JPH01260986A - Color video signal processing method - Google Patents

Abstract

PURPOSE:To attain information compression with a high compression rate by applying sub-sampling to each of 2 kinds of digital color difference signals and applying coding for each block of (nXm) sample (n, m are integers being 2 or over) as to 2 kinds of color difference signals subjected to sub sampling. CONSTITUTION:In the operation of a block processing circuit, solid lines in figure represent the scanning line of a 1st field and broken lines illustrate the scanning line of a 2nd field and an alternative long and short dash line indicate borders of blocks. That is, the block processing circuit 10 outputs data in the order of picture element numbers written in rounds 1 2 3 4 5 6 7 8 9... inputted in the order of 1 2 3 4 17 18 19 20... 9 10 11 12 25 26 27 28 .... A color difference signal subjected to block coding by coding circuits 26, 28 is subjected to time base multiplex with a luminance signal subjected block coding by a multiplex circuit 30 and sent to a transmission line 34 for a communication equipment or a magnetic recording and reproducing device via a terminal 32.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color video signal processing method, and more particularly to a color video signal processing method that performs high efficiency encoding.

[Conventional technology]

In general, in a color video signal consisting of a luminance signal and two types of color difference signals, the band of the color difference signal is narrower than that of the luminance signal, and the sampling frequency when digitizing is also different from that of the luminance signal. It will be set to about 1/4 of the frequency.

Furthermore, considering the visual characteristics on the screen, it is not noticeable even if the amount of information of the color signal is further compressed compared to the amount of information of the luminance signal. However, simply lowering the sampling frequency of the color difference signal further will result in a noticeable drop in resolution in the horizontal method.

Therefore, conventionally, two types of color difference signals (CN, CW) are line-sequentialized to reduce the amount of information to half, or pixels shifted between lines or fields are transmitted and thinned out to other pixels (
It has been proposed to reduce the amount of information to 1/2 by offset subsampling.

On the other hand, in recent years video signals have become even more high-definition, with the number of scanning lines increasing to 1.
,000 or more so-called high-definition (Hi Definit)
ion) Television signals are also being tested. Therefore, the amount of information in a video signal tends to further increase, and when the limit of the transmission speed of the transmission path is taken into account, the amount of information must be further compressed, and various high-efficiency encoding methods have been proposed.

As an example of this high-efficiency encoding method, one screen is (n
There is block encoding in which information is divided into encoding blocks each consisting of ×m) sample points and the correlation between each pixel in each block is used to compress information without deteriorating image quality. This block encoding is advantageous in that the deterioration in image quality is small because encoding can be performed using pixels with the highest correlation, and the propagation of code errors is suppressed only within each block.

[Problem that the invention seeks to solve]

Therefore, when transmitting or recording/reproducing a component video signal consisting of two types of color difference signals and a luminance signal, the present invention proposes a novel color video signal processing method that can perform block encoding for the two types of color difference signals. The purpose of this paper is to present a method.

[Means for solving problems]

For this purpose, in the color video signal processing method of the present invention, subsampling is performed for each of the two types of digital color difference signals, and for each of the two types of subsampled color difference signals (n×m )sample(
Encoding is performed for each block (n and m are integers of 2 or more).

[Effect]

By doing as described above, the color difference signals whose information has been compressed by subsampling are subjected to block coding, so that the compression rate is extremely high and it is possible to perform optimal coding for each color difference signal.

〔Example〕

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 an embodiment of the method of the present invention. 2 in the diagram
4.6 is the input terminal for the luminance signal (Y), and 4.6 is the input terminal for the color difference signal (Y), respectively.
CN+Cw) input terminal. The input luminance signal is sampled by the A/D converter 8 and then sent to the blocking circuit 10.
is input. The blocking circuit 10 is a circuit that reads out digital luminance signals in raster scanning order for each block of (4×4) pixels.

Figure 2 is a diagram for explaining the operation of the blocking circuit.
In the figure, the solid lines indicate the scanning lines of the first field, the broken lines indicate the scanning lines of the second field, and the dashed-dotted lines indicate the boundaries of blocks. In other words, the blocking circuit 1o has the pixel numbers shown in circles: 1→2→3→4→17→18→19→20→...→9
→１０→１１→１２→２５→２６→２７→２８→・・・
The data input in the order of l → 2 → 3 → 4 → 5 → 6 → 7
Output in the order of →8→9→...

