JP3444078B2 - Video signal processing apparatus and video signal processing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a video tape recorder for recording an analog video signal from a video disc, a digital VCR, a digital broadcast receiver, and the like, and a television receiver for displaying the reproduced output thereof. Video signal processing device and video signal processing
Regarding the method of treatment.

[0002]

2. Description of the Related Art With the development of digital technology, it is becoming easy to obtain high-quality video signal sources even at home. For example, not only pre-recorded tape (soft tape) but also digital broadcasting terminals, DVD
(Digital Video Disc) and the like provide high-quality video signals to users. Digital VCRs (video cassette tape recorders) are gradually becoming popular for home use, but at present, analog VCRs are remarkably prevalent. From the standpoint of copyright protection, providers of high-quality video signals as described above have to pay a great deal of attention to the restriction of copying by the analog VCR.

In the analog VCR, some copy restriction methods have already been considered. For example, the AGC pulse method and the color stripe method by Macrovision are known. In the AGC pulse system, when copying is prohibited, a pulse having a level higher than the normal AGC reference level is inserted into the AGC reference level detection section of the video signal to limit the copy. That is, the pseudo SYNC pulse is inserted in a part of the V (vertical) blanking period of the video signal. For example, as shown in FIG. 9A, a pseudo sync pulse is inserted in a part of the V blanking period of the video signal. FIG. 9B is an enlarged view showing a portion where the pseudo sync pulse is inserted. This pseudo sync pulse is inserted by, for example, 5 waves at a level obtained by adding the level p to the horizontal sync pulse. Also, this level p is changed and inserted.

Analog VCR (home analog VCR)
Then, 1H in the V blanking period shown in FIG. 9C.
There are many models adapted to apply AGC by using the horizontal synchronizing pulse. Therefore, when a pseudo sync pulse having an amplitude larger than that of the horizontal sync pulse is inserted into 1H in this way, the AGC circuit determines that the amplitude of the pseudo sync pulse is the reference level and performs AGC. as a result,
Since the AGC level is detected as the level of this pseudo sync pulse, the sync signal cannot be detected by amplitude separation, and normal reproduction cannot be performed. On the other hand, since the television monitor has a different AGC system, it is possible to display the reproduced image normally.

However, in this AGC pulse system, V
There is a problem that it is effective only for a part of the HS system video tape recorders. For example, β-type VCR or 8
Even in the mmVCR and VHS systems, there was no effect on those having a long AGC time constant.

Therefore, as another copy restriction method, the color stripe method described below has been proposed.
The color stripe method is a method of inverting the phase of the entire burst signal by, for example, 2 to 4 lines for every 20 lines with respect to the reproduced video signal. When the reproduced video signal with the phase of the burst signal thus inverted is recorded by another home analog VCR, the APC (automatic phase control circuit) of the analog VCR uses the burst signal with the inverted phase as the original burst signal. Since it is used, the color of the line is inverted and recorded / reproduced. Therefore, when this recorded video signal is reproduced, as shown in FIG. 10, bands of reversed colors are displayed on the screen every 20 lines.

On the other hand, in a general television receiver, a PLL (A) that forms a carrier wave for color signal demodulation is used.
Since the time constant of (PC) is long, even if the burst signal is continuously inverted in 2 to 4 lines at most, there is no effect. However, depending on the model, there is a case where a PLL having a short time constant is used, and in this case, there is a problem in that a band in which colors are reversed appears on the screen.

Further, the applicant of the present application has proposed a copy limiting method for inverting the phase of a part of the period of the color burst signals of all lines in the effective screen. This method has an advantage of not causing such a problem even in a television monitor in which the image quality of a display image is deteriorated in the color stripe method described above.

In an analog home VCR,
A color subcarrier having a frequency of 3.58 MHz (in the case of the NTSC system) is low-pass-converted into a low-pass conversion color signal having a predetermined center frequency within 600 to 700 KHz.
Then, the low-frequency converted color signal and the luminance signal are frequency-multiplexed and recorded on the magnetic tape. As described above, the color signal in the home-use analog VCR is very narrowly band-limited and recorded on the magnetic tape as compared with a television receiver or the like.

