JPH08265802A - Signal compressor and signal expander - Google Patents

Abstract

PURPOSE: To obtain a video signal by compressing left/right video signals to obtain a stereoscopic image without missing. CONSTITUTION: A right eye signal and a left eye signal are subject to time base compression by time base compression 23R, 23L respectively. The left/right both ends within 1H of each signal are compressed by A/D converters 201R, 201L and memories 202R, 202L at a high compression rate and the middle part is compressed at a lower compression rate by A/D converters 27R,27L and memories 28R, 28L. Two compression signals are arranged in front and in rear position within 1H by an adder 24 and a reference pulse is inserted between the two signals and the result is outputted as a compressed video signal. A control section 20 provides clocks fc, 2fc, 4fc to each A/D converter and each memory and provides write/read timing pulses WE1, WE2, and OE1-OE4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal compression device and a signal decompression device used when recording and reproducing image signals of two systems such as a stereoscopic image.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a conventional stereoscopic image signal recording / reproducing apparatus. The brightness signal will be described below. When recording, the left and right cameras 1 of the compound eye camera 1
The signals R and L including the two-system synchronization signals shown in FIG. 6A, which are output from 1R and 11L, are input to the mixing circuit 2 in order to convert them into one signal. Are these signals R and L synchronized with one of the signals?
Alternatively, synchronization is achieved by a synchronization signal from another synchronization signal generation circuit.

FIG. 7 shows the structure of the mixing circuit 2. In FIG. 7, the sync separation circuit 21 takes out a sync signal from a signal serving as a reference for synchronization, here, a right-eye signal R, and removes the sync signal from each signal by subtractors 22R and 22L.
The signal shown in FIG. 6B is used. Next, the respective signals R and L are halved in the time axis direction by the time axis compression units 23R and 23L.
6 (c), a signal R'composed of signal components in the first half of one horizontal scanning period and a signal L'composed of signal components in the latter half of one horizontal scanning period are created as shown in FIG. Are added by an adder 24 to generate one luminance signal in which two signals R ′ and L ′ are arranged as shown in FIG. 6D in one horizontal scanning period. Next, the adder 25 adds the synchronization signals and the LPF 26 limits the VTR recording band, for example, 6 MHz in the high band to form the video signal of FIG.
And the like are recorded in the recording / reproducing apparatus 3. This video signal is also applied to the monitor 6.

As a compression method in the time axis compression units 23R and 23L, the input signals are A / D converters 27R and 27R.
After being digitized by L, the signal is sampled with a clock having a frequency fc that is twice the recording band of the VTR, that is, four times or more the maximum frequency of the signal itself, and the memories 28R and 28L are sampled.
To read the signal at the frequency 2fc. The read signal is converted into an analog signal by the D / A converters 29R and 29L. The clock used in the PLL circuit 30 is phase-synchronized with the sync signal or the like obtained from the sync separation circuit 21.

Next, at the time of reproduction, the signals R'and L'reproduced from the VTR shown in FIG. 8 (a) are separated into two signals by the separation circuit 4 and are provided in correspondence to the left and right eyes. It is input to the stereoscopic display device 5 having the right-eye and left-eye display devices 51R and 51L of the system. This stereoscopic display device 5 is, for example, L
It has an image display means such as a CD panel.

FIG. 9 shows the structure of the separation circuit 4, which is the reverse of the mixing circuit. In FIG. 9, the sync separation circuit 41 extracts the sync signal from the reproduced video signal, and the subtractor 42 removes the sync signal to obtain the signal of FIG. 8B. This signal is sent to the switch 43 in FIG.
As described above, the signal is divided into a signal R'of only the signal component in the first half of one horizontal scanning period and a signal L'of only the signal component in the latter half of the one horizontal scanning period.
At 4 L, the time axis is expanded to form the signal shown in FIG.
Next, the adders 45R and 45L add the synchronization signals,
A stereoscopic display device 5 having two systems of luminance signals as shown in FIG.
To enter. Time axis expansion is the opposite of compression, and A / D converter 4
After passing through 6R and 46L, it is sampled at a frequency of 2fc, written in the memories 47R and 47L, read at a frequency of fc, and output through the D / A converters 48R and 48L. In addition, the sample clock is PL
In the L circuit 49, the one that is phase-locked with the input reproduction signal is used.

