JPH10108170A - High efficiency coder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the high efficiency coder in which image quality is always kept constant independently of a complicated input image and the image quality is optionally controlled. SOLUTION: A coding section 7 applies compression processing to image data 1 and provides an output of coded data 2. A transmission buffer 8 stores tentatively the coded data 2. A coding control section 9 provides an output of a compression rate control signal 5 with a buffer occupancy signal 4 denoting an amount of data stored in a transmission buffer 8. A transmission rate control section 10 outputs a buffer read clock 6 of a frequency based on the compression rate control signal 5 and allows the transmission buffer 8 to output transmission data 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-efficiency coding apparatus, and more particularly to a high-efficiency coding apparatus which controls a compression rate by a coding amount to perform high-efficiency image transmission and high-density image recording.

[0002]

2. Description of the Related Art A conventional high-efficiency encoding apparatus writes band-compressed data in a buffer memory in order to keep the amount of generated information constant, reads the data at a predetermined line speed or a recording speed on a medium after writing, and The compression rate is controlled based on the remaining amount of data in the buffer memory to equalize the amount of generated information. Examples of such high-efficiency coding include "image signal multiplexing method" described in JP-A-58-145284, "video signal storage device" described in JP-A-7-236119, and JP-A-4-181887. An "image encoding / decoding device" described in Japanese Patent Application Laid-Open Publication No. H10-209686 is known. In the "image signal multiplexing method" described in Japanese Patent Application Laid-Open No. 58-145284, even when a plurality of images are encoded and the data is multiplexed and transmitted, the amount of data generated by the encoder is stored in the buffer memory. The transmission rate is detected so that the transmission rate of a system having a large storage amount is increased. That is, the control of the compression ratio and the speed of reading from the buffer memory are controlled by the comparison value of each image with the remaining amount of data in the buffer memory, and the line speed after multiplexing, that is, the amount of generated information is kept constant.

Also, in the "video signal storage device" described in Japanese Patent Application Laid-Open No. 7-236119, when a writing error to a recording medium occurs, the reading from the buffer memory is stopped, and the compressed signal processing is performed based on the remaining amount of data in the buffer memory. The means for controlling the compression ratio for each section is employed.

On the other hand, in the "picture coding / decoding apparatus" described in Japanese Patent Application Laid-Open No. Hei 4-181887, feedback is given to coding by comparing the amount of compression-coded codes with a preset externally set transmission rate. I do.

[0005]

The above-mentioned conventional high-efficiency coding apparatus places a technical point of view on improving the transmission efficiency or the recording efficiency. Therefore, the remaining amount of data in the buffer memory or the coding per frame is considered. Feedback is based on the amount of data and used as a reference for compression control. For this reason, control is performed so that the difference in the amount of generated information due to the complexity of the input image, that is, the difference in pattern or motion, is kept constant. doing.

Further, since the data is fed back to the encoding unit based on the remaining amount of data in the buffer memory, the speed of reading data from the buffer memory changes, so that it is difficult to arbitrarily control the image quality. have.

An object of the present invention is to provide a high-efficiency coding apparatus which can always keep the image quality constant irrespective of the complexity of an input image and can arbitrarily control the image quality.

[0008]

A high-efficiency encoding apparatus according to the present invention stores encoded data obtained by band-compressing image data, and determines a compression ratio of the band compression based on the amount of encoded data. In addition to the control, the reading speed of the stored encoded data is controlled and the transmission data is output.

Encoding means for band-compressing image data;
Transmission storage means for storing encoded data output by the encoding means, outputting a storage amount occupation signal, and outputting transmission data in accordance with a transmission clock; controlling the compression ratio of the image data by the storage amount occupation signal Encoding means for outputting a compression rate control signal to the encoding means; and transmission rate control means for outputting the transmission clock in accordance with the compression rate control signal.