Therefore, when reproduced, the color burst signal contained in the recorded video signal has the property of being expanded before and after the original signal before recording on the time axis due to band limitation. Have. FIG. 11 shows a color burst signal in the original signal and the signal after being reproduced by the VCR.
When the original signal a of the color burst signal arranged after the horizontal synchronizing signal h shown in FIG. 11A is recorded and reproduced on the magnetic tape, as shown in FIG. 11B, the color burst signal a moves back and forth on the time axis. To be extended.

A method of utilizing this property to prevent copy is a method of inverting a part of the phase of the burst signal.
FIG. 12A shows a normal color burst signal a. On the other hand, FIG. 12B is an example in which the pseudo burst signal b (indicated by diagonal lines) with the phase inverted is inserted behind the normal color burst signal a. Further, FIG. 12C shows the original signal a.
3 is an example of a copy protection signal in which a pseudo burst signal b is inserted on the front side of FIG. Further, FIG. 12D shows an example of a copy protection signal in which pseudo burst signals b and c are inserted before and after the original signal a. For example, when the pseudo burst signals b and c are inserted before and after the original signal a for a color burst signal having nine waves, for example, two waves are inserted respectively before and after the original signal a, and the phases thereof are inverted from the original phases. .

When the video signal to which the copy protection signal including the pseudo burst signals b and c is added is recorded and reproduced as described above, the original signal of the color burst signal is obtained in accordance with the above-described extension of front and back on the time axis. The width of the pseudo burst signals b and c added before and after a is increased. This state is shown in FIG. That is, in the copy protection signal in which the pseudo burst signals b and c shown in FIG. 13A are inserted, the pseudo burst signals b and c have a width as shown in FIG. 13B after being recorded / reproduced on / from the magnetic tape. Expanded back and forth.

The video signal including the copy protection signal having the increased width is VCR when reproduced by VCR, for example.
The PLL cannot follow in the color synchronizing circuit of (1), which causes deterioration of the image, and thus copy can be prevented. Of course, even if this video signal is recorded / reproduced by another VCR, a normal image cannot be obtained.
Needless to say.

On the other hand, the video signal shown in FIG. 13A including the copy protection signal in which the pseudo burst signals b and c are inserted before and after the color burst signal is detected as a substantially regular color burst signal on the television monitor. used. Therefore, in this case, image deterioration does not occur.

[0015]

As described above, the method proposed by the applicant of the present application, which restricts copying by partially inverting the phase of the color burst signal, has a frequency band of the color signal of the VCR. Since the narrowness is used, there is an advantage that there is little interference with the television monitor. However, an analog VC with a wide color signal band
For R (S-VHS etc.), there is a problem that the copy protection effect is insufficient.

[0016] Therefore, an object of the present invention, the television less interference to display by the monitor, and the copy protection effect can be a reliable video signal processing apparatus 及
And a video signal processing method .

[0017]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is a video signal processing apparatus for limiting recording of a video signal for analog output from a video signal source. It has means for making the frequency of the color burst signal in the video signal different from the normal frequency, so that the television monitor can normally reproduce the output analog video signal, while
This is a video signal processing device characterized in that the reproducing device cannot normally record / reproduce the output analog video signal.

[0018]

Furthermore, the present invention is a video signal processing method for limiting recording of a video signal for analog output from a video signal source, wherein the frequency of a color burst signal in the output analog video signal is a normal frequency. And a step of setting the frequency to be different from that of the television monitor so that the television monitor can properly reproduce the output analog video signal, while the video signal recording / reproducing device cannot properly record / reproduce the output analog video signal. And a video signal processing method.

[0020]

The frequency of the color burst signal in the analog video signal is different from the normal frequency. When the analog VCR records / reproduces such an analog video signal, the image quality of a reproduced image deteriorates, whereby copy restriction is achieved. On the other hand, when such an analog video signal is supplied to the monitor device, the monitor device can see a normal image without causing image quality deterioration. Even in the case of a VCR having a wide band of color signals, a reliable copy protection effect can be achieved.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. To facilitate understanding of the present invention, an application example of copy restriction will be described with reference to FIG. Figure 1
Is an example in which an analog video signal reproduced by the digital VCR 2 is recorded by the analog VCR 1. The cassette tape reproduced by the digital VCR 2 is, for example, a pre-recorded tape, and control information (CGMS) regarding the copy generation limitation recorded in the tape is used.
(Referred to as “Copy Generation Management System”) instructs to prohibit copying, it is necessary to prohibit recording by the analog VCR 1.

