JPH07322298A - Coder - Google Patents

Abstract

PURPOSE:To improve the image quality as an entire pattern by decreasing a compression rate of a block whose image quality deterioration is remarkable visually so as to enhance the compression rate of a block whose image quality deterioration is not remarkable. CONSTITUTION:An input digital image signal including a signal Y and signals R-Y and B-Y respectively is block-processed. Then a signal Y discrimination device 307, an signal R discrimination device 308 and a signal B discrimination device 309 check respectively a level of a luminance signal and color difference signals as to the signal Y and signals R-Y and B-Y and Y discrimination information, discrimination information R and discrimination information B are given to a compression controller 310. The compression controller 310 provides an output of a compression control signal to a quantizer 304 based on the three sets of discrimination information. The quantizer 304 controls a compression rate of color difference signals of each block subject to orthogonal transformation adaptively corresponding to each hue and luminance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coding apparatus for reducing visual image quality deterioration and performing high efficiency coding when recording and transmitting a video signal.

[0002]

2. Description of the Related Art Generally, a video signal (image signal) has a very large amount of information. Therefore, when recording or transmitting, there is a method of reducing the amount of information so that the deterioration of the image quality is not noticeable by high efficiency coding. It is used. An orthogonal transform coding device using orthogonal transform coding is generally used as this method.

FIG. 7 is a block diagram showing the structure of a conventional orthogonal transform coding device. The operation will be described below with reference to FIG.
This will be described with reference to FIG. In FIG. 7, a digitally converted image signal is input from an input terminal 1, and a circuit (not shown) divides an image of one screen (one frame) into a plurality of blocks. The blocked image signal is provided to the orthogonal transformer 2. In the orthogonal transformer 2, the image signal is orthogonally transformed by DCT or the like and input to the encoder 3.

The encoder 3 comprises a rearrangement circuit 5, a quantizer 6, a quantization selection circuit 7, and an encoding circuit 8. When the signals of the blocks having the respective orthogonal transform coefficients are output from the orthogonal transformer 2, the signals are rearranged by the rearrangement circuit 5
And the orthogonal transform coefficients are rearranged two-dimensionally. Then, this signal is input to the quantizer 6, and the orthogonal transform coefficient is quantized with a predetermined step width. At this time, the quantization selection circuit 7 selects a quantization coefficient having an optimum step width in order to fit the quantized data amount output from the quantizer 6 into a desired data amount. Next, the encoding circuit 8 assigns shorter code words to the quantized codes, the more frequently occurring codes, and outputs the encoded data to the output terminal 4
Output from.

FIG. 8 shows an orthogonal transform coefficient and rearrangement circuit 5.
It is explanatory drawing which shows the operation | movement. In the figure, (a) shows the output A of the orthogonal transformer 2 and (b) shows the output B of the rearrangement circuit 5, each showing the arrangement of the coefficients in one block. The coefficient array shown in FIG. 8 is a two-dimensional orthogonal transform method of the orthogonal transformer 2 and has a block size of 4 horizontal pixels and 4 vertical pixels. Therefore, the signal A shown in FIG.
In this case, a total of 16 coefficients including 4 horizontal coefficients and 4 vertical coefficients constitute one block.

In the block of FIG. 8, the left side of the frequency component represented by each coefficient represents the horizontal low band component, and the upper portion represents the vertical low band component. In the rearrangement circuit 5,
For the coding for the two-dimensional orthogonal transform, as shown by the coefficient arrangement of the signal B in FIG. 8B, the signals are rearranged in a two-dimensional frequency space called a zigzag scan in the order of low to high frequencies. The reason why such rearrangement is performed is that the lower-frequency component including the direct-current component generally has a greater effect on the visual sense, and therefore this component is treated as an important element. Therefore, the step width (quantization coefficient) of the quantizer 6 is set to increase in order from the lower band of the orthogonal transform coefficient.

[0007]

However, the above conventional structure has the following problems. That is, in the orthogonal transform coding apparatus of the conventional example, the coded data amount is quantized so that it is within a predetermined amount with several blocks as one unit. Therefore, the frequency components are protected as important information on average, and the distribution of the orthogonal transform coefficient spreads from low to high frequencies, blocks with a large amount of data, blocks with high red saturation, etc. It was not possible to allocate a sufficient amount of data to the blocks that were important to the user. Therefore, since the same compression coding is performed on a visually important block, there is a drawback that the image quality is deteriorated.

The present invention has been made in view of the above-mentioned problems of the prior art, and lowers the compression ratio for a block in which image deterioration is visually noticeable, and conversely makes it difficult to visually recognize image deterioration. An object of the present invention is to provide an encoding device capable of improving the image quality of the entire screen by increasing the compression rate for blocks and allocating the reduced amount of data to the other important blocks. And

[0009]

According to a first aspect of the present invention, a luminance signal (Y signal) of an input digital image signal and two color difference signals (RY signal, BY signal) of a predetermined size are set. A blocker that divides the block into blocks, a Y signal determiner that outputs Y determination information based on the brightness level of each pixel of the block of the brightness signal obtained from the blocker, and each block using the Y determination information A compression controller that outputs a compression control signal for controlling the compression ratio of the block, and a high-efficiency encoder that compresses and encodes the output signal of the blocker based on the compression control signal of the compression controller. The compression controller
It is characterized in that the compression rate is increased for the Y signal block judged to be high in brightness by the Y signal judging device and the color difference signal block located at the same position on the screen.

According to the invention of claim 2 of the present application, the Y signal judging device judges that the block having the luminance higher than a predetermined level has a predetermined number or more of pixels in the block to be subjected to the luminance judgment, which is a high luminance block. It is characterized by that.