The encoding circuit 12 performs block encoding on the data read out from the blocking circuit 1o to reduce the amount of information (the number of bits per pixel) and then outputs the data.

On the other hand, color difference signals CN are input from input terminals 4 and 6.

Cw is 1/4 of the luminance signal at the A/D converter 14 and 16, respectively.
is converted to a digital signal using a sampling clock with a frequency of The digitized color difference signals CN and CW are sent to the next stage field offset subsampling circuit (FO3S).
) Subsampled at 18.20.

This FO3S18. FIG. 3 shows the positional relationship between the output pixel and the thinned-out pixel in No. 20. In FIG. 3, the solid lines are the scanning lines of the first field, the broken lines are the scanning lines of the second field, O indicates the pixel to be transmitted to the subsequent stage, and x indicates the thinned-out pixel. Of course, the interval between each pixel is four times the luminance signal.

The sub-sampled color difference signals CN and CW are respectively sent to the blocking circuit 22 in raster scanning order. Supplied to 24,
As in the case of the blocking circuit 10, the arrangement is converted for each block and the encoding circuit 26. 28.

The color difference signals CN and CW block-coded by the coding circuits 26 and 28 are time-axis multiplexed with the block-coded luminance signal by the multiplexing circuit 30, and sent to a communication device, magnetic recording/reproducing device, etc. via a terminal 32. The signal is sent to the transmission path 34.

In addition, the color difference signals CN and CW in FO3S18 and 20
Even if each transmission pixel is the same as shown in FIG. 4(a),
They may be different as shown in Figure (b). In Fig. 4, ○ indicates a CN transmission pixel, △ indicates a CW• transmission pixel, and × indicates a CN transmission pixel.

Cw also indicates pixels to be thinned out. In addition, block encoding methods include, for example, orthogonal transform encoding, vector quantization, and encoding that transmits a quantization index obtained by linearly quantizing the maximum and minimum values within a block and the values between them for each pixel. , an encoding method using intra-block correlation can be applied.

According to the configuration described above, since the subsampled color difference signal is block encoded, information compression with a high compression rate is possible, and since only pixels of the same type exist in each encoded block, highly efficient band compression is possible. is possible. Further, an encoding circuit 26. CN 28.

By performing encoding suitable for each Cw, even more efficient compression can be achieved.

Next, the decoding system will be explained.

The color video signal via the transmission line 34 is supplied to a separation circuit 38 via a terminal 36, and is divided into a luminance signal and a color difference signal CN.
, CW. These are supplied to block decoding circuits 40, 42, 44, respectively, and encoding circuits 12, 26 .
The data is decoded by the reverse process of 28, and the amount of information is restored to its original value. Decoded luminance signal and color difference signal CN.

Each Cw is array-converted from block order to scanning line order by a rasterization circuit.

The rasterized color difference signals CN and CW are sent to the interpolation circuit 52.
After interpolating the thinned out pixels in 54, the D/A converter 5
8.60, and as for the luminance signal, the output of the rasterization circuit 46 is directly supplied to the D/A converter 56. At this time, the operating frequency of the D/A converter 56 is four times that of the D/A converter 58.60, and these D/A converters 56
, 58.60, luminance signal and color difference signal C
N and CW are terminals 62.N and CW as component color video signals. Output from 64.66.

In the above embodiment, the subsampling is field offset subsampling, but the subsampling pattern is not limited to this. It is also possible to use different sampling patterns for each signal.

Also, the size of the encoded block in the above embodiment is (
Although we have explained the case of 4×4) pixels, in general, the same effect can be obtained with (n×m) pixels (n≧2.m≧2), and the values of n and m are the data compression rate of the encoding method. This can be determined arbitrarily based on the requirements of the public.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a color video signal processing method capable of compressing information at an extremely high compression ratio without deteriorating the image quality of color difference signals.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a color video signal transmission system as an embodiment of the method of the present invention, FIG. 2 is a diagram for explaining the operation of the blocking circuit in FIG. 1, and FIG. 4A and 4B are diagrams showing the positional relationship between output pixels and thinned-out pixels by the field offset subsampling circuit, respectively. FIGS. In the figure, 4.6・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・Color difference signal input terminals 18, 20・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・Field offset subsampling circuit

Claims (1)

[Claims] Subsampling is performed for each of the two types of digital color difference signals, and encoding is performed for each block of (n×m) samples (n and m are integers of 2 or more) for each of the two types of subsampled color difference signals. Color video signal processing method.