FIG. 1B shows an example in which the reproduced analog video signal from the DVD player 3 is recorded by the analog VCR 1. Even in this case, the CGM recorded on the DVD
If S prohibits copying, analog V
Recording by CR1 needs to be prohibited. Further, FIG. 1C shows an IRD (Integeg) for receiving digital broadcasting.
Program received by rated receiver decoder (or set top box) 4 is digital VCR
Recorded by 5 and recorded contents by analog VCR1
This is an example of recording by. Generally, the digital VCR 5 is often permitted to record a digital broadcast program as a digital signal or an analog signal once. However, copying the recorded contents by the analog VCR 1 is limited. Of course, copying of the video signal from the IRD 4 to the analog VCR 1 may be prohibited.

The present invention prohibits copying by the analog VCR 1 in the case as illustrated in FIG. 1, and the digital VCR 2, the DVD player 3, the digital VCR.
It is possible to display the analog video signal from the monitor 5 on the monitor device without any trouble. FIG. 2 shows an embodiment of the present invention applied to the case of outputting an analog video signal reproduced by the DVD player 3 as in the example of FIG. 1B.

A digital signal compression-coded by MPEG or the like is read from the DVD 6 by the optical pickup 7. The reproduction signal of the optical pickup 7 is supplied to the error processing circuit 9 via the preamplifier, the waveform shaping and decoding circuit 8. In the error processing circuit 9, the error correction code is decoded and the error is corrected. The output of the error processing circuit 9 is supplied to the demultiplexer 10. The demultiplexer 10 separates video data, audio data, and control digital data from the reproduction signal.

The video data is supplied to the video decoder 11. The video decoder 11 performs processing such as decoding of compression encoding and conversion into an analog video signal, and supplies the analog video signal to the output unit 14. This output unit 1
4 is the one to which the present invention is applied, the details of which will be described later. An analog video signal to which a copy protection signal is selectively added is output from the output unit 14 to the output terminal 16. In the audio decoder 12, the audio data is subjected to processing such as decoding of compression encoding and conversion into an analog audio signal, and an analog audio signal is obtained at the output terminal 17. The digital data decoder 13 separates and decodes the control digital data recorded on the DVD 6. CGMS is included in this control digital data, and a copy control signal is formed based on this CGMS. A copy control signal is given to the output unit 14. The output unit 14 is provided inside the DVD player.

An example of the structure of the output unit 14 is shown in FIG. The reproduced video signal from the video decoder 11 is supplied to the output unit 14 as, for example, an analog component signal. A luminance signal (including a synchronization signal) Y, a color difference signal RY, and an input terminal denoted by reference numerals 21, 22, and 23,
BY is supplied respectively. The luminance signal Y is added by the adder 24
Through the output terminal 16Y. The color difference signal is supplied to the color encoder 25, and a carrier color signal (including a color burst signal) that is quadrature two-phase modulated is formed by the color encoder 25. The carrier color signal from the color encoder 25 is supplied to one input terminal a of the switcher 26. The switcher 26 is provided for replacing the color burst signal. The output of the switcher 26 is taken out to the output terminal 16C.

In one embodiment of the present invention, in order to secure the effect of copy protection more securely, a copy protection signal whose frequency deviates from the normal frequency is inserted in place of the color burst signal, and the above-mentioned AGC. The pulse method is used together. This copy protection signal is inserted at the same timing as the regular color burst signal, and can be called a pseudo color burst signal. The adder 24 is supplied with the AGC pulse from the AGC pulse generator 28 and adds the AGC pulse to the luminance signal Y. The AGC pulse generator 28 generates one of a normal level and a high level for inhibiting copying as the AGC pulse. The selection is made by the data decoder 1
3 (see FIG. 2) from the copy control signal supplied to the input terminal 36.