According to the invention of claim 3 of the present application, the Y signal determiner determines that the high brightness block is used when the average value of the brightness levels of all pixels in the Y signal block to be brightness determined is equal to or greater than a specified value. It is characterized by determining that.

According to the invention of claim 4 of the present application, the high-efficiency encoder includes an orthogonal transformer which receives the signal of the blocker and performs orthogonal transformation of the image signal, and a block which is orthogonally transformed by the orthogonal transformer. A quantizer that performs quantization by selecting the quantization step width based on the compression control signal of the compression controller so that the code amount is equal to or less than the specified code amount, and a code that encodes the output data of the quantizer. And a rectifier.

According to a fifth aspect of the present invention, the luminance signal (Y signal) of the input digital image signal and the two color difference signals (RY) are used.
Signal, BY signal) is divided into blocks of a predetermined size, and R signal determination for outputting R determination information based on the color difference signal of the block of the RY color difference signal obtained from the blocker And the B-obtained from the blocker
Using a B signal determiner that outputs B determination information based on the color difference signal of the Y color difference signal block, and a compression control signal for controlling the compression ratio of each block using the R determination information and the B determination information And a high efficiency encoder that compresses and encodes the output of the blocker based on the compression control signal of the compression controller. The compression controller is at the same position on the screen. A combination of R determination information and B determination information, which is determination information of two color difference signal blocks, determines unique color difference determination information for two color difference signal blocks, and the two color difference signals are determined using the color difference determination information. By determining the compression control signal of the block, the compression ratio is adaptively controlled in accordance with the hue.

In the invention of claim 6 of the present application, the R signal judging device and the B signal judging device confirm that the number of pixels having a color difference of a predetermined level or more is equal to or more than a prescribed number in the block to be subjected to the R judgment and the B judgment. It is characterized in that it is used as a criterion.

According to the invention of claim 7 of the present application, the R signal judging device and the B signal judging device judge that the average value of the color differences of all the pixels is equal to or more than a prescribed value in the block to be subjected to the R judgment and the B judgment. It is characterized by making it a standard.

In the invention of claim 8 of the present application, the R signal judging device and the B signal judging device are characterized in that a plurality of sets of judgment reference values of color difference levels are set.

In the invention of claim 9 of the present application, a plurality of sets of judgment reference values of the color difference level are set in the R signal judgment device and the B signal judgment device, and the reference is made for the RY signal and the BY signal. It is characterized by different values.

According to the invention of claim 10 of the present application, the high-efficiency encoder includes an orthogonal transformer for inputting the signal of the blocker and performing orthogonal transformation of the image signal, and a block orthogonally transformed by the orthogonal transformer. A quantizer that performs quantization by selecting the quantization step width based on the compression control signal of the compression controller so that the code amount is equal to or less than the specified code amount, and a code that encodes the output data of the quantizer. And a rectifier.

According to the eleventh aspect of the present invention, the compression controller sets the compression signal to the low compression rate even for the color difference signal set to the low compression rate and the luminance signal of the block located at the same position on the screen. It is characterized by outputting a control signal.

According to a twelfth aspect of the present invention, a luminance signal (Y signal) of the input digital image signal and two color difference signals (R
-Y signal, BY signal) is divided into blocks of a predetermined size, and R-obtained from the blocker
An R signal determiner that outputs R determination information based on the color difference signal of the Y color difference signal block, and a B signal that outputs B determination information based on the color difference signal of the BY color difference signal block obtained from the blocker Blocking is performed based on the compression controller, which outputs a compression control signal for controlling the compression ratio of each block using the R determination information and the B determination information, and the compression control signal of the compression controller. And a high-efficiency encoder that compresses and encodes the output of the output device. The compression controller includes R determination information and B determination information which are determination information of blocks of two color difference signals located at the same position on the screen. It is characterized by adaptively controlling the red compression ratio by determining the compression control signal of the block of the RY signal in combination.

In the thirteenth aspect of the invention of the present application, the R signal judging device and the B signal judging device confirm that the number of pixels having a color difference of a predetermined level or more is equal to or more than a prescribed number in the block to be subjected to the R judgment and the B judgment. It is characterized in that it is used as a criterion.

In the fourteenth aspect of the invention of the present application, the R signal judging device and the B signal judging device determine that the average value of the color difference levels of all pixels is equal to or more than a specified value in the block to be subjected to the R judgment and the B judgment. It is characterized in that it is used as a criterion.

According to a fifteenth aspect of the present invention, the R signal judging device and the B signal judging device are characterized in that a plurality of sets of judgment reference values of color difference levels are set.

In the sixteenth aspect of the invention of the present application, the R signal judging device and the B signal judging device are set with a plurality of sets of judgment reference values of the color difference level, and the reference is made for the RY signal and the BY signal. It is characterized by different values.

In the seventeenth aspect of the present invention, the high-efficiency encoder includes an orthogonal transformer for inputting the signal of the blocker and performing orthogonal transformation of the image signal, and a block orthogonally transformed by the orthogonal transformer. A quantizer that performs quantization by selecting the quantization step width based on the compression control signal of the compression controller so that the code amount is equal to or less than the specified code amount, and a code that encodes the output data of the quantizer. And a rectifier.

