JPH01261096A - Color video signal processing method - Google Patents

Abstract

PURPOSE:To attain compression of information with a high compression rate by applying clock coding to a color difference signal subjected to information compression by subsampling and line sequencing. CONSTITUTION:Digitized color difference signals CN, CW are subjected to line sequencing by a switch 17 in response to a rectangular wave inverted for each one horizontal scanning period from a switching control circuit 19, fed to a 2-line offset subsampling circuit 21 so as to subjected to subsampling in a way that the horizontal position of the output picture element differs from each 2-line. Then the signal is fed to a separation block circuit 23, in which a block processing is obtained from the color difference signals CN, CW and block coding is applied by coding circuits 24, 26. Then the result is subjected to time base multiplex with a coded luminance signal Y by a multiplex circuit 30 and the result is sent to a transmission line 34. Thus, the information is compressed with a high compression rate.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a color video signal processing method.

In particular, the present invention relates to a color video signal processing method that performs high-efficiency encoding.

[Prior Art] Generally, 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 during digitization also differs from that of the luminance signal. The sampling frequency is set to about h.

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 decrease in resolution in the horizontal direction.

Therefore, conventionally two types of color difference signals (C, .

It has been proposed to line-sequentialize Cw) to determine the amount of information, or to determine the amount of information by offset subsampling, which transmits pixels shifted between lines or fields and thins out other pixels.

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 quality (formerly Definition)
Television signals are also being tested. Therefore, the amount of information in video signals 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 encoded blocks each consisting of x 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.

[Problems to be Solved by the Invention] Therefore, the present invention provides efficient block encoding for the two types of color difference signals when transmitting or recording/reproducing a component video signal consisting of two types of color difference signals and a luminance signal. This paper aims to present a novel color video signal processing method that can perform the following steps.

[Means for Solving the Problems] With this objective in mind, in the color video signal processing method of the present invention, line sequentialization and subsampling are performed on two types of digital color difference signals, and subsampler processing is performed. For each of the two types of color difference signals in the line sequential color difference signal, encoding is performed for each block of (n× type) samples (n and m are each an integer of 2 or more).

[Operation] By doing as described above, block encoding is performed on the color difference signals whose information has been significantly compressed by subsampling and line sequentialization, so that the compression rate is extremely high and the optimum encoding is performed for each color difference signal. It became possible to do so.

[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.
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.
CM, CW) input terminal. The input luminance signal is sampled by the A/D converter 8, and then subjected to field offset subsampling (FOSS) in the pre-filter 7.
Limit the band to avoid aliasing noise in the circuit. The luminance signal from the prefilter 7 is sent to the FOSS circuit 9. Sub-ombring will be done at.

FIG. 2 shows the positional relationship between the output pixel and the thinned-out pixel in this FOSS circuit 9. In Fig. 2, the solid line is the scanning line of the first field, and the broken line is the scanning line of the second field.
is a pixel to be transmitted to the subsequent stage, and × is a pixel to be thinned out.

The FOSSed luminance signal is input to the blocking circuit 10. The blocking circuit 10 is a circuit that reads out digital luminance signals in raster scanning order for each block of (4×4) pixels.

FIG. 3 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 the blocks. In other words, the blocking circuit 10 uses the pixel numbers shown within 0 from 1→2→ 3→4→17→18→19→20→・・・→9
→１０→１１→１２→２５→２６→２７→２８→・・・
Data entered in the order of 1 → 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 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,,C input from the input terminal 4.6
, are respectively converted into digital signals by A/D converters 14 and 16 using a sampling clock having a frequency of % of the luminance signal. The digitized color difference signals C, , C, are supplied to the next-stage prefilter 13.15, and are two-dimensionally band-limited in the subsequent line sequential circuit and sub-samples to prevent aliasing interference.

Prefilter 13. Color difference signals C, , output from Is
C, is line-sequentialized by the switch 17 in response to a rectangular wave from the switching control circuit 19 that is inverted every horizontal scanning period. Color difference signal CN on the screen in this line sequential signal.

The arrangement of co is shown in FIG. In the figure, the solid lines indicate the scanning lines of the first field, and the broken lines indicate the scanning lines of the second field, and as shown in the figure, Cs and Cw are arranged in units of two lines in each frame.

The line-sequential color difference signal output from the switch 17 is supplied to a 2-line offset subsampling (2LOSS) circuit 21, where it is sub-sampled so that the horizontal position of the output pixel is different every two lines. FIG. 5 shows the positional relationship between the output pixel and the thinned-out pixel in this 2LOSS circuit 21.

In the circuit 21, as shown in the figure, the output pixels are offset every four lines for the scanning lines in one frame, or if only the same color difference signal of each field is considered, the output pixels are offset every line.