The color burst signal supplied to the input terminal b of the switcher 26 is output from the switcher 27. The switcher 26 is the timing controller 3
5 output. That is, in the case where the copy permission is instructed by the copy control signal,
The input terminal a is always selected and the color burst signal is not replaced. On the other hand, when the copy control signal instructs to prohibit copying, the input terminal b is selected in a period slightly wider than the period of the color burst signal, and the color burst signal is replaced. Therefore, when the video signal taken out to the output terminals 16Y and 16C is recorded by the analog VCR, the recording can be prohibited. As described above, the control mode of the switcher 26 is different depending on permission / prohibition of copying, so that the timing controller 35 is supplied with the sync signal separated by the sync separation circuit 34 and the copy control signal from the input terminal 36. It

The input terminal c of the switcher 27 is supplied with a color burst signal SB1 generated by the signal generator 31 and having a regular color subcarrier frequency f _s (3.58 MHz in the NTSC system). The input terminal d of the switcher 27 is supplied with the copy protection signal SB2 of the frequency (f _s + f _m ) generated by the signal generator 32,
The input terminal e of the switcher 27, generated by the signal generator 33, the frequency (f _s -f _m) copy protection signal S
B3 is supplied. As the frequency shift f _{m with} respect to the regular frequency f _s , any frequency can be selected, but here it is selected to be an integral multiple of the horizontal scanning frequency f _h , for example, 4 times (4f _h ).

Although not shown, the color burst signal S having a regular frequency generated by the signal generator 31.
B1 has a fixed phase relationship with the color subcarrier signal used in the color encoder 25, like the regular color burst signal. Therefore, the signal generator 31
It is also possible to replace the color burst signal only with the line to which the copy protection signals SB2 and SB3 are added without providing the above. Further, in the configuration of FIG. 3, the luminance signal Y includes a sync signal and the color encoder 25 generates the color burst signal. However, a circuit for generating the sync signal and the color burst signal is provided, and the generated sync signal and The color burst signal may be added to each of the luminance signal and the carrier color signal.

FIG. 4 shows an example of a mode for adding a copy protection signal according to the present invention. When the copy inhibition is instructed by the copy control signal, the color burst signal is replaced with a cycle of 20 lines as shown in FIG. For each of the first 14 lines of the 20 lines, the color burst signal S of regular frequency
B1 is added. Copy protection signals SB2 and SB3 are alternately added from the 15th line to the 20th line. In the cycle of the next 20 lines, the color burst signal is similarly replaced.

FIG. 5 shows specific waveforms of the color burst signal SB1 and the copy protection signal, for example, SB3. A color burst signal SB1 having eight cycles of a sine wave is inserted in the back porch of the horizontal synchronizing signal HD. Copy protection signal SB3 are the frequency (f _s -f _m), when the number of cycles is inserted equal, burst signal period is slightly longer. Although not shown, the copy protection signal SB2 are the frequency (f _s + f _m), when the number of cycles is inserted equal, burst signal period is slightly shortened.

As described above, in one embodiment of the present invention, the copy protection signal in which the frequency of the color burst signal is shifted from the regular frequency is inserted. This amount of frequency deviation causes less interference with the television monitor, and the video signal recording / reproducing device (more specifically,
It is selected to such an extent that the low-frequency conversion carrier generation circuit of the analog VCR) malfunctions. As a specific example, in the case where a copy protection signal is inserted in several continuous lines (more specifically, 3 to 8 lines), several tens of kHz (with respect to the regular color subcarrier frequency f _s ( More specifically,
It has a deviation of 50 to 60 kHz).

When an analog video signal whose frequency is different from the normal one is supplied to the monitor,
Since the time constant of the APC of the monitor is relatively long, it does not hinder the generation of color subcarriers for color demodulation.
You can see normal color images. On the other hand, in the analog VCR, the subcarrier of the carrier color signal is frequency-converted into a low frequency carrier frequency. Therefore, the color burst signal is separated, and the separated color burst signal is supplied to the conversion carrier signal generation circuit having the PLL structure. If the frequency of the color burst signal deviates from the normal one, the conversion carrier generating circuit may not be locked or malfunctions, and the generated conversion carrier signal also deviates in phase or frequency from the normal one. . Since the low-frequency conversion is performed by such a conversion carrier, the phase of the low-frequency conversion color signal recorded on the tape becomes out of phase with the normal one and, in some cases, the inverted phase. Therefore, even if the signal recorded in this way is reproduced, a normal reproduced image cannot be seen, and similar to the color stripe system described above, a band-shaped area in which the color is not correct appears in the reproduced screen. In this way, copy protection can be performed. Since the present invention does not utilize the narrow band of the color signal in the analog VCR, even if the analog VCR is a wide band VCR such as S-VHS, the copy protection effect is not impaired.