According to the eighteenth aspect of the present invention, the compression controller sets the red compression difference signal set to a low compression rate and the luminance signal of the block located at the same position on the screen to a low compression rate. And outputting a compression control signal for

According to a nineteenth aspect of the present invention, a luminance signal (Y signal) of an input digital image signal and two color difference signals (R-
(Y signal, BY signal) is divided into blocks of a predetermined size, and a luminance level is obtained for each pixel of a block of luminance signals obtained from the blocker.
A Y signal determiner that outputs Y determination information, an R signal determiner that outputs R determination information based on a color difference signal of a block of an RY color difference signal obtained from a blocker, and a B signal obtained from the blocker. -A B signal determiner that outputs B determination information based on a color difference signal of a block of a Y color difference signal, and a Y determination information, an R determination information, and a B determination information, for controlling the compression ratio of each block. A compression controller that outputs a compression control signal, and a high efficiency encoder that compression-encodes the output of the blocker based on the compression control signal of the compression controller,
The compression controller is provided with a combination of the Y determination information, the R determination information, and the B determination information, which are the determination information of the blocks of the luminance signal and the two color difference signals located at the same position on the screen, of the two color difference signals. By determining unique color difference determination information for each block and determining the compression control signal of the block of two color difference signals using the color difference determination information, it is possible to adaptively control the compression ratio corresponding to the hue. It is a feature.

According to the twentieth aspect of the invention of the present application, the Y signal judging device, the R signal judging device and the B signal judging device have pixels of a predetermined level or higher in the blocks to be subjected to the Y judgment, the R judgment and the B judgment. It is characterized in that the criterion is that the number is equal to or more than a prescribed number.

In the twenty-first aspect of the invention of the present application, the Y signal judging device, the R signal judging device, and the B signal judging device are the averages of the levels of all pixels in the blocks to be subjected to the Y judgment, the R judgment, and the B judgment. It is characterized in that the criterion is that the value is greater than or equal to the specified value.

According to a twenty-second aspect of the present invention, the R signal judging device and the B signal judging device are characterized in that a plurality of sets of judgment reference values of color difference levels are set.

In the invention of claim 23 of the present application, the R signal judging device and the B signal judging device are set with plural sets of judgment reference values of the color difference level, and the reference is made for the RY signal and the BY signal. It is characterized by different values.

According to the twenty-fourth aspect of the present invention, the high-efficiency encoder includes an orthogonal transformer for inputting the signal of the blocker and performing orthogonal transformation of the image signal, and a block orthogonally transformed by the orthogonal transformer. A quantizer that performs quantization by selecting the quantization step width based on the compression control signal of the compression controller so that the code amount is equal to or less than the specified code amount, and a code that encodes the output data of the quantizer. And a rectifier.

According to the twenty-fifth aspect of the present invention, the compression controller sets the compression signal to the low compression rate even for the color difference signal set to the low compression rate and the luminance signal of the block located at the same position on the screen. It is characterized by outputting a control signal.

According to a twenty-sixth aspect of the present invention, a luminance signal (Y signal) of an input digital image signal and two color difference signals (R-
(Y signal, BY signal) is divided into blocks of a predetermined size, and a Y signal for outputting Y determination information by checking the luminance level of each pixel of the block of the luminance signal obtained from the blocker Judgment device, R signal judgment device which outputs R judgment information based on the color difference signal of the block of the RY color difference signal obtained from the blocker, and color difference between blocks of the BY color difference signal obtained from the blocker Compression control for outputting a compression control signal for controlling the compression ratio of each block using a B signal determiner that outputs B determination information based on a signal and Y determination information, R determination information, and B determination information And a high-efficiency encoder that compresses and encodes the output signal of the blocker based on the compression control signal of the compression controller, and the compression controller is a luminance signal at the same position on the screen. And two color difference Y is a determination information blocks
By combining the judgment information, the R judgment information, and the B judgment information, R
A feature is that the red compression rate is adaptively controlled by determining the quantization control signal of the -Y signal block.

According to the twenty-seventh aspect of the present invention, the Y signal judging device, the R signal judging device, and the B signal judging device have pixels of a predetermined level or higher in the blocks to be subjected to the Y judgment, the R judgment, and the B judgment. It is characterized in that the criterion is that the number is equal to or more than a prescribed number.

In the twenty-eighth aspect of the invention of the present application, the Y signal determiner, the R signal determiner, and the B signal determiner are the averages of the levels of all pixels in the blocks to be subjected to the Y determination, the R determination, and the B determination. It is characterized in that the criterion is that the value is greater than or equal to the specified value.

In the invention of claim 29 of the present application, the R signal judging device and the B signal judging device are characterized in that a plurality of sets of judgment reference values of color difference levels are set.

In the invention of claim 30 of the present application, the R signal judging device and the B signal judging device are set with a plurality of sets of judgment reference values of the color difference level, and the reference is made for the RY signal and the BY signal. It is characterized by different values.

In the thirty-first aspect of the invention of the present application, the high-efficiency encoder includes an orthogonal transformer for inputting the signal of the blocker and performing orthogonal transformation of the image signal, and a block orthogonally transformed by the orthogonal transformer. A quantizer that performs quantization by selecting the quantization step width based on the compression control signal of the compression controller so that the code amount is equal to or less than the specified code amount, and a code that encodes the output data of the quantizer. And a rectifier.

According to the thirty-second aspect of the present invention, the compression controller sets the RY color difference signal set to the low compression rate and the luminance signal of the block at the same position on the screen to the low compression rate. It is characterized by outputting a compression control signal to be set.

[0041]

According to the inventions of claims 1 to 4 having the above characteristics, when the input digital image signal is inputted to the blocker, the luminance signal and the two color difference signals respectively have predetermined magnitudes. Divided into blocks. The luminance signal determiner checks the luminance level of each pixel in the block and outputs Y determination information. The compression controller uses this Y determination information to output a compression control signal that controls the compression ratio of the block. For the block of the color difference signal located at the same position as the block determined to be high in luminance by the luminance signal determiner, the compression controller gives the high efficiency encoder a compression control signal for increasing the compression rate. In this way, the code amount of the hue that is visually inconspicuous is reduced, and the amount of assigned information for important pixel information is increased.