The output of the 2LOSS circuit 21 is supplied to a separation block forming circuit 23, which blocks each of the color difference signals C, , C, and obtains two systems of blocked signals. FIG. 6 is a diagram for explaining the operation of this separation block forming circuit. That is, the circuit 23 is connected from the 2LOSS circuit 21 to O in the figure.
The pixel numbers shown inside are l → 2 → 3 → 4 → 33 → 34 → 35.
→３６・・・・・・→１７→１８→１９→２０→・・・
...→9→10→11→12→... The signals output in the order of 17→18→19→20→21→22→23
→24→25→26→27→28→... is supplied to the encoding circuit 24 in the order of 1→2→3→4→5→6→7→8→
9... are supplied to the encoding circuit 26 in this order.

The color difference signals C, , C, block encoded by the encoding circuits 24 and 26 are time-axis multiplexed with the block encoded luminance signal by the multiplexing circuit 30 and sent to the communication device r1 via the terminal 32.
The signal is sent to a transmission path 34 of a one-time recording/reproducing machine or the like.

Note that block encoding methods include, for example, orthogonal transform encoding, vector quantization, and encoding that transmits quantization indexes obtained by linearly quantizing the maximum and minimum values within a block and the spaces 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. Furthermore, by using the encoding circuits 24 and 26 to perform encoding suitable for each of CH and 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, where it is divided into a luminance signal and a color difference signal CN.
, Cw. These are supplied to block decoding circuits 40, 42 and 44, respectively, and encoded circuits 12 and 26.
It is decoded by the reverse process of ゜28, and the amount of information is restored to its original value.

The decoded luminance signal is array-converted in a rasterization circuit 46 from block order to scanning line order.

The rasterized luminance signal is supplied to the x side terminal of the switch 52. The switching control circuit 50 supplies the switch 52 with a rectangular wave signal that is inverted every sampling period of the A/D converter 8, and the switch 52 alternately switches rasterized luminance signal data and data corresponding to 0 level. and input to the interpolation filter 55. The interpolation filter 55 interpolates thinned out pixels using one-dimensional or two-dimensional correlation.

On the other hand, the decoded color difference signals CM and Cw are supplied to a multiplex rasterization circuit 49, where they are array-converted into line-sequential color difference signals in the reverse procedure of the separation and block formation circuit 23.

The rasterized line-sequential color difference signal is supplied to the B input of the switch 53 and the eight inputs of the switch 55. The switching control circuit 50 supplies a rectangular wave that is inverted every sampling period of the A/D converters 14 and 16 to the switches 53 and 55 every horizontal scanning period, and outputs the line-sequential color difference signal from the multiple rasterization circuit 49. C, to the interpolation filter 57,
co is supplied to the interpolation filter 59.

At this time, the interpolation filter 57 is supplied with all zero data corresponding to the 0 level during the sample period and horizontal scanning period in which 0.4 does not exist, and the interpolation filter 59 is supplied with
All "0" data corresponding to the 0 level is supplied during the sample period and the horizontal scanning period when the "8" does not exist.

The interpolation filters 57 and 59 interpolate the thinned out pixels and the thinned out horizontal scanning lines in the vertical and horizontal directions and output them as two types of color difference signals c, , Cw.

In this way, the rasterized luminance signal and color difference signal C
n and Cw are supplied to D/A converters 56, 58, and 60 via interpolation filters 5.5 and 57.59, respectively. At this time, the orbital frequency of the D/A converter 56 is four times that of the D/A converter 58.60, and these D/A converters
luminance signals converted into analogs by converters 56, 58, and 60;
The color difference signals C, 1, and Cw are outputted from terminals 62°64.66 as component color video signals.

In the above embodiment, the luminance signal and color difference signal are subsampled by field offset subsampling and two line offset subsampling, but the subsampling pattern is not limited to this. It is also possible to use different sampling patterns for each color difference signal.

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

[Effects of the Invention] As described above, according to the present invention, there is provided a color video signal processing method capable of compressing information at an extremely high compression rate 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, and FIG. 2 is a diagram showing the positional relationship between output pixels and thinned-out pixels by a luminance signal field offset subsampling circuit. 3 is a diagram for explaining the operation of the luminance signal blocking circuit in FIG. 1, FIG. 4 is a diagram for explaining line sequentialization of color difference signals in the system in FIG. 1, Figure 5 is a diagram showing the positional relationship between output pixels and thinned-out pixels by the 2-line offset subsampling circuit for color difference signals, and Figure 6 explains the operation of the blocking circuit for color difference signals in the system in Figure 1. This is a diagram for In the figure 4, 6...Color difference signal input terminal 17...Switch 21...2 line offset sub-sampling circuit 23...Separation block forming circuit 24.28...Block encoding circuit

Claims (1)

[Claims] Line-sequentialization and subsampling are performed on two types of digital color difference signals, and each of the two types of color difference signals in the subsampled line-sequential color difference signals (n×m) is
A color video signal processing method that encodes each block of samples (n and m are integers of 2 or more).