Encoding means for band-compressing the image data;
Transmission storage means for storing encoded data output by the encoding means, outputting a storage amount occupation signal, and outputting transmission data in accordance with a transmission clock; controlling the compression ratio of the image data by the storage amount occupation signal Encoding control means for outputting a compression rate control signal to the encoding means; subtracter for subtracting the compression rate control signal from a reference compression rate signal and outputting a subtraction signal; transmission clock based on the subtraction signal And transmission speed control means for outputting

An upper limit value and a lower limit value are set for the frequency of the transmission clock output by the transmission speed control means.

The band compression performed by the encoding means is orthogonal transformation processing.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of a high efficiency coding apparatus according to the present invention.

The present embodiment shown in FIG.
An encoding unit 7 for compressing the data and outputting encoded data 2;
A transmission buffer 8 for temporarily storing the encoded data 2 and an encoding control unit 9 for outputting a compression ratio control signal 5 based on a buffer occupancy signal 4 indicating the amount of data stored in the transmission buffer 8
And a transmission rate control unit 10 that controls the transmission rate of the transmission data 3 read from the transmission buffer 8 based on the compression ratio control signal 5 by a buffer read clock 6.

FIG. 2 is a diagram for explaining the operation of the present embodiment.

Next, the operation of this embodiment will be described in more detail with reference to FIGS.

The input image data 1 is data-compressed by an encoding unit 7 and is transmitted as encoded data 2 into a transmission buffer 8.
Is stored. Here, for data compression, for example, orthogonal transformation processing such as two-dimensional discrete cosine transformation (DCT) is applied.

The transmission buffer 8 outputs a buffer occupancy signal 4 indicating the stored data amount to the encoding control unit 9. Upon receiving the buffer occupancy signal 4, the encoding control unit 9 outputs a compression ratio control signal 5 for setting a compression ratio to the encoding unit 7 and the transmission rate control unit 10. The encoding control unit 9 receives the buffer occupancy signal 4 indicating the increase in the amount of data stored in the transmission buffer 8, and increases the data compression ratio when the buffer occupancy increases. Is controlled so as to suppress the amount of generated data 2.

On the other hand, the transmission rate control unit 10 also uses the compression ratio control signal 5 to increase the data reading speed from the transmission buffer 8 if the compression ratio is high, and to decrease the data reading speed if the compression ratio is low. The buffer read clock 6 is output to the transmission buffer 8 as described above.

Referring to FIG. 2, it is understood how the buffer occupancy, the compression ratio and the buffer read speed change. That is, pattern 1 shows an example in which the buffer read speed is controlled, and pattern 2 shows an example in which the buffer occupancy and the compression ratio change when the buffer read speed is constant.

In the case of pattern 1, the amount of change in the buffer occupancy is suppressed within a certain range by adjusting the read speed of the buffer read clock 6, and as a result, the amount of change in the compression ratio is suppressed, so that the image quality is kept constant. Has an effect. On the other hand, in the case of the pattern 2, since the read speed of the buffer read clock 6 is fixed, if the occupancy of the buffer is large, the compression ratio is unconditionally increased and image quality is degraded.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

In FIG. 3, components corresponding to those shown in FIG. 1 are denoted by the same reference numerals or symbols, and description thereof is omitted.

Referring to FIG. 3, when the image data 1 is compression-encoded by the encoding unit 7 and the encoded data 2 is stored in the transmission buffer 8, the transmission buffer 8 indicates a buffer occupancy indicating the amount of stored data. The amount signal 4 is encoded by the encoding control unit 9
Output to The encoding control unit 9 generates and outputs a compression ratio control signal 5 so as to increase the compression ratio when the occupancy of the buffer increases and to decrease the compression ratio when the occupancy of the buffer decreases.