The above recording / reproducing method is a basic method.
All the signal components of each effective period of the system video signal are mixed at a compression rate of 1/2. On the other hand, it has already been proposed by the applicant of the present invention to insert a reference pulse between the compressed first half signal and the compressed second half signal as in the mixed signal shown in FIG. This reference pulse is used as a reference pulse for time-axis correction for the latter half of the signal during reproduction,
It is also a pulse for left / right discrimination of a stereoscopic signal. In this case, the signal compression rate is set to 1/2 or more, for example, 1/3 as shown in FIG. 9A, or 1 as shown in FIG.
The pulse insertion period is provided by cutting out a part of the signal, for example, the left and right end parts, by setting it to / 2.

[0008]

As in the above-mentioned conventional example,
When the reference pulse as shown in FIG. 10 is inserted between the first half portion and the second half portion of the compressed signal, the required insertion period of the reference pulse is about 5 to 8 μsec in consideration of the jitter in the horizontal scanning period. Conceivable. If the period is shorter than this, a signal may enter the extraction period of the reference pulse, and it may not be possible to accurately extract only the reference pulse. In addition, as shown in FIG. 10, the insertion period is set to 5 μse.
c is the signal-free part before and after the signal is 4.5μ
sec, 1.3 μsec, and the horizontal synchronizing signal section is 4.
If the horizontal scanning period is 5 μsec and one horizontal scanning period is 63.6 μsec, the compression rate needs to be larger than 1 / 2.21 in order to use all the components of the video signal.
Since the compression rate is used again at the time of reproduction, it is usually not 1 which is difficult to reproduce like the above-mentioned 1 / 2.21.
Although it is set to /2.5, 1/3, or the like, if the compression rate is made larger than 1/2, there arises a problem that image deterioration becomes noticeable. Further, if the compression rate is fixed to 1/2 and mixing is performed, under the above conditions, about 10% of the video signal is cut off, which causes a problem that a part of the image signal is lost.

Therefore, the present invention compresses signals of two systems,
A compressed signal is formed by arranging two compressed signals forward and backward with a reference signal in between, and when decompressing this single signal, the two signals are arranged without loss and the reference signal is It is an object of the present invention to obtain a signal compression device and a signal decompression device that can be reliably extracted even when inserted.

[0010]

According to a first aspect of the present invention, there is provided a signal compression apparatus, wherein a plurality of signals are each divided into one or more parts, and the signals of the respective parts are respectively compressed at a predetermined compression ratio and compressed. 1) Arrange the signals of each part in a predetermined order.
It is designed to be output as one signal.

The signal compression apparatus according to the invention of claim 2 is
A compression means for compressing each of the two video signals by changing the compression rate according to its position within one horizontal scanning period, and the two compressed video signals are arranged before and after one horizontal scanning period to form one video image. And output means for outputting as a signal.

According to a third aspect of the present invention, the compression rate of the video signal near the center of the one horizontal scanning period is lowered and the compression rate of the video signal near both ends is increased. According to a fourth aspect of the present invention, one of the two compressed video signals is arranged at a position corresponding to the leading edge portion of the effective image position in one horizontal scanning period, and the other signal is placed at the trailing edge portion. In addition to moving and arranging them in a timely manner, these 2
A reference signal is inserted between two signals to form one signal. According to the invention of claim 5, the time for inserting the reference signal is secured for a predetermined time or more.

According to a sixth aspect of the present invention, the two compressed signals are arranged before and after the remaining period excluding the time for inserting the reference signal, and for the vicinity of the center within the one horizontal scanning period. The signal compression rate is lowered and the signal compression rate near both ends is increased.

According to a seventh aspect of the present invention, in a signal decompressor, a plurality of signals are each divided into one or more, the signals of each part are respectively compressed by a predetermined compression ratio, and the signals of each compressed part are in a predetermined order. The plurality of signals are arranged so as to expand the arrayed signals, expand the signals of the respective compressed parts by an expansion ratio according to the compression ratio, respectively, and rearrange the expanded signals of the respective parts. Is output.

