JP2603290B2 - Color video signal processing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color video signal processing method, and more particularly to a color video signal processing method for performing high-efficiency encoding.

[Related Art] Generally, in a color video signal including a luminance signal and two kinds of color difference signals, the band of the color difference signal is narrower than the band of the luminance signal, and the sampling frequency at the time of digitization is also the luminance signal. Will be set to about 1/4 of the sampling frequency of

Further, considering the visual characteristics on the screen, even if the information amount of the chrominance signal is further compressed with respect to the information amount of the luminance signal, it is inconspicuous. However, simply lowering the sampling frequency of the chrominance signal further results in a noticeable decrease in the resolution in the horizontal direction.

Therefore, two types of color difference signals (C _N , C _W ) are line-sequentially reduced to 1/2 the amount of information, or an offset sub-pixel that transmits pixels shifted between lines or between fields and thins out other pixels. It has been proposed to reduce the information amount by half by sampling.

On the other hand, in recent years, video signals have become higher definition and the number of scanning lines has been reduced.
Testing of more than 1000 so-called high definition television signals has also been performed. Therefore, the amount of information of a video signal tends to further increase, and in consideration of the limit of the transmission speed of a transmission line, the amount of information must be further compressed, and various high-efficiency coding methods have been proposed.

As one example of this high efficiency coding method, one screen is represented by (n
There is a block coding that divides the data into coding blocks consisting of (xm) sample points and compresses information without deteriorating the image quality by using the correlation of each pixel in each block. This block coding is advantageous in that the coding can be performed using the pixels having the highest correlation, so that the deterioration of the image quality is small and the propagation of code errors is suppressed only within each block.

[Problems to be Solved by the Invention] Accordingly, in the present invention, when a component video signal composed of two types of color difference signals and a luminance signal is transmitted or recorded / reproduced, block coding is efficiently performed on the two types of color difference signals. To provide a new color video signal processing method capable of performing the following.

[Means for Solving the Problems] Under such a purpose, according to the color video signal processing method of the present invention, the digital luminance signal and the line-sequential 2
Digital chrominance signals are input, and the input digital luminance signal is encoded for each block of (n × m) samples (n and m are each an integer of 2 or more). Encoding for each block of (n × m) samples straddling a line on which different color difference signals are arranged,
The encoded digital luminance signal and digital chrominance signal are time-division multiplexed and transmitted.

[Operation] With the above-described configuration, it is possible to encode a luminance signal and a color difference signal with an extremely high compression rate and without significant image quality deterioration.

Further, since the encoded luminance signal and color difference signal are transmitted in a time-division multiplexed manner, it is possible to easily manage the transmission path.

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a diagram showing a schematic configuration of a color video signal transmission system as one embodiment of the method of the present invention. In the figure, 2 is an input terminal of a luminance signal (Y), and 4 and 6 are color difference signals (C
_N , C _W ) input terminals. The input luminance signal is sampled by the A / D converter 8 and input to the block forming circuit 10.
The block forming circuit 10 is a circuit for reading a digital luminance signal in a raster scanning order for each block of (4 × 4) pixels.

FIG. 2 is a diagram for explaining the operation of the blocking circuit. In the drawing, solid lines indicate scanning lines of the first field, broken lines indicate scanning lines of the second field, and dashed lines indicate boundaries of the blocks. That is, the block forming circuit 10 uses the pixel numbers shown in circles to indicate 1 → 2 → 3 → 4 → 17 → 18 → 19 → 20 → ... → 9 → 10 → 11 →
Data entered in the order of 12 → 25 → 26 → 27 → 28 →… is 1 →
Output in the order of 2 → 3 → 4 → 5 → 6 → 7 → 8 → 9 →.

The encoding circuit 12 performs block encoding on the data read from the block encoding circuit 10 to reduce the amount of information (the number of bits per pixel) and then outputs the data.

On the other hand, the color difference signals C _N and C _W input from the input terminals 4 and 6 are converted into digital signals by the A / D converters 14 and 16 by a sampling clock having a frequency 1/4 of the luminance signal. The digitized color difference signals C _N and C _W are supplied to the pre-filters 15 and 17 at the next stage, and the frequency in the vertical direction is limited. The color difference signals C _N and C _W output from the pre-filters 15 and 17 are line-sequentialized by the switch 21 in accordance with the rectangular wave inverted from the switching control circuit 19 every horizontal scanning period. FIG. 3 shows the arrangement of the color difference signals C _N and C _W on the screen in the line-sequentialized signal. In the figure, the solid line indicates the first field and the broken line indicates the second field, and C _N and C _W are arranged in units of two lines in each frame as shown in the figure.

