JPS63222581A - Method and device for color picture transmission processing - Google Patents

Abstract

PURPOSE:To simplify hardware by specifying the proportion of the number of luminance signal picture elements for constituting a color picture to the number of color signal picture elements, and the proportion of color signal levels to the number of luminance signal levels also, then transmitting the data. CONSTITUTION:The proportion of color signal picture elements to the number of luminance signal picture elements to constitute a color image is processed to be 1/8 in vertical direction and 1/16 in horizontal direction, plus, the proportion of color signal level number to the luminance signal level number is processed to be 1/4 vertically and 1/6 horizontally, then the data are transmitted. In an A/D conversion part 2, an A/D converter is selected so that color difference signals I,Q comes to be 1/4 through 1/6 of luminance signal Y in terms of level number, while in a sub-sampling part 10, the proportion in terms of the number of picture elements of the signals I, Q to the signal Y is made 1/8 vertically and 1/16 horizontally. Therefore, the number of picture elements to be processed can be made less than the conventional case, hence the hardware of a coding part 14 can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for transmitting color images using a transmission path with a narrow transmission band.

(Prior Art) As an example of this kind of conventional technology, there is the following publication, for example, "Confucianism Branch Axis."

IT85-61, (1985) 12. IEICE, Murakami, High Efficiency Image Coding by Vector Quantization, pp. 1-8. There is something shown in ``. FIG. 2a is a block diagram of one example of the conventional color image transmission method. The processing flow of the example block diagram shown in FIG. 2a will be described below. A color image signal (NTSC signal) is generally separated into a luminance signal Y and a color signal I by a color signal separation circuit l.
, Q, and each is converted from an analog signal to a digital signal. The converted digital signal is multiplexed into a TDM signal consisting of a color signal and a luminance signal in a TDM conversion circuit 3, and then passed to an encoding circuit 4, where it is subjected to inter-frame/intra-frame composite differential encoding. Encoding processes such as vector quantization and vector quantization are performed.

The encoded signal is converted into a transmission format by the transmission control circuit 5 and sent to the transmission path 50.

From the signal that has passed through the transmission path 50, only the image signal is extracted by the transmission control circuit 5 on the receiving side.

Next, it is converted into TDM format by the decoding circuit 6. Then, the TDM inverse conversion circuit 7 separates the analog signal into a luminance signal and a chrominance signal. Next, it becomes an analog signal in the conversion section 8, and finally it is converted into an NTSC signal by the NTSC synthesis circuit 9.
This becomes a multiplex signal of SC.

Further, as other examples of this type of conventional technology, there are the following publications, such as "Confucian Branch Axis, IE83-101.

(1983), Institute of Electronics and Communication Engineers, Yamaguchi, Component Codes of Color Images, pp. 1-8. This other example is different from the one example shown in Figure 2a,
The luminance signal Y and the color signal I can be converted without providing the TDM conversion circuit 3.
, Q, but the details are omitted.

(Problems to be Solved by the Invention) However, one example of the conventional technology has the following drawbacks.

Table 1 above shows the ratio of the luminance signal to the color difference signal in each conventional encoding system.

The ratio of the number of pixels of the luminance signal and the color signal and the number of gradations for configuring the screen in the conventional method are as shown in Table 1. As can be seen in the first table, the ratio of the number of pixels of the luminance signal and the color signal in the horizontal direction is 6: 1. The ratio is about 2:1 in the vertical direction.

The number of gradations is 8 bits (256) for both the luminance signal and the color signal. In order to transmit such a large number of pixels, complex encoding circuits such as vector quantization and interframe composite difference are required. This has the disadvantage that the hardware scale of the encoding and decoding sections becomes large.

Next, Table 2 shows the number of pixels for the screen configuration in the encoding system shown as another example of the prior art.

In this method, the pixel number ratio between the luminance signal and the color signal is 2=1 in the horizontal direction and 1=1 in the vertical direction. death.

The absolute value of the color signal pixel count is 128×120, which requires a considerable amount of information. In order to transmit this information using a narrowband transmission path, a complicated algorithm (brightness/chrominance difference vector quantization) is required, and the hardware scale becomes large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color image transmission processing method and apparatus which eliminates the above-mentioned drawbacks and solves the problems of hardware scale and economy.