The signal expansion device according to the invention of claim 8 is 2
Each of the two video signals is compressed within one horizontal scanning period by changing the compression rate according to its position, and a video signal formed by arranging the two compressed signals before and after in one horizontal scanning period is input. The two compressed signals are expanded at an expansion rate according to the compression rate, and the two expanded signals are output as two video signals in one horizontal scanning period. It is a thing.

[0016]

According to the invention of claim 1, it is possible to prevent a part of the signal from being lost by appropriately selecting the compression ratio of the signal of each part. According to the invention of claim 2, 1
By properly selecting the compression rate according to the position of the horizontal scanning period, it is possible to prevent a part of the displayed image from being lost.

According to the third aspect of the invention, the deterioration of the image near the center of the screen is reduced by lowering the compression rate of the video signal near the center of the horizontal scanning period and increasing the compression rate of the video signal near both ends. Can be minimized. According to the invention of claim 4, of the two compressed signals which are arranged one after another in time, one signal is arranged at a position aligned with the leading edge portion of the effective image position during one horizontal scanning period. , Place the other by moving it to a position that matches the trailing edge,
By using one signal, the reference signal can be inserted.

According to the invention of claim 5, the reference signal can be extracted without affecting the signal component at the time of expansion by setting the time for inserting the reference signal to be a predetermined time or more, and the image deterioration due to the jitter can be achieved. Can be suppressed. According to the invention of claim 6, in the remaining period excluding the time for inserting the reference signal, the compression rate near the center of one horizontal scanning period is decreased and the compression rate near both ends is increased,
By arranging the two compressed signals before and after the reference signal, the deterioration of the image near the center of the screen is minimized without losing a part of the video signal, and the reference signal is used as a signal component during reproduction. Can be extracted without affecting the image quality, and image deterioration due to jitter can be suppressed.

According to the invention of claim 7, the signals of the respective compressed parts are expanded at respective expansion ratios corresponding to their compression ratios, and the expanded signals of the respective parts are rearranged and output as the plurality of signals. By doing so, it is possible to prevent a part of the plurality of output signals from being lost. Claim 8
According to the invention, the two compressed signals are expanded by the expansion ratio according to the compression ratio, and the two expanded signals are output by outputting two video signals in each one horizontal scanning period. It is possible to prevent a part of the two generated video signals from being lost.

[0020]

1 shows an embodiment of a mixing circuit 2 as a signal compression device according to the present invention. The mixing circuit 2 adds A / D converters 201R and 201L and memories 202R and 202L to the time axis compression units 23R and 23L in the circuit of FIG. 7, and controls the time axis compression units 23R and 23L. The part 20 is provided.

The control unit 20 controls the write enable pulses WE1 and WE as shown in FIG. 2D and the output enable pulse as shown in FIG. Pulse OE1 to OE4
And fc, 2fc, and 4fc are output to control the time axis compression units 23R and 23L. At the same time, the control section 20 outputs the reference pulse P as shown in FIG. The other parts are configured in the same manner as in FIG. 7, and in FIG. 1, parts corresponding to those in FIG.

Next, the operation of the above configuration will be described. At the time of recording, the camera 51 for the left eye and the right eye of FIG.
The signals R and L shown in FIG. 2A obtained from R and 51L have the synchronization signals removed and become the signals in FIG. 2B, which are added to the time axis compression units 23R and 23L and time axis compressed. This compression is performed as follows.

The signals of FIG. 2 (b) are respectively left and right end portions R-1, R-3, L-1, L-3 as shown in FIG. 2 (c).
And the central portion R-2 and L-2 are temporally separated, and R-1 and R-3, L-1 and L-3 are compressed to 1/4, and R-2 and Compress L-2 to 1/2. R-1, R-3, L-1, and L-3 are A / D converters 201R and 2R, respectively.
A frequency f of 1/4 of the read clock of 4fc at 01L
AD conversion is performed with the clock of c. The digital signal is written in the memories 202R and 202L with the same fc clock as in A / D conversion. At this time, the memories 202R and 202L are driven by the write enable pulse WE2 shown in FIG.
Specify the timing to write to.

Similarly, R-2 and L-2 are A /
The D converters 27R and 27L perform A / D conversion with a clock having a frequency of 2fc, which is a half of the read clock, and the memory 28
The R and 28L are written with the same 2fc clock as the A / D conversion. At this time, the write enable pulse uses WE1 to specify the timing.