The compression rate control signal 5 is compared with a reference compression rate signal 11 set in advance by a subtracter 12, and a subtraction output signal 13 indicating the difference is output to a transmission rate control unit 10 to control the transmission rate. . That is, the transmission rate control unit 10
Controls the clock frequency of the buffer read clock 6 for reading data from the transmission buffer 8 by the subtraction output signal 13. If the subtraction signal 13 is positive, the frequency of the buffer read clock 6 is increased, and if the subtraction signal 13 is negative, the frequency of the buffer read clock 6 is decreased.

However, the clock frequency of the buffer read clock 6 is limited so that the clock frequency falls within the range between the bit rate upper limit signal 14 and the bit rate lower limit signal 15.

FIG. 4 is a diagram for explaining the operation of the embodiment of FIG.

Referring to FIG. 4, it is understood how the buffer occupancy, the compression ratio and the buffer read speed change. That is, when the compression ratio exceeds the reference compression ratio, the buffer reading speed increases, and when the compression ratio becomes lower than the reference compression ratio, the buffer reading speed decreases. However, the compression rate is limited within a specified range by the upper and lower limits of the bit rate of the transmission speed.

In order to control the image quality, it is necessary to control the buffer reading speed of the transmission buffer 8. However, since the amount of compression-coded data depends on the complexity of the image, in order to keep the image quality constant, It is necessary to set the data buffer reading speed in consideration of the complexity of the image.

The compression processing performed by the encoding unit 7 includes discrete cosine transform, Hadamard transform, Fourier transform, K
Orthogonal transformation processing such as L transformation and DPCM transformation processing are applied.

[0032]

As described above, the high-efficiency coding apparatus of the present invention increases or decreases the compression ratio control signal obtained from the comparison with the reference compression ratio signal, thereby increasing or decreasing the data reading speed from the buffer memory. Since the change in the occupation amount can be suppressed, there is an effect that image quality deterioration due to compression processing for a complicated image is inconspicuous.

Also, since the speed of reading data from the buffer memory is controlled based on the compression ratio,
This has the effect that the image quality can be arbitrarily controlled.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a high efficiency coding apparatus according to the present invention.

FIG. 2 is a diagram illustrating the operation of the present embodiment.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram for explaining the operation of the embodiment of FIG. 3;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image data 2 encoded data 3 transmission data 4 buffer occupancy signal 5 compression ratio control signal 6 buffer read clock 7 encoding unit 8 transmission buffer 9 encoding control unit 10 transmission speed control unit 11 reference compression ratio signal 12 subtractor 13 Subtraction output signal 14 Bit rate upper limit signal 15 Bit rate lower limit signal

Claims (5)

[Claims] 1. A method for storing coded data obtained by band-compressing image data, controlling a compression rate of the band compression based on the amount of coded data, and controlling a reading speed of the stored coded data. A high-efficiency encoding device which controls and outputs transmission data. Encoding means for band-compressing image data; storing encoded data output by the encoding means;
Transmission storage means for outputting a storage amount occupation signal and outputting transmission data in accordance with a transmission clock; encoding for outputting to the encoding means a compression ratio control signal for controlling a compression ratio of the image data in accordance with the storage amount occupation signal Control means;
Transmission rate control means for outputting the transmission clock in accordance with the compression rate control signal. Encoding means for band-compressing the image data; storing encoded data output by the encoding means;
Transmission storage means for outputting a storage amount occupation signal and outputting transmission data in accordance with a transmission clock; encoding for outputting to the encoding means a compression ratio control signal for controlling a compression ratio of the image data in accordance with the storage amount occupation signal Control means;
A subtractor for subtracting the compression ratio control signal from a reference compression ratio signal and outputting a subtraction signal; and transmission speed control means for outputting the transmission clock in accordance with the subtraction signal. Efficiency coding device. 4. The high-efficiency coding apparatus according to claim 3, wherein an upper limit value and a lower limit value are set for a frequency of said transmission clock output by said transmission rate control means. 5. The high-efficiency coding apparatus according to claim 2, wherein the band compression performed by said coding means is orthogonal transform processing.