(Means for Solving the Problems) The present invention specifies the ratio of the number of color signal pixels to the number of luminance signal pixels in both the vertical and horizontal directions for configuring a color image when a small screen is assumed. A similar method and apparatus are constructed as follows even when preprocessing is performed to specify the ratio of the number of color signal gradations to the number of luminance signal gradations, and the method and apparatus are used for encoding, transmitting, and decoding. In other words, in a method in which a color image signal is separated into a luminance signal and a color signal and transmitted using a small screen (1.5 to 5 inches), the number of color signal pixels relative to the number of luminance signal pixels to configure a color image is The ratio is 1/1 from IA in both the vertical and horizontal directions.
6, and the ratio of the number of color signal gradations to the number of luminance signal gradations is reduced from 1/4 to 1/6. It was configured as follows.

That is, a color signal separation unit that separates a color video signal output from a color camera into a luminance signal and a color signal;
A 0 conversion section that converts the luminance signal and color signal, a subsampling section that subsamples the ψ-converted luminance signal and color signal, a switch section that switches the frame memory, and a frame that stores the subsampled data. A memory unit, an encoding processing unit that encodes data in the frame memory, a variable length encoding unit that performs variable length processing on the encoded data, a data transmitting unit that controls communication with the line, and a a control unit that controls the entire process up to transmission processing;
and a memory section for storing programs, a data receiving section that receives data coming next from the line, a variable length decoding processing section that performs variable length decoding processing on the received data, and a variable length decoding processing section that performs variable length decoding processing on the received data. a decoding processing unit that decodes the data that has been processed, a frame memory unit that stores the decoded data, a switch unit that switches the frame memory, an interpolation processing unit that performs interpolation processing on the data in the frame memory, and an interpolation processing unit that performs interpolation processing on the data in the frame memory. The device is configured to include a D/A converter that converts processed digital information into analog information, and a color signal synthesizer that multiplexes the D/A-converted luminance signal and color signal.

(Effect) In order to confirm the effectiveness of the present invention, the following subjective evaluation experiment was conducted to confirm the effect of the present invention.

Image for Evaluation> In this subjective evaluation experiment, GIRL of SIDBA was used as the image for evaluation. The conversion process shown in FIG. 4 was performed on the original image to create 20 images for evaluation.

The ratio of the number of pixels of the luminance signal and the color signal of the created image, the ratio of the number of gradations, and the S/N of the color signal are shown in Table 2 above.

<Evaluation Experiment Method> A subjective evaluation experiment using a disturbance scale was conducted using 20 evaluation images for 10 subjects using four screen sizes (15, 4, 9, and 14-inches). Changing the screen size is equivalent to changing the relative viewing distance.

([Results of subjective evaluation experiment] The results of the subjective evaluation experiment are shown in Figure 5. In Figure 5, the number of gradations ranges from 2 bits (4 levels) to 5 bits (32 levels).
1/Pel) is shown.

Further, FIG. 6 shows the results of the relationship between the number of gradations, the number of pixels, and the subjective evaluation value for each screen size.

From the above results, the following can be understood.

■ The screen size is 4 inches or less and the number of pixels of the brightness signal is 1.
28X128. When the number of pixels of the color difference signal is 16 x 16,
The subjective evaluation value MO8 is 3.

■ The screen size is 4 inches or less, the number of gradations of the luminance signal is s btt (32 levels), and the number of gradations of the color difference signal is 3 b
In the case of it (8 levels), the subjective evaluation value MO8 is 3.

Next, FIG. 7 shows the relationship between the S/N ratio of the color signal of the processed image and the results of the subjective evaluation experiment.

Next, based on the results in Figure 7, the relative viewing distance (aA) and M
FIG. 8 shows the relationship between the S/N of the color signal and the S/N ratio required to ensure OS 3. From the results shown in FIG. 8, it can be seen that as the screen size becomes smaller and the relative viewing distance (d/)() becomes larger, the S side required to obtain MOS 3 may be smaller. In other words, when the screen size is small, the S/N value of the color signal required to obtain the same MOS value as a large screen may be low.

(Example) An example of the present invention will be described with reference to the drawings. FIG. 1a is a block diagram of an embodiment of the present invention.