Further, according to the inventions of claims 5 to 18 of the present application,
When the input digital image signal is input to the blocker,
The luminance signal and the two color difference signals are each divided into blocks of a predetermined size. The R signal determiner checks the contents of the block of the red color difference signal to make a determination, and outputs R determination information. Further, the B signal determiner checks the contents of the block of the blue color difference signal to make a determination, and outputs B determination information. The compression controller uses the R judgment information and the B judgment information to give a compression control signal to the high efficiency encoder. In this way, unique color difference determination information is determined by the combination of the determination information of the two color difference signals located at the same position on the screen, and this information is used to control the compression ratio of the blocks of the two color difference signals. Then, the code amount of the red or blue hue is reduced.

Further, according to the inventions of claims 19 to 32 of the present application, in addition to the inventions of claims 5 to 18, a Y signal judging device is also provided. The compression controller uses Y judgment information, R judgment information, and B judgment information.
The compression control signal is provided to the high efficiency encoder using the decision information. The compression controller adaptively controls the operation of the high-efficiency encoder centering on the compression ratio of red for two blocks of color difference signals located at the same position on the screen. In this way, the image quality is improved without increasing the amount of image information of the entire screen to be transmitted.

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An encoding apparatus in each embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of an encoding device according to the first embodiment of the present invention. In the figure, the blocker 102 is an input terminal 10
A circuit that divides each of the luminance signal (Y signal) and the two color difference signals (RY signal, BY signal) of the 1-frame digitized image signal input from 1 into a plurality of blocks. is there. The signal blocked by the blocker 102 is provided to the orthogonal transformer 103 and the Y signal determiner 107. The orthogonal transformer 103 is a circuit that orthogonally transforms the input image signal of each block by, for example, DCT, and outputs an orthogonal transform coefficient (hereinafter, simply referred to as transform coefficient) corresponding to each frequency component.

The transform coefficient of the orthogonal transformer 103 is the quantizer 1
04 and the compression controller 108. Quantizer 10
Reference numeral 4 denotes a circuit for quantizing the input signal with a predetermined step width, and a plurality of sets of its quantization characteristics are prepared, and the compression controller 108 indicates a quantization coefficient as a compression control signal. The encoder 105 inputs the code of the quantizer 104, assigns a shorter codeword to a code having a higher occurrence frequency, and outputs the coded data from the output terminal 109. Here, the orthogonal transformer 103, the quantizer 104, and the encoder 105 configure a high-efficiency encoder 106 that compresses the total code amount or information amount of the input image signal to generate a band-compressed image signal. is doing.

The Y signal judging device 107 is a circuit for judging the luminance (Y) level of the image in each block. There are, for example, two types of brightness level determination methods, and one method is to count the number of pixels having a brightness value of a predetermined value or more from the brightness values of the pixels included in one block. If this number is greater than or equal to the specified value, it is determined as a high-luminance block. In another method, the average value of the brightness of all pixels is calculated, and if the average value is equal to or more than a specified value, it is determined as a high brightness block. The compression controller 108 is the Y signal judging device 10.
It is a circuit that determines the compression ratio for each block based on the determination result of 7. The compression controller 108 outputs the compression control signal to the quantizer 104 to select a particular quantization characteristic.

The operation of the coding apparatus of the first embodiment constructed as above will be described. The digital image signal input from the input terminal 101 is given to the blocker 102 and converted into a block of a coding unit. Then, the blocked image signal is processed by the high-efficiency encoder 106 and the Y signal determiner 1.
It is output to 07. In the high-efficiency encoder 106, the orthogonal transformer 103 orthogonally transforms the input image signal and rearranges the transform coefficients. Then, the signal is quantized by the quantizer 10
4 and the compression controller 108.

On the other hand, the Y signal judging device 107 has a high luminance depending on whether or not there are a predetermined number or more of pixels having a level equal to or higher than a threshold value for the block of the Y signal which is the luminance signal of the input image. It is determined whether the block is a block of. The determination result here is given to the compression controller 108. The compression controller 108 determines the compression rate using the determination result of the Y signal determination unit 107 and the output spectrum of the orthogonal transformer 103, and outputs the compression control signal to the quantizer 104.

When determining this compression rate, the compression rate of the block of the color difference signal located at the same position on the screen as the block determined to be a high-luminance block by the Y signal determination unit 107 is set to a value higher than usual. Set higher. The quantizer 104 performs quantization according to the compression control signal input from the compression controller 108 so as to select the quantization step width so that the encoded data fits within a predetermined code amount. And the encoder 105
Encodes the input data and outputs an encoded signal from the output terminal 109 in which the data transfer rate is controlled to be constant regardless of the content of the input image.

As described above, in the first embodiment, the Y signal determination unit 107 determines the block of the high-luminance Y signal, and the compression controller 108 increases the compression rate of the color difference signals at the same position on the screen. . As a result, it is possible to reduce the code amount of the block of the color difference signal corresponding to the block of the high-luminance Y signal that is difficult to visually recognize. By doing so, the amount of data corresponding to that can be allocated to other blocks, and the image quality of the entire screen can be further improved.

In this embodiment, the Y signal judging device 10
As the determination method of 7, if the average value of the levels of the pixels in the Y signal block is equal to or higher than a predetermined level, it is possible to use a high-luminance block, and the determination is performed using the data after orthogonal transformation. It is also possible to do so. Further, there may be a plurality of blocks of the luminance signal at the same position as the color difference signal due to the relationship between the sampling frequencies of the luminance signal and the color difference signal. In such a case, a plurality of blocks having high luminance may be included. A high compression rate may be set when there are a predetermined number or more of blocks.

Next, the encoding devices in the second and third embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing the overall configuration of the encoding devices of the second and third embodiments. Similar to the first embodiment, the input terminals 201,
Blocker 202, orthogonal transformer 203, quantizer 20
4, an encoder 205, and an output terminal 210 are provided, and their functions are the same, so description thereof will be omitted.