Next, among the written digital signals, R-1 and R-3 are timed by the output enable pulse OE2 of FIG. 2 (f), and R-2 is timed by OE1. Are output to the same signal line and are D / A converted by the D / A converter 29R. The analog output signal is the signal of FIG. 2 (e), and as a result, R-1 and R-3 of FIG. 2 (c) are R compressed to 1/4.
-1 ', R-3', R-2 becomes R-2 'compressed to 1/2, and the whole becomes a signal temporally moved to the first half of one horizontal scanning period.

Similarly for L, L-1, L-3
Is the output enable pulse OE4 of FIG.
Further, L-2 is OE3, which is output on the same signal line at each time designated in time, and is D / A converted by the D / A converter 29L. Then, L- in FIG.
The signals 1 ', L-3', and L-2 'become the signals that are temporally moved to the latter half of one horizontal scanning period. The above two signals and the reference pulse P as shown in FIG. 2E generated from the reference pulse generation circuit included in the control unit 20 are added to the adder 2
4 is added to create a signal as shown in FIG. Add the synchronization signal separated in the first stage to this signal by the adder 25,
The signal of FIG. 2 (h) is created and recorded as a recording video signal on the recording medium by the recording / reproducing apparatus of FIG.

Clocks fc, 2fc and 4 used here
fc is a clock that is phase-synchronized with the sync signal by the PLL circuit included in the control unit 20 from the sync signal that has been synchronously separated, and also enable pulses WE1, WE2, and OE1 to OE4 for writing and reading of each memory. It is a pulse generated by counting from the clock by the PLL circuit using the separated horizontal synchronizing signal as a reference for counting.

Next, the separation circuit 4 used during reproduction will be described. FIG. 3 shows an embodiment of the separation circuit 4 as a signal expansion device according to the present invention. The separation circuit 4 is provided in the time axis expansion units 44R and 44L in the circuit of FIG.
/ D converters 401R and 401L and memories 402R and 4
02L is added, a control unit 40 is provided, and a separation unit 403 is provided instead of the synchronization separation circuit 41 of FIG. The separating unit 403 separates the sync signal and the reference pulse P from the reproduced video signal and sends them to the control unit 40.

The control unit 40, based on the separated synchronizing signal and the reference pulse P, writes enable pulses WE11 to WE14 and output enable pulses OE11, OE12 and fc, 2f as shown in FIGS.
c, 4fc clocks and time-axis expansion units 44R, 4R
It controls 4L.

Next, the operation at the time of reproduction with the above configuration will be described. The signal of FIG. 4 (a) reproduced from the recording medium in the recording / reproducing apparatus 3 of FIG. 5 is applied to the separation circuit 4 of FIG. 3, and the separation signal is separated by the separation unit 4 and then added. 2B after being removed from the synchronizing signal by the device 42.
Signal and is added to the time axis extending units 44R and 44L.

In the time axis expansion units 44R and 44L, as shown in FIG.
The signal of (b) is applied to the left and right end portions R-1 ', R-3', L-.
1 ', L-3' and central portions R-2 ', L-2' are temporally separated to form as shown in FIG.
1'and R-3 ', L-1' and L-3 'are expanded 4-fold, and R-2' and L-2 'are expanded 2-fold. For this reason, R-1 'and R-3' and L-1 'and L-3' are A / D converted by the A / D converters 401R and 401L at a clock of 4fc which is four times the read clock. Same as A / D conversion of digital signal to memories 402R and 402L 4f
Write at the clock of c. At that time, R-1 ', R-3'
Is driven by the write enable pulse WE12 and L-
1'and L-3 'designate the timing of writing to the memory by the write enable pulse WE14.

Further, R-2 'and L-2' are A / D converted by the A / D converters 46R and 46L with a clock of 2fc which is twice the read clock, and then stored in the memories 47R and 47L with the same 2fc. Written on the clock. At this time R-
2'uses the write enable pulse WE11 and L-
2'designates the write timing using WE13.

Next, from each memory, R-1 ', R-3',
Output enable pulse O for L-1 'and L-3'
At E12, R-2 'and L-2' are read at the timing designated by the output enable pulse OE11, and the signals shown in FIG. This signal is R- in (b).
1 ', R-3' and L-1 ', L-3 become R-1, R-3, L-1, L-3 which are expanded four times, and R-2', L
-2 'is doubled to R-2 and L-2.