The line-sequentialized color difference signals C _N and C _W are supplied to a block forming circuit 23, where they are rearranged for each block and supplied to an encoding circuit 25 as in the case of the block forming circuit. In the encoding circuit 25, the pixel interval in the horizontal direction is different from that in the case of the luminance signal, but the encoding is performed using the correlation in the encoding block of (4 × 4) pixels. At this time, when the block shown in FIG. 2 is taken, if each pixel on the line including pixels 1 and 5 is _CW , then each pixel on the line including pixels 9 and 13 is C _N
Becomes

The line-sequential chrominance signal block-encoded by the encoding circuit 25 is time-multiplexed by the multiplexing circuit 30 with the block-encoded luminance signal, and is transmitted to a transmission line 34 such as a communication device or a magnetic recording / reproducing device via a terminal 32. Sent out.

FIG. 4 shows an example of the configuration of the pre-filter in the above system. In the figure, 101 is an input terminal, 102 and 103 are one horizontal scanning period (1H) delay circuits, 104, 105, and 107 are 1/2 coefficient units, 106 is an adder, and 108 is an output terminal. This pre-filter limits the maximum frequency in the vertical direction to about 1/2.

Examples of the block coding method include orthogonal transform coding, vector quantization, and coding for transmitting a quantization index obtained by linearly quantizing the maximum and minimum values in a block and between each pixel. , A coding method using the correlation in the block can be applied.

According to the configuration as described above, since the color difference signals that have been line-sequentialized are block-coded, it is possible to compress information at a high compression rate. It is generally known that there is a high correlation between the two types of color difference signals C _N and C _W , and high-efficiency encoding is possible by suppressing the size of the encoding block to a small value. Further, if one encoding block can be reproduced, both of the two types of color difference signals C _N and C _W can be restored. Therefore, when this encoding process is applied to a digital VTR,
Since color restoration is possible even when a so-called high-speed search is performed, it can be said that the processing is very suitable for such a digital VTR.

 Next, the decoding system will be described.

The color video signal via the transmission path 34 is supplied to a separation circuit 38 via a terminal 36, and is separated into a luminance signal and a line-sequential color difference signal. These are supplied to block decoding circuits 40 and 43, respectively, and are decoded by the reverse processing of the coding circuits 12 and 25 to restore the information amount. The decoded luminance signal and line-sequential chrominance signal are array-converted from a block order to a scanning line order by a rasterization circuit.

The rasterized line-sequential color difference signal is supplied to the B input of the switch 53 and the A input of the switch 55. Switching-control circuit 50 supplies a rectangular wave is inverted every 1 horizontal scanning period to switch 53 and 55, the C _N line-sequential color difference signal outputted from the rasterizer 49 to the interpolation filter 57, interpolation and C _W filter Supplied to 59. At this time, all corresponding to the zero level in the horizontal scanning period in which no C _N is the interpolation filter 57 "0"
Are supplied to the interpolation filter 59, and all "0" data corresponding to the 0 level is supplied to the interpolation filter 59 in the horizontal scanning period in which _CW does not exist.

The structure of the interpolation filters 57 and 59 is the same as that of the filter of FIG. 4, but the data of one line out of two lines is replaced with the data corresponding to the zero level, so that the average level is reduced to half at this point. As a result, the coefficient unit 107 becomes unnecessary. The interpolation filters 57 and 59 convert the line sequential signals into two types of color difference signals C _N and C _W. These are the D / A converters 58 and 6, respectively.
The output of the rasterization circuit 46 is directly supplied to the D / A converter 56 for the luminance signal. At this time, D / A
The operating frequency of the converter 56 is four times that of the D / A converters 58 and 60,
The luminance signals and color difference signals C _N and C _W converted into analog signals by these D / A converters 56, 58 and 60 are output from terminals 62, 64 and 66 as component color video signals.

Although the size of the coding block in the above embodiment has been described as being (4 × 4) pixels, it is generally (n × m).
The same effect can be obtained if the pixel (n ≧ 2, m ≧ 2), and the values of n and m can be arbitrarily determined according to the coding system, data compression rate requirement, and the like.

[Effects of the Invention] As described above, according to the present invention, it is possible to compress information at an extremely high compression rate without deteriorating the image quality of the luminance signal and the color difference signal.

Further, since the encoded luminance signal and color difference signal are transmitted in a time-division multiplexed manner, it is possible to easily manage the transmission path.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a color video signal transmission system as one embodiment of the method of the present invention, FIG. 2 is a diagram for explaining the operation of a block circuit in FIG. 1, FIG. FIG. 4 is a diagram showing an arrangement of each color difference signal on a screen of a line-sequential signal, and FIG. 4 is a diagram showing a configuration of a pre-filter in FIG. In the figure, 4,6 ... color difference signal input terminal 21 ... switch 23 ... blocking circuit 25 ... block coding circuit

Claims (1)

(57) [Claims] 1. A digital luminance signal and two kinds of line-sequential digital color difference signals are inputted, and the inputted digital luminance signal is sampled by (n × m) samples (n and m are each an integer of 2 or more). The input digital chrominance signal is coded for each block of (n × m) samples straddling a line on which different chrominance signals are arranged, and the coded digital luminance signal and the digital chrominance signal are coded. A color video signal processing method, wherein a signal is time-multiplexed and transmitted.