Unlike the first embodiment, the R signal determiner 20
7, a B signal determiner 208 and a compression controller 209 for inputting the determination results of these determiners are provided respectively. R
The signal determiner 207 is a color difference signal RY for the image signal of each block output from the blocker 202.
This is a circuit that determines the level of a signal. Similarly, the B signal determiner 208 is also a circuit that determines the level of the BY signal with respect to the image signal of each block output from the blocker 202.

FIG. 3 is an explanatory diagram showing the determination methods of the R signal determiner 207 and the B signal determiner 208. Let Tha and Thb (Tha> Thb) be the threshold values of each hue, and R (red)
If the number of pixels equal to or greater than Tha is equal to or greater than a, the determination result Ra is output as R determination information. If the number of pixels of Thb or less is b or more, the determination result Rc is output as the R determination information. And in other cases, the judgment result R
Output b. The same applies to B (blue), and the determination results Ba, Bc, and Bb are output for threshold values Tha or more, Thb or less, and other cases, respectively.

The compression controller 209 has an R signal judging unit 207.
And when the determination result is input from the B signal determiner 208,
Unique RB determination information is determined for both color difference (R and B) blocks, and the compression ratio for the color difference signal is determined using this RB determination information and the data of the transform coefficient of the orthogonal transformer 203 to perform compression control. It is a circuit that outputs a signal to the quantizer 204.

The operation of the coding apparatus of the second embodiment having such a configuration will be described. When the digital image signal input from the input terminal 201 is supplied to the blocker 202, it is divided into blocks of coding units. The blocked image signal is output to the high-efficiency encoder 206, the R signal determiner 207, and the B signal determiner 208. In the high efficiency encoder 206, the orthogonal transformer 2
Reference numeral 03 performs orthogonal transformation of image signals in block units and rearranges transformation coefficients. The quantizer 20
4 and the compression controller 209.

R signal determiner 207 and B signal determiner 208
Makes a determination as shown in FIG. 3, for example, for each block of the RY signal and the BY signal that are color difference signals. That is, the frequency distribution of the levels of the color difference signals is examined under the condition that a predetermined number or more of pixels having a level equal to or higher than a certain threshold value are included in the pixels in each block. Then, the results are used as R determination information and B determination information, respectively, in the compression controller 2
It outputs to 09. For example, as shown in FIG. 4, the compression controller 209 uses the input R determination information and B determination information to determine unique RB determination information from 9 combinations for both color difference blocks. And the compression controller 20
9 uses the RB determination information and the output of the orthogonal transformer 203 to determine the compression ratio of each color difference signal and supplies the compression control signal to the quantizer 204. The subsequent signal processing is the same as in the first embodiment.

As described above, in the second embodiment, the judgment information obtained by the R signal judgment unit 207 and the B signal judgment unit 208 is used to determine the judgment information unique to each color difference signal, and based on the judgment information. To determine the compression rate of each color difference signal. As a result, the compression rate can be adaptively controlled according to the hue, and the compression rate can be changed according to the visual recognition degree of image quality deterioration. Therefore, when encoding is performed within a fixed code amount, the assigned code amount can be effectively used, so that the image quality of the entire screen can be improved.

Next, the operation of the coding apparatus in the third embodiment will be described. In FIG. 2, the digital image signal input from the input terminal 201 is processed in exactly the same way as in the second embodiment in the process up to the compression controller 209A. In the compression controller 209A, as in the second embodiment, for example, as shown in FIG.
The RB determination information RBa to RBi is determined using the determination information. Then, the compression controller 209A determines the compression rate of the RY signal using the RB determination information and the output of the orthogonal transformer 203, and outputs the compression control signal to the quantizer 204. The subsequent signal processing is the same as in the second embodiment.

As described above, in the third embodiment, the determination information obtained by the R signal determination unit 207 and the B signal determination unit 208 is used to determine the unique determination information, and then the compression rate of the RY signal is calculated. decide. From the viewpoint of visual recognition of image deterioration,
The RY signal is the dominant color difference signal. Since red is highly recognized by humans, even if only red is protected, the same effect as in the second embodiment can be obtained, and the circuit scale can be reduced as compared with the case of the second embodiment.

In the second and third embodiments, the determination methods of the R signal determiner 207 and the B signal determiner 208 are:
When the average value of the pixel level in each signal block is equal to or higher than a predetermined level, it can be determined as a high-luminance block or can be determined by using the data after orthogonal transformation. is there. The number of thresholds and their levels in the R signal determiner 207 and the B signal determiner 208 are arbitrary, and the thresholds may differ between the RY signal and the BY signal. Further, by further reducing the compression rate of both the color difference signal block for which the compression rate is set low and the luminance signal block at the same position on the screen, it is possible to perform more effective encoding.

Next, the encoding devices in the fourth and fifth embodiments of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram showing the overall configuration of the encoding devices of the fourth and fifth embodiments. Similar to the second and third embodiments, the input terminal 30
1, the blocker 302, the orthogonal transformer 303, the quantizer 304, the encoder 305, the R signal determiner 307, the B signal determiner 309, and the output terminal 310 are provided, and their functions are the same. Therefore, the description is omitted.

The Y signal determining unit 307 is for the Y signal block which is the luminance signal of the input video signal, while the R signal determining unit 308 and the B signal determination 309 are R- which are the color difference signals of the input video signal. For each block of the Y signal and the BY signal, for example, as shown in FIGS. 3 and 6, respectively, if the number of pixels having a level equal to or higher than the threshold value, which is the pixel in each block, is equal to or more than a predetermined number. The determination is performed under the condition that there is, and the results are output to the compression controller 310 as Y determination information, R determination information, and B determination information, respectively.