The R-1, R-2, and R-3 are output on the same line, and the L-1, L-2, and L-3 are output on the same line to output D / A converters 48R and 48L. By performing D / A conversion with, the original left and right analog signals as at the time of recording are obtained as shown in FIG. The left and right signals are separated by the separation unit 403.
By inserting the synchronizing signals separated in step 1 by the adders 45R and 45L, the signals shown in FIG. 4H are sent to the right-eye and left-eye display devices 51R and 51L in FIG. 5, respectively.

Clocks fc, 2fc, 4 used here
fc is P in the control unit 40 based on the synchronization signal separated by synchronization.
It is a clock that is phase-synchronized with the synchronizing signal by the LL circuit, and enable pulses for writing and reading of each memory are generated by WE11 and WE12 counting the clock from the PLL circuit with the separated horizontal synchronizing signal as a reference. , WE13, WE14 count and generate clocks with reference to the extracted reference pulse P.
The OE11 and OE12 also generate clocks by counting the clocks with the separated horizontal synchronizing signal as a reference.

In this embodiment, 1/8 of both ends of each of the left and right signal components are compressed to a compression ratio of 1/4, and the center 3
/ 4 is compressed to a compression ratio of 1/2, the right-eye signal is aligned with the leading edge, the left-eye signal is aligned with the trailing edge, and they are added, and a reference pulse is inserted between them to write the recording signal. I made it, but if the effective period of the signal is 53.26 μsec,
The sum of the reference pulse and the time before and after it is approximately 6.66 μs.
ec, and there is almost no effect of jitter during recording / reproduction when extracting the reference pulse. Therefore, writing to the memory during reproduction, especially the latter half of the signal, is performed well, and the reproduced image due to jitter is reproduced. Disturbance does not occur. In addition, since the human eyes cannot clearly recognize that the both ends of the screen are 1/8, the deterioration of the image is not noticeable even if the image is compressed and expanded to 1/4.

In this embodiment, the reference pulse is about 6.
It is set to 66 μsec and the compression rate is set to 1 because of the ease of making the clock.
However, if the reference pulse is set to 5 μsec or more and the clocks at the time of recording and reproduction can be accurately matched, the compression rate can be set arbitrarily within the range that does not deteriorate the central image. You may choose.

According to the present embodiment, two video signals are time-compressed within one horizontal scanning period to obtain one video signal.
When recording and reproducing with a VTR, etc. by making a system video signal,
Each of the two signals is compressed with a low compression rate at the center of the display screen and a high compression rate at both ends, and one of the compressed signals is temporally aligned with the leading edge of the effective range of the video signal. Move it, move the other one to the trailing edge,
Secure an interval of 5 μsec or more between the two signals,
By inserting a reference pulse as a reference of the time axis of the signal aligned with the trailing edge during reproduction and recording / reproducing as a single-system video signal, a part of the video signal is not lost, and compression / expansion is performed. It is possible to suppress deterioration of image quality in the central portion of the screen. In addition, the reference pulse can be extracted from the reproduced signal without being affected by jitter, and during recording, the signal that matches the trailing edge of the effective range of the video signal can be satisfactorily written to the memory and the image due to jitter It has the effect of absorbing the disturbance.

[0039]

As described above, according to the first aspect of the present invention, it is possible to prevent a part of a signal from being lost by appropriately selecting and compressing the compression ratio of each signal of a plurality of signals. can do. According to the second aspect of the present invention, it is possible to prevent a part of the displayed image from being lost by appropriately selecting the compression rate according to the position of one horizontal scanning period and compressing the two video signals. You can

According to the invention of claim 3, by lowering the compression rate of the video signal in the vicinity of the center of one horizontal scanning period and increasing the compression rate of the video signal in the vicinity of both ends, deterioration of the image in the vicinity of the center of the screen. Can be minimized.
According to the invention of claim 4, of the two compressed signals which are arranged one after another in time, one signal is arranged at a position aligned with the leading edge portion of the effective image position during one horizontal scanning period. The reference signal can be inserted by arranging the other by temporally moving it to a position that matches the trailing edge portion and forming one signal.