In the above example, the copy protection signal is inserted with a cycle of 20 lines, and the color becomes abnormal every 20 lines in the reproduction screen. Therefore, at what interval the band with the abnormal color is produced can be appropriately set depending on the length of the cycle. Further, in the above-described embodiment, the frequency shift between adjacent lines is symmetric, such as ± f _m . As a result, it is possible to eliminate an average frequency deviation between adjacent lines, and the AP of the television monitor can be eliminated.
It is possible to reduce the adverse effect on C. Further, as in the above-described embodiment, by selecting this frequency shift to be an integral multiple of the horizontal scanning frequency f _h , the copy protection signal can be locked in the horizontal scanning. As a result, it is possible to prevent the interference generated by erroneously processing the copy protection signal as the luminance signal from flowing on the screen, and make this interference inconspicuous. Furthermore, the direction of frequency shift is not limited to adjacent lines, but may be opposite for each frame.

FIG. 6A shows an example of CGMS prerecorded in association with the digital video signal recorded on the DVD 6. As shown in FIG. 6A, CGMS is defined as follows. 00: Copy is possible 01: Not used 10: Copy one generation is possible 11: Copy is not possible

When the copy in this CGMS defines only digital copy restriction, a flag indicating whether analog copy is possible, that is, a trigger bit for instructing generation of an analog copy restriction signal may be specified separately.
FIG. 6B is an example of the case. If the trigger bit is “0”, it is instructed not to generate the analog copy limit signal, and if this bit is “1”, the analog copy limit signal is generated. Is instructed. In this case, C
With a total of 3 bits of GMS and trigger bit,
The analog copy restriction information is configured. However, both analog and digital are defined by the CGMS, and the unused 2 bits (01) of the CGMS are used to generate the analog VC with 2 bits.
The copy restriction information by R may be configured.

Various forms are possible for actually recording such copy restriction information on a recording medium.
In the case of a digital VCR, the data structure shown in FIGS. 7 and 8 is adopted. FIG. 7 shows the structure of VAUX (video auxiliary data), which is (01100001) (6
1h) (h indicates hexadecimal display) is a pack having a pack header.

In this pack, CGMS is recorded as the upper 2 bits of PC1. The definition of this CGMS is
For example, it is the same as that shown in FIG. 6A. Also, the copy source in the PC 1 is defined as follows. 00: Copy by analog input 01: Copy by digital input 10: Reserve 11: No information

The definition of the copy generation in PC1 is shown below. 00: 1st generation 01: 2nd generation 10: 3rd generation 11: 4th generation

FIG. 8 shows an example of auxiliary data (AAUX data) relating to an audio signal in a digital VCR. The header of this pack is (01010001)
(51h). In this pack PC1, information on copy generation restriction is recorded in the same configuration as VAUX. When the CGMS associated with the input video signal is copyable for one generation and the input video signal is recorded, the CGMS on the tape is rewritten to copy prohibited.

In the case of the DVD according to the embodiment of the present invention, although not shown, the recording data has a division such as a sector, and the synchronization signal and the header are added to the head of this division. Information for copy restriction is recorded in this header.

In the configuration of FIG. 3, the normal burst signal SB1, the first and second copy protection signals SB2,
Although the generation circuits of SB3 are shown as separate blocks, as described above, in the case where the amounts of deviation with respect to the normal frequency are made equal and the direction is switched, some hardware of these generation circuits is used. It is possible to share. A frequency modulation circuit, a frequency conversion circuit, or the like may be used as a configuration for making the frequencies of the color burst signals different. Furthermore, in the present invention, the copy protection signal may be added to the composite signal format in which the luminance signal and the carrier color signal are superimposed, instead of the component signal format.

[0045]

As described above, according to the present invention, copying is prevented by making the frequency of the color burst signal different from the normal one, so that even in the case of a wide band video signal recording / reproducing apparatus, the certainty can be ensured. Copying can be prevented. Further, according to the present invention, since the information for instructing the copy restriction is recorded together with the digital video signal in the recording medium such as the pre-recorded tape and the DVD, the copyright recorded in these recording media is protected. It can be surely protected.