Different from the second and third embodiments, the blocker 3
A Y signal judging device 30 similar to that of the first embodiment is provided at the output terminal of 02.
7 is provided. The compression controller 310 inputs the determination results of the Y signal determiner 307, the R signal determiner 308, and the B signal determiner 309, respectively, and based on these three determination results, unique RB determination for both color difference blocks. It is a circuit that determines information. This RB determination information is given to the quantizer 304 as a compression control signal.

The operation of the thus-configured coding apparatus according to the fourth embodiment will be described. When the digital image signal input from the input terminal 301 is input to the blocker 302, it is divided into blocks of coding units. The blocked image signal is output to the high efficiency encoder 306,
The signal is output to the Y signal determiner 307, the R signal determiner 308, and the B signal determiner 309. In the high-efficiency encoder 306, the orthogonal transformer 303 orthogonally transforms the blocked image signal and rearranges the transform coefficients. Then, this signal is given to the quantizer 304 and the compression controller 310.

The Y signal judging device 307 judges the inputted Y signal block as shown in FIG. That is, the threshold of the brightness level of each pixel is set to Thx, Thx, T
When hz (Thx>Thy> Thz) is set and the number of pixels Thx or more is x or more, the determination result Yx is output as Y determination information. If the number of pixels of Thy or more is y or more, the determination result Yy is output as Y determination information, and T
If the number of pixels of hz or more is z or more, the determination result Yz is output as Y determination information. In other cases, the determination result Yo is output.

R signal determiner 308 and B signal determiner 309
Is a predetermined number or more of pixels having a level equal to or higher than a certain threshold value as shown in FIG. 3 for each block of the RY signal and the BY signal which are input color difference signals. Determination is made on the condition that the result is R determination information,
It outputs to the compression controller 310 as B determination information. The compression controller 310 determines the unique RB determination information shown in FIG. 45 for both color difference blocks based on the input three determination information. Then, the compression controller 310 determines the compression rate of each color difference signal from the RB determination information and the output of the orthogonal transformer 303, and outputs the compression control signal to the quantizer 304. The subsequent processing is the same as in the first and second embodiments.

As described above, in the fourth embodiment, the judgment information obtained by the Y signal judgment unit 307, the R signal judgment unit 308, and the B signal judgment unit 309 is used to determine unique judgment information for each color difference signal. Then, the compression rate of each color difference signal is determined based on the determination information. As a result, it is possible to deal with the level of the luminance signal, and it is possible to perform finer control than in the second embodiment. For this reason, the compression rate can be changed more adaptively in accordance with the degree of visual recognition of image quality deterioration. Therefore, the improvement effect is greater than in the case of the second embodiment.

Next, the operation of the coding apparatus in the fifth embodiment will be described. In FIG. 5, the digital image signal input from the input terminal 301 is processed in exactly the same way as in the fourth embodiment in the process up to the compression controller 310. The compression controller 310 determines RB determination information by the same method as in the fourth embodiment, and determines the RB determination information and the orthogonal transformer 30.
The output of No. 3 is used to determine the compression ratio of the RY signal and the compression control signal is output to the quantizer 304. The subsequent processing is the same as in the fourth embodiment.

As described above, in the fifth embodiment, by using the determination information obtained by the Y signal determination unit 307, the R signal determination unit 308, and the B signal determination unit 309, the determination information unique to the RY signal is given. After determining, the compression rate of the block of the RY signal is determined. Thus, for the same reason as in the case of the third embodiment, even if only the red color is protected, the same effect as that of the fourth embodiment can be obtained, and the circuit scale is reduced as compared with the case of the fourth embodiment.

In the fourth and fifth embodiments, the Y signal judging device 307, the R signal judging device 308, and the B signal judging device 30.
As the determination method of No. 9, it is possible to set a block in which the average value of the pixel levels in each signal block is equal to or higher than a predetermined level as a high-luminance block, and use the data after orthogonal transformation to make the determination. It is also possible to do so. Further, the number and level of thresholds in the R signal determiner 308 and the B signal determiner 309 are arbitrary, and the thresholds may be different between the RY signal and the BY signal. Further, by further reducing the compression rate of the block of the color difference signal for which the compression rate is set low and the block of the luminance signal at the same position on the screen, it is possible to perform more effective encoding. In this example,
An encoder that does not use an orthogonal transformer can be used as the high-efficiency encoder, and the compression rate can be set by the compression controller without using the output of the orthogonal transformer.

[0072]

As described above, the coding apparatus of the present invention selects a portion whose image quality deterioration is hard to be visually recognized to increase the compression rate, and conversely sets the compression rate of the portion where visual deterioration is easily recognized. The image quality of the entire screen can be improved without increasing the information amount of the image. Moreover,
Only by adding a simple circuit to the conventional coding device, a great effect of improving the image quality can be obtained, and the practical effect thereof is great.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an encoding device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an encoding device according to second and third embodiments of the present invention.

FIG. 3 is an explanatory diagram showing operations of an R signal determiner and a B signal determiner of each embodiment.

FIG. 4 is an explanatory diagram showing the operation of the compression controller in the second to fifth embodiments of the present invention.

FIG. 5 is a block diagram showing a configuration of an encoding device according to fourth and fifth embodiments of the present invention.

FIG. 6 is an explanatory diagram showing the operation of the Y signal judging device in the fourth and fifth embodiments.

FIG. 7 is a block diagram showing a configuration example of a conventional encoding device.

FIG. 8 is an explanatory diagram showing an operation of a rearrangement circuit in the encoding device.