According to the invention of claim 5, the reference signal can be extracted without affecting the signal component at the time of decompression by setting the time for inserting the reference signal to a predetermined time or more, and the image deterioration due to the jitter can be achieved. Can be suppressed. According to the invention of claim 6, in the remaining period excluding the time for inserting the reference signal, the compression rate near the center of one horizontal scanning period is decreased and the compression rate near both ends is increased,
By arranging the two compressed signals before and after the reference signal, the deterioration of the image near the center of the screen is minimized without losing a part of the video signal, and the reference signal is used as a signal component during reproduction. Can be extracted without affecting the image quality, and image deterioration due to jitter can be suppressed.

According to the invention of claim 7, the signals of the respective compressed parts are expanded at an expansion ratio according to the respective compression ratios, and the expanded signals of the respective parts are rearranged and output as the plurality of signals. By doing so, it is possible to prevent a part of the plurality of output signals from being lost. According to the invention of claim 8, the two compressed signals are expanded at an expansion ratio according to the compression ratio, and the two expanded signals are respectively output as two video signals in one horizontal scanning period. Thus, it is possible to prevent a part of the two output video signals from being lost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a signal compression apparatus according to an embodiment of the present invention.

FIG. 2 is a timing chart showing a signal compression operation.

FIG. 3 is a block diagram showing a signal decompression device according to an embodiment of the present invention.

FIG. 4 is a timing chart showing a signal expansion operation.

FIG. 5 is a block diagram showing a conventional image recording / reproducing apparatus to which the present invention is applied.

FIG. 6 is a timing chart showing a conventional signal compression operation.

FIG. 7 is a block diagram showing a conventional mixing circuit for performing signal compression.

FIG. 8 is a timing chart showing a conventional signal expansion operation.

FIG. 9 is a block diagram showing a conventional separation circuit that performs signal expansion.

FIG. 10 is a timing chart showing a case where a reference pulse is inserted between two conventional compressed signals.

[Explanation of symbols]

 23R, 23L time base compression unit 20 control unit 24 adder 44R, 44L time base expansion unit 40 control unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04N 7/30 H04N 7/133 Z

Claims (8)

[Claims] 1. A plurality of signals are each divided into one or more parts, the signals of each part are compressed at a predetermined compression rate, and the compressed signals of each part are arranged in a predetermined order to obtain 1
A signal compression device characterized by outputting as one signal. 2. A compression means for compressing the two video signals by changing the compression rate according to their positions within one horizontal scanning period, and the two compressed video signals before and after within one horizontal scanning period. A signal compression device, comprising: an output unit that is arranged and outputs as one video signal. 3. The signal compression apparatus according to claim 2, wherein the compression ratio of the video signal near the center within the one horizontal scanning period is lowered and the compression ratio of the video signal near both ends is increased. 4. One of the two compressed video signals is arranged at a position aligned with the leading edge portion of the effective image position during one horizontal scanning period, and the other signal is aligned with the trailing edge portion. 3. The signal compression device according to claim 2, wherein the signal compression device is arranged so as to be moved to a position in time, and a reference signal is inserted between these two signals to form one signal. 5. The signal compression apparatus according to claim 4, wherein a time for inserting the reference signal is secured for a predetermined time or more. 6. The two compressed signals are arranged before and after the remaining period excluding the time for inserting the reference signal, and the compression ratio of the signal to the vicinity of the center within the one horizontal scanning period is set. 5. The signal compression device according to claim 4, wherein the signal compression ratio is set low and the signal compression ratio in the vicinity of both ends is increased. 7. A signal formed by dividing a plurality of signals into one or more parts, compressing the signals of the parts at a predetermined compression ratio, and arranging the compressed signals of the parts in a predetermined order. The signal of each of the compressed parts is expanded at an expansion rate according to the compression rate, and the signals of the expanded parts are rearranged and output as the plurality of signals. A characteristic signal expansion device. 8. The two video signals are respectively compressed within one horizontal scanning period at different compression rates according to their positions, and the two compressed signals are arranged before and after one horizontal scanning period. Image signals are input, the two compressed signals are expanded at an expansion rate according to the compression rate, and the two expanded video signals are respectively expanded by 1
A signal decompressor adapted to output during a horizontal scanning period.