24 is a color camera, 1 is a color signal separation unit, NTSC
The signal is a color image signal, Y is a luminance signal, and I and Q are color signals. The color image signal NTSC signal inputted from the color camera 24 is separated into a luminance signal Y and color signals I and Q by a color signal separation section 1. 2 is a conversion section, 10 is a subsampling section, 11 is a switch section, and 12 is a frame measurement section.

The luminance signal Y and color signals I and Q are each converted by a ψ conversion unit 2, subjected to subsampling processing by a subsampling unit 10, and stored in the next frame memory unit 12. The switch section 11 at the front stage of the frame memory section 12 has two
This is for switching between two frame memories, ψ
When writing to memory with λ power, another frame memory is in the process of being coded. 13 is the CPU.

14 is an encoding processing unit DPCM, l 5 is FLOM, 1
6 is RAM, Z7 is 5IO118 is Ilo, z9 is V, Cr. The data written in the frame memory section 12 is processed by the CPU 13 and the encoding processing section DPCM14.
CM processing is performed.

In this embodiment, the DPCM processing is performed by hardware, but if the CPU processing capacity is high, it is also possible to perform the processing programmatically. The DPCM-processed data is subjected to variable-length encoding processing in the VC section 19. The variable length coded data is then converted into a transmission format by the SIO processing unit 17.

In some cases, SIO can be processed by an LSI, but if it has a complicated control procedure, it may be possible to process it by dedicated hardware.

An important point in this transmission procedure is that the number of levels after converting the luminance signal Y and the color difference signals I and Q in the converter 2 is different, and the color difference signal ItQ has 1 level in terms of the number of levels compared to the luminance signal Y.
Select a converter so that /4 to IA.

In addition, the subsampling unit 10 reduces the number of pixels in the vertical and horizontal directions of the color signals I and Q with respect to the luminance signal Y from 1/8 to 1/8.
It is necessary to set it to 16.

Next, the processing of the receiving section will be explained. Line transmission line 50
The transmitted virtual data is extracted from the transmission control format by the SIO line control unit 17, and is passed to the variable length decoding circuit 2Q for decoding processing. The decoded data is then processed into DPCM as the next step.
Raw image data is created from the image difference signal by the decoding circuit 21. Image data is stored in frame memory 12
will be written to. The data written to the image frame memory 12 is sent to the next stage interpolation processing unit (Inter Po1a).
tion) 22, interpolation processing between images is executed. Possible methods of interpolation processing include (1) simple interpolation processing, (2) averaging interpolation processing, and the like. FIG. 3 shows an overview of the simple interpolation process and the averaging interpolation process. The data after the interpolation process is converted into an analog signal by the D/A converter 23. The D/A converter 23 uses different luminance signals Y and color signals 1tQ. Next, the D/A converted data is converted into an NTSC signal by a color signal synthesis section 9.

FIG. 1 shows another embodiment of the present invention. FIG. 1 is a block diagram of another embodiment of the present invention. One embodiment of the present invention shown in FIG. 1A and another similar embodiment shown in FIG. . In another embodiment of the present invention shown in FIG. 1, conversion 2 uses the same converter for both the luminance signal and the chrominance signal. In order to change the number of gradations of the luminance signal and color signal, program processing is performed using the following formula.

Ll = INT (KX INT (Lo/K+
0.5) ) Ll: Gradation signal after gradation conversion Lo: Gradation signal of the original signal in the frame memory K: Number of gradation levels required after conversion processing N INT: Rounding down to integer function This process converts the signal into a luminance signal. 1/4 the number of gradations of the color signal for
Let it be IA.

For example, when the luminance signal has 32 gradations, the number of gradations of the color signal is 8 to 5 gradations.

Next, the conversion process of the number of pixels will be explained.

Possible methods for converting the number of pixels include (1) simply thinning out the number of pixels and (2) averaging neighboring pixels.

The process of averaging neighboring pixels is performed by the following process.

M: Number of pixels in matrix LAY: Luminance value of pixels after averaging processing For example, assume that the number of pixels of the luminance signal in the frame memory is 128×128, and the number of pixels of the color signal is 128×128.