[Brief description of drawings]

FIG. 1 is a block diagram showing some examples of a video signal recording system to which the present invention can be applied.

FIG. 2 is a block diagram of an embodiment in which the present invention is applied to the case of recording a reproduced analog signal of a DVD player.

FIG. 3 is a block diagram of an output unit to which the present invention is applied.

FIG. 4 is a schematic diagram for explaining an example of a mode in which a copy protection signal is added.

FIG. 5 is a schematic diagram showing a waveform of an example of a copy protection signal.

FIG. 6 is a schematic diagram used to describe an example of CGMS and a trigger bit for instructing generation of a copy limiting signal.

FIG. 7 is a CG used in a digital VCR.
FIG. 6 is a schematic diagram used to describe an example of a recording method of MS.

FIG. 8 is a CG used in a digital VCR.
FIG. 6 is a schematic diagram used to describe an example of a recording method of MS.

FIG. 9 is a waveform diagram for explaining the AGC pulse system. FIG. 9 is a waveform diagram showing that the width of the copy protection signal has increased after reproduction.

FIG. 10 is a schematic diagram for explaining a color stripe system.

FIG. 11 is a waveform diagram showing a color burst signal in an original signal and a color burst signal after reproduction.

FIG. 12 is a waveform diagram showing some examples of copy protection signals proposed previously.

FIG. 13 is a schematic diagram for explaining a copy protection operation using a copy protection signal that has been previously proposed.

[Explanation of symbols]

6 ... DVD, 14 ... Output section for outputting reproduced analog video signal, 16, 16Y, 16C ... Output terminal, 24 ... Adder, 26, 27 ... Switcher, 31. ..Signal generators that generate regular burst signals, 32, 33 ... Signal generators that generate copy protection signals

Claims (10)

(57) [Claims] 1. A video signal processing device for limiting recording of a video signal for analog output from a video signal source, wherein the frequency of a color burst signal in the output analog video signal is different from a regular frequency. , Which allows the television monitor to normally reproduce the output analog video signal while the video signal recording / recording
The playback device normally records / records the output analog video signal.
A video signal processing device characterized in that reproduction is prohibited. 2. The apparatus according to claim 1, wherein the frequency of the color burst signal is different from the regular frequency when the copy generation restriction information associated with the analog video signal indicates a copy prohibited state. Video signal processing device characterized by: 3. The video signal processing device according to claim 1, wherein the frequency of the color burst signal for several lines is different from the regular frequency for every predetermined number of lines. 4. The video signal according to claim 1, wherein the frequency of the color burst signal is different from the regular frequency so that the frequency is alternately changed for every adjacent line. Processing equipment. 5. The apparatus according to claim 4, wherein when the frequency of the color burst signal is different from the regular frequency so that the frequency is alternately changed for each adjacent line, the color subcarrier frequency is changed. To be symmetrical,
A video signal processing device characterized in that the frequency is shifted by ± f _m . 6. A video for analog output from a video signal source.
With video signal processing method to limit the recording of video signal
Frequency matching, the color burst signal in the output analog video signal
The step of causing the number to differ from the normal frequency so that the television monitor can
The video signal can be re-live normally, on the other hand, the video signal recording /
The playback device normally records / records the output analog video signal.
Video signal processing characterized by being disabled for playback
Reasoning method. 7. The method according to claim 6, wherein copy generation restriction information associated with the analog video signal is
The color burst signal of the above
The feature is that the frequency is different from the regular frequency.
Video signal processing method. 8. The method according to claim 6, wherein a color burst signal for several lines is provided for every predetermined number of lines.
The feature is that the frequency is different from the regular frequency.
Video signal processing method. 9. The method according to claim 6, wherein the frequency is alternately changed for every adjacent line.
Differentiate the frequency of the Lar burst signal from the normal frequency
A video signal processing method characterized by the above. 10. The method according to claim 9, wherein the frequency is alternately changed for every adjacent line.
Differentiate the frequency of the Lar burst signal from the normal frequency
In order to be symmetric with respect to the color subcarrier frequency,
The feature is that the frequency is shifted by ± f _m.
Video signal processing method.