverted on the scanning lines 1 and 2, and
4 and the scanning lines 5 and 6 do not. And repeat this.

In the case of the NTSC signal, the phase rotation from one scanning line to the next scanning line is 180 degrees, so that pc1 and pc1 for each scanning line are used.
Compensated by multiplying 2 by -1.

[Brief description of the drawings]

FIG. 1 is a system block diagram. FIG. 2a is a block diagram of a control signal generator. FIG. 2b is a diagram of a variable frequency generator and an A / D converter for a PAL signal. FIG. 3 is a block diagram showing the internal configuration of the PRO digital processing device shown in FIG. FIG. 4 is a timing chart for explaining the operation of the variable frequency generator shown in FIG. 2b. FIG. 5 is a timing chart for explaining the operation of the control signal generator shown in FIG. 2a.

Continuation of the front page (72) Inventor Roberto Peruta BGS-24036 Ponte S. Italy. Pietro, Via Avogadro 7 (58) Fields studied (Int. Cl. ⁶ , DB name) H04N 11/04

Claims (6)

(57) [Claims] 1. A method for processing a composite color television signal having color information consisting of amplitude-modulated color signals c1 and c2 and a baseband component consisting of a luminance signal y, comprising: (A) A / D-converting the composite color television signal with a variable frequency sampling clock ck (t) to encode a plurality of the composite color television signals. of generating a sample of (b) 1 the so that the number s _n of the plurality of samples in the horizontal scanning period is an integral multiple of the block size in the conversion of the plurality of sample sampling clock ck (t) Selecting the variable frequency; and (c) circulating the plurality of samples by numerical operation. By performing to the conversion, the plurality of samples,
Each has a correlation with the luminance signal y and the chrominance signals c1 and c2, but each has a correlation with the luminance signal y and the chrominance signal c1.
And a pseudo-luminance signal py different from c2 and a pseudo-color signal pc1
And converting to pc2. A method of processing a composite color television signal, comprising: 2. A composite color television signal processing method according to claim 1, wherein the color television signal (SAI) to be processed is encoded by amplitude modulation of a baseband component and one or more baseband signals. And a band-pass component obtained by
The color television signal (SAI) is sampled at a sampling frequency that is an integral multiple of the frequency of the carrier wave of the amplitude modulation, and the plurality of samplings obtained by the sampling are added and subtracted to obtain three baseband signals. And a composite color television signal processing method. 3. A composite color television signal processing method according to claim 2, wherein said variable frequency of said sampling clock ck (t) is always at least twice the band of said color television signal. A composite color television signal processing method. 4. A composite color television signal processing method according to claim 3, wherein said variable frequency of said sampling clock ck (t) has only two kinds of predetermined values. Signal processing method. 5. A composite color television signal having color information comprising amplitude-modulated color signals c1 and c2 and a baseband component comprising a luminance signal y, and processing the composite color television signal by unidirectional or bidirectional conversion. A processing circuit comprising means for encoding a composite color television signal, comprising: (a) A / D converting the composite color television signal by a sampling clock ck (t) having a variable frequency, means for generating a plurality of samples, (b) 1 the so that the number s _n of the plurality of samples in the horizontal scanning period is an integral multiple of the block size in the conversion of the plurality of sample sampling clock ck (t) Means for selecting said variable frequency; and (c) periodically selecting said plurality of samples by numerical operation. By performing the conversion, the plurality of samples,
Each has a correlation with the luminance signal y and the color signals c1 and c2, but each has a correlation with the luminance signal y and the color signal c1.
And a pseudo-luminance signal py different from c2 and a pseudo-color signal pc1
And a means for converting into a pc2. A composite color television signal processing circuit, comprising: 6. The composite color television signal processing circuit according to claim 5, further comprising at least one variable clock generating means, an A / D converter, and a digital processor (PRO). PRO) has four cascade registers (1A, 1B, 1C, 1D) and four registers of the second type (2A, 2B, 2C, 2C) each connected in parallel with one of the four cascade registers.
D), eight inverters (I1 to I8) connected to two of the four registers of the second type, two adders (13A, 13B), and each of the two adders And two output registers connected to each other.
Connected directly to all of the two second type registers, the other directly connected to two of the four second type registers, and via the remaining two of the four second type registers and the eight inverters A composite color television signal processing circuit, which is connected.