[Explanation of symbols]

 101, 201, 301 Input terminal 102, 202, 302 Blocker 103, 203, 303 Orthogonal transformer 104, 204, 304 Quantizer 105, 205, 305 Encoder 106, 206, 306 High efficiency encoder 107 , 307 Y signal determiner 207, 308 R signal determiner 208, 309 B signal determiner 108, 209, 310 Compression controller 109, 210, 310 Output terminal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 7/30

Claims (32)

[Claims] 1. A blocker for dividing a luminance signal (Y signal) and two color difference signals (RY signal, BY signal) of an input digital image signal into blocks of a predetermined size, and the blocker. A Y signal determiner that outputs Y determination information based on the luminance level of each pixel of the block of the luminance signal obtained from the device, and a compression control signal for controlling the compression ratio of each block using the Y determination information. A compression controller that outputs, based on a compression control signal of the compression controller, a high efficiency encoder that compression-encodes the output signal of the blocker,
The compression controller increases a compression rate for a block of a color difference signal located at the same position on the screen as a block of the Y signal determined to have high brightness by the Y signal determiner. An encoding device characterized by the above. 2. The Y signal judging device judges as a high-luminance block when there are a prescribed number or more of pixels having a luminance of a predetermined level or higher in the block to be subjected to luminance judgment. The encoding device according to item 1. 3. The Y signal judging device judges as a high-luminance block when the average value of the luminance levels of all pixels in the Y-signal block to be subjected to luminance judgment is equal to or more than a specified value. The encoding device according to claim 1. 4. The high-efficiency encoder is configured such that a signal from the blocker is input, an orthogonal transformer that performs orthogonal transformation of an image signal, and a code amount of a block that has been orthogonally transformed by the orthogonal transformer,
A quantizer that performs quantization by selecting a quantization step width based on a compression control signal of the compression controller so as to be equal to or less than a specified code amount, and an encoder that encodes output data of the quantizer The encoding device according to claim 1, wherein the encoding device comprises: 5. A blocker for dividing a luminance signal (Y signal) and two color difference signals (RY signal, BY signal) of an input digital image signal into blocks of a predetermined size, and the blocker. R signal determiner that outputs R determination information based on the color difference signal of the block of the RY color difference signal obtained from the block, and B based on the color difference signal of the block of the BY color difference signal obtained from the blocker. A B signal determiner that outputs determination information; a compression controller that outputs a compression control signal for controlling the compression ratio of each block using the R determination information and B determination information; A high-efficiency encoder that compresses and encodes the output of the blocker based on a compression control signal, the compression controller determining blocks of two color difference signals located at the same position on the screen. R judgment that is information The combination of the information and the B determination information determines unique color difference determination information for the two color difference signal blocks, and the color difference determination information is used to determine the compression control signal for the two color difference signal blocks. Accordingly, the encoding device is characterized in that the compression rate is adaptively controlled according to the hue. 6. The R signal determiner and the B signal determiner are based on a criterion that the number of pixels having a color difference of a predetermined level or more is equal to or more than a prescribed number in a block to be subjected to the R determination and the B determination. The coding apparatus according to claim 5, wherein the coding apparatus is present. 7. The R signal judging device and the B signal judging device use a judgment criterion that an average value of color differences of all pixels in a block to be subjected to the R judgment and the B judgment is a specified value or more. The encoding device according to claim 5, wherein 8. The code according to claim 5, wherein the R signal determiner and the B signal determiner are set with a plurality of sets of determination reference values of color difference levels. Device. 9. The R signal judging device and the B signal judging device are set with a plurality of sets of judgment reference values of color difference levels.
9. The encoding device according to claim 5, wherein the −Y signal and the BY signal have different reference values. 10. The high-efficiency encoder is configured such that a signal from the blocker is input, an orthogonal transformer that performs orthogonal transformation of an image signal, and a code amount of a block that has been orthogonally transformed by the orthogonal transformer,
A quantizer that performs quantization by selecting a quantization step width based on a compression control signal of the compression controller so as to be equal to or less than a specified code amount, and an encoder that encodes output data of the quantizer The encoding device according to claim 5, further comprising: 11. The compression controller outputs a compression control signal for setting a low compression rate to a luminance signal of a block located at the same position on the screen as a color difference signal set to a low compression rate. The encoding device according to claim 5, characterized in that: 12. A luminance signal (Y
Signal) and two color difference signals (RY signal, BY signal) into blocks of a predetermined size, and a color difference signal of the block of RY color difference signals obtained from the blocker. An R signal determiner that outputs R determination information based on the above, a B signal determiner that outputs B determination information based on the color difference signal of the block of the BY color difference signal obtained from the blocker, and the R determination A compression controller that outputs a compression control signal for controlling the compression ratio of each block using the information and the B determination information, and an output of the blocker based on the compression control signal of the compression controller. A high-efficiency encoder for compression-encoding, wherein the compression controller is a combination of the R determination information and the B determination information, which is determination information of blocks of two color difference signals located at the same position on the screen. The RY signal By determining the compression control signal click, the encoding apparatus characterized by adaptively controlling the red compressibility. 13. The R signal determiner and the B signal determiner use, as a criterion, the number of pixels having a color difference of a predetermined level or more in a predetermined number or more in a block to be subjected to the R determination and the B determination. The coding device according to claim 12, wherein the coding device is present. 14. The R signal determiner and the B signal determiner use, as a criterion for determination, an average value of color difference levels of all pixels in a block to be subjected to R and B determinations is a specified value or more. The coding device according to claim 12, wherein the coding device is present. 15. The code according to claim 12, wherein the R signal determiner and the B signal determiner have a plurality of sets of determination reference values of color difference levels. Device. 16. The R signal determiner and the B signal determiner are provided with a plurality of sets of color difference level determination reference values.