The number of pixels of the color signal after the above processing conversion is 16×16. That is, as data, a luminance signal of 128×128, color signals I: 16×16, and Q: 16×16 are transmitted.

FIG. 1C shows a flowchart diagram of another embodiment of the present invention, but detailed description thereof will be omitted.

(Effects of the Invention) As explained above, when transmitting a color image assuming a small screen, the ratio of the color signal to the luminance signal may be smaller than in the past, which has the advantage of being able to transmit in a narrow band. be. In addition, since the number of pixels to be processed in the color image encoding section is smaller than before, the number of pixels to be processed in the encoding section can be reduced.
This has the advantage that the software can be simplified.

[Brief explanation of the drawing]

FIG. 1a is a block diagram of the configuration of one embodiment of the present invention, FIG. 1 is a block diagram of the configuration of another embodiment of the invention, FIG. 1C is a flowchart of another embodiment of the invention, Figure 2 is a block diagram of a conventional color image transmission method, Figure 3 is an explanatory diagram of an example of interpolation processing, Figure 4 is an explanatory diagram of the conversion processing procedure, Figure 5 is an illustration of the results of a subjective evaluation experiment, and Figure 6 is an illustration of the results of a subjective evaluation experiment. FIG. 7 is an explanatory diagram of the relationship between the color signal and the average opinion score. FIG. 8 is an explanatory diagram of the relationship between relative viewing distance and S/N. 1... Color signal separation unit, 2... ψ conversion unit, 3...
- TDM conversion circuit, 4... Encoding circuit, 5... Transmission control circuit, 6... Decoding circuit, 7... TDM inverse conversion circuit, 8... D/A conversion section, 9. ...Color signal synthesis section, 1θ...Subsampling section, 11...Switch section, 12...Frame memory section, 13...CPU
, 14...DPCM encoding processing unit, 15...ROM
% 16...RAM, 17...Transmission control LSI (
SIO), 1 B...I10 control LSI, 2!7
... variable length encoding circuit, 20... variable length encoding circuit, 2... DPCM decoding circuit, 22... interpolation processing section, 23... D/A conversion section, 24...・Color camera, 25... Color monitor camera, 50-... Transmission line,
Y...luminance signal, engineering...color signal, Q...color signal,
MoS: Average opinion score. Patent applicant: Nippon Telegraph and Telephone Corporation Flowchart diagram of another embodiment of the present invention (Figure 1<C) Y: Luminance signal: Color signal Q: Block diagram of a conventional color image transmission method Figure 2 @Simple interpolation processing An explanatory diagram of an example of interpolation processing Fig. 3 A convenient explanatory diagram of conversion processing Fig. 4 MOS MOS 1.5 inch
4-inch subjective evaluation experiment results explanatory diagram Figure 6

Claims (2)

[Claims] (1) In a method that uses a small screen (1.5 to 5 inches) to separate and transmit a color image signal into a luminance signal and a color signal, the number of color signal pixels relative to the number of luminance signal pixels to configure a color image. Increase the ratio from 1/8 to 1/ both vertically and horizontally.
16 and the ratio of the number of color signal gradations to the number of luminance signal gradations to 1/4 to 1/6 before transmission. (2) A color signal separation unit that separates the color video signal output from the color camera into a luminance signal and a color signal, an A/D conversion unit that converts the luminance signal and color signal from A/D, and an A/D converter
A subsampling unit that subsamples the converted luminance signal and color signal, a switch unit that switches frame memories, a frame memory unit that stores subsampled data, and an encoding processing unit that encodes the data in the frame memory. , a variable length encoding unit that performs variable length processing on encoded data, a data transmission unit that controls communication with the line, a control unit that controls the entire process from encoding to transmission processing, and a program. a memory section for storing;
Next, a data receiving unit receives data coming from the line,
A variable length decoding processing section that performs variable length decoding processing on received data, a decoding processing section that decodes the variable length decoded data, and a frame memory section that stores the decoded data. , a switch section that switches the frame memory, an interpolation processing section that performs interpolation processing on data in the frame memory, a D/A conversion section that converts interpolated digital information into analog information, and a D/A converted luminance. A color image transmission processing device comprising a color signal synthesis section that multiplexes a signal and a color signal.