The encoding device according to any one of claims 12 to 14, wherein the −Y signal and the BY signal have different reference values. 17. The high-efficiency encoder receives a signal from the blocker as an orthogonal transformer for orthogonally transforming an image signal, and a code amount of a block orthogonally transformed by the orthogonal transformer,
A quantizer that performs quantization by selecting a quantization step width based on a compression control signal of the compression controller so as to be equal to or less than a specified code amount, and an encoder that encodes output data of the quantizer The encoding device according to claim 12, further comprising: 18. The compression controller outputs a compression control signal for setting a low compression ratio even for a luminance signal of a block located at the same position on the screen as a red color difference signal set for a low compression ratio. 13. The method according to claim 12, wherein
Encoding device described. 19. A luminance signal (Y
Signal) and two color difference signals (RY signal, BY signal) into blocks of a predetermined size, and a luminance level for each pixel of the block of luminance signals obtained from the blocker. A Y signal determiner that outputs Y determination information based on the above, and an R signal determiner that outputs R determination information based on the color difference signal of the block of the RY color difference signal obtained from the blocker; Of the B-Y color difference signal obtained from the B / Y color difference signal of the block based on the color difference signal of the block, and the Y determination information, the R determination information, and the B determination information. A compression controller that outputs a compression control signal for controlling the compression rate, and a high efficiency encoder that compression-encodes the output of the blocker based on the compression control signal of the compression controller. Then Serial compressor controller, the Y determination information and R judgment information and B on the screen is a luminance signal and determination information of the blocks of the two color difference signals in the same position
The combination of the determination information determines the unique color difference determination information for the two color difference signal blocks, and the color difference determination information is used to determine the compression control signal for the two color difference signal blocks to obtain the hue. An encoding device characterized by adaptively controlling the compression rate in accordance with the above. 20. The Y signal determiner, the R signal determiner, and the B signal determiner each have a predetermined number or more of pixels of a predetermined level or higher in a block to be subjected to Y determination, R determination, and B determination. 20. The encoding device according to claim 19, characterized in that 21. The Y signal determiner, the R signal determiner, and the B signal determiner are such that the average value of the levels of all pixels is equal to or more than a specified value in a block to be subjected to Y determination, R determination, and B determination. 20. The encoding apparatus according to claim 19, wherein the determination criterion is that there is. 22. The code according to claim 19, wherein the R signal determiner and the B signal determiner are set with a plurality of sets of color difference level determination reference values. Device. 23. In the R signal judging device and the B signal judging device, a plurality of sets of judgment reference values of color difference levels are set, and
The encoding device according to any one of claims 19 to 22, wherein the reference values of the -Y signal and the BY signal are different. 24. The high-efficiency encoder, wherein the signal of the blocker is input, an orthogonal transformer that performs orthogonal transformation of an image signal, and a code amount of a block that is orthogonally transformed by the orthogonal transformer,
A quantizer that performs quantization by selecting a quantization step width based on a compression control signal of the compression controller so as to be equal to or less than a specified code amount, and an encoder that encodes output data of the quantizer 20. The encoding apparatus according to claim 19, further comprising: 25. The compression controller outputs a compression control signal for setting a low compression rate to a luminance signal of a block located at the same position on the screen as a color difference signal set to a low compression rate. 20. The encoding device according to claim 19, wherein: 26. A luminance signal (Y
Signal) and two color difference signals (RY signal, BY signal) into blocks of a predetermined size, and a luminance level for each pixel of a block of luminance signals obtained from the blocker. And a Y signal determiner that outputs Y determination information, an R signal determiner that outputs R determination information based on the color difference signal of the block of the RY color difference signal obtained from the blocker, and the blocking Compressing each block using a B signal determiner that outputs B determination information based on the color difference signal of the block of BY color difference signal obtained from the device, and the Y determination information, R determination information, and B determination information. A compression controller that outputs a compression control signal for controlling the rate, based on the compression control signal of the compression controller, a high-efficiency encoder that compression-encodes the output signal of the blocker,
The compression controller includes the Y determination information, the R determination information, and the B determination information, which are determination information of blocks of a luminance signal and two color difference signals located at the same position on the screen.
An encoding device which adaptively controls the compression ratio of red color by determining a quantization control signal of a block of an RY signal based on a combination of determination information. 27. The Y signal determiner, the R signal determiner, and the B signal determiner each have a predetermined number or more of pixels of a predetermined level or higher in a block to be subjected to Y determination, R determination, and B determination. 27. The encoding device according to claim 26, characterized in that 28. The Y signal determiner, the R signal determiner, and the B signal determiner are such that the average value of the levels of all pixels is equal to or more than a specified value in a block to be subjected to Y determination, R determination, and B determination. 27. The encoding device according to claim 26, wherein the determination criterion is that there is. 29. The code according to claim 26, wherein the R signal determiner and the B signal determiner are set with a plurality of sets of color difference level determination reference values. Device. 30. A plurality of sets of color difference level judgment reference values are set in the R signal judging device and the B signal judging device.
30. The encoding apparatus according to claim 26, wherein the −Y signal and the BY signal have different reference values. 31. The high-efficiency encoder is configured such that a signal from the blocker is input, an orthogonal transformer that performs orthogonal transformation of an image signal, and a code amount of a block that is orthogonally transformed by the orthogonal transformer,
A quantizer that performs quantization by selecting a quantization step width based on a compression control signal of the compression controller so as to be equal to or less than a specified code amount, and an encoder that encodes output data of the quantizer 27. The encoding apparatus according to claim 26, further comprising: 32. The compression controller sets a compression control signal to be set to a low compression rate even for a luminance signal of a block located at the same position on the screen as the RY color difference signal set to a low compression rate. It outputs, It is characterized by the above-mentioned.
6. The encoding device according to item 6.