Image encoding apparatus and method, program, and storage medium

• US 20030118240A1
• Filed: 11/19/2002
• Published: 06/26/2003
• Est. Priority Date: 12/25/2001
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Naito, Satoshi, Satoh, Makoto, Chiba, Yukio
• Granted Patent: US 7,106,909 B2
• Time in Patent Office: Days
• US Class Current: 382/239
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/192 the adaptation method, adaptation tool or adaptation type being iterative or recursive
• CPC Class Codes: H04N 19/196 being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters processing of motion vectors H04N19/513
• CPC Class Codes: H04N 19/60 using transform coding

Abstract

An encoder (103) encodes image data using a first parameter Q1, and a re-encoder (107) re-encodes the encoded result of the encoder (103) using a second parameter Q2. When the encoded data size obtained by the encoder (103) exceeds a predetermined size, Q1 is replaced by Q2, and encoded data streams previously encoded by the re-encoder (107) are saved in a buffer (108) as those encoded by the encoder (103) after the parameter is changed. Upon executing a re-encoding process, the re-encoder (107) re-encodes encoded data streams previously encoded by the re-encoder (107) using a parameter that can assure a higher compression ratio than Q2.

Claims

1. An image encoding method for compression-encoding image data, comprising:

the first compression-encoding step of compression-encoding image data using a first compression-encoding parameter, which can be changed, and generating a compression-encoded encoded data stream;

the re-compression-encoding step of re-compression-encoding the encoded data stream compression-encoded in the first compression-encoding step and an encoded data stream of a substitution candidate, which was compression-encoded by itself previously, using a second compression-encoding parameter which is generated in accordance with the first compression-encoding parameter applied to the first compression-encoding step, and of generating an encoded data stream of a substitution candidate, which is compression-encoded at a higher compression ratio;

the data size determination step of counting a data size of an encoded data stream, which is compression-encoded in the first compression-encoding step, and determining if the data size is not less than a predetermined size;

the change step of replacing, when it is determined in the data size determination step that the data size of the encoded data stream compression-encoded in the first compression-encoding step is not less than the predetermined size, the first compression-encoding parameter by the second compression-encoding parameter;

the save step of saving, when it is determined in the data size determination step that the data size of the encoded data stream compression-encoded in the first compression-encoding step is not less than the predetermined size, the encoded data stream of the substitution candidate, which was previously compression-encoded in the re-compression-encoding step, as an encoded data stream compression-encoded in the first compression-encoding step after the first encoding parameter is changed, and of saving the encoded data stream, which is compression-encoded in the first compression-encoding step after the first compression-encoding parameter is changed, as a subsequent encoded data stream;

the process execution selection step of selecting, when it is determined in the data size determination step that the data size of the encoded data stream compression-encoded in the first compression-encoding step is not less than the predetermined size, if a re-compression-encoding process in the re-compression-encoding step is to be executed; and

update step of updating, when it is selected in the process execution selection step that the re-compression-encoding process in the re-compression-encoding step is to be executed, the second compression-encoding parameter to be applied to the re-compression-encoding step to a new compression-encoding parameter, which can compress data at a higher compression ratio.

3. The method according to claim 1, wherein the first and second compression-encoding parameters are scaling factors for quantized transform coefficients.

4. The method according to claim 1, wherein an encoded data stream that follows the encoded data stream to be saved in the save step is generated in the first compression-encoding step using the changed first compression-encoding parameter.

5. The method according to claim 1, wherein the process execution selection step comprises predicted value calculation step of calculating a predicted value of a probability indicating if it is saved in the save step that the encoded data stream of substitution candidates, which was previously compression-encoded in the re-compression-encoding means, as an encoded data stream compression-encoded in the first compression-encoding step after the parameter is changed, and

it is selected in the process execution selection step that based on the predicted value calculated in the predicted value calculation step if the re-compression-encoding process in the re-compression-encoding step is to be executed.

7. The method according to claim 1, wherein it is calculated in the data size determination step, as the predetermined size, a target encoded data size in accordance with a region of the image data, which is to be compression-encoded in the first compression-encoding step, and determines if the data size of the encoded data stream obtained in the first compression-encoding step is not less than the target encoded data size.

9. The method according to claim 1, wherein the data size determination step includes the step of calculating, as the predetermined size, the target number of symbols, using the number of symbols of the encoded data stream compression-encoded in the first compression-encoding step, and the number of symbols of the encoded data stream of the substitution candidate compression-encoded in the re-compression-encoding step, and of determining if the number of symbols of the encoded data stream compression-encoded in the first compression-encoding step or the number of symbols of the encoded data stream of the substitution candidate compression-encoded in the re-compression-encoding step is not less than the target number of symbols.

13. A program for making a computer implement an image encoding method of claim 1.

14. A computer readable storage medium storing a program of claim 13.

2. An image encoding method for compression-encoding image data, comprising:

the first compression-encoding step of compression-encoding image data using a first compression-encoding parameter, which can be changed, and generating a compression-encoded encoded data stream;

the second compression-encoding step of compression-encoding image data using a second compression-encoding parameter which is generated in accordance with the first compression-encoding parameter applied to the first compression-encoding step, and of generating an encoded data stream of a substitution candidate, which is compression-encoded at a higher compression ratio;

the re-compression-encoding step of re-compression-encoding the encoded data stream of the substitution candidate, which is compression-encoded in the second compression-encoding step, and an encoded data stream of a substitution candidate, which was compression-encoded by itself previously, using the second compression-encoding parameter applied to the second compression-encoding step, and of generating an encoded data stream of a substitution candidate, which is compression-encoded at a higher compression ratio;

the data size determination step of counting a data size of an encoded data stream, which is compression-encoded in the first compression-encoding step, and determining if the data size is not less than a predetermined size;

the change step of replacing, when it is determined in the data size determination step that the data size of the encoded data stream compression-encoded in the first compression-encoding step is not less than the predetermined size, the first compression-encoding parameter by the second compression-encoding parameter;

the save step of saving, when it is determined in the data size determination step that the data size of the encoded data stream compression-encoded in the first compression-encoding step is not less than the predetermined size, the encoded data streams of the substitution candidates, which were previously compression-encoded in the second compression-encoding step and the re-compression-encoding step, as an encoded data stream compression-encoded in the first compression-encoding step after the first encoding parameter is changed, and of saving the encoded data stream, which is compression-encoded in the first compression-encoding step after the first compression-encoding parameter is changed, as a subsequent encoded data stream;

the process execution selection step of selecting, when it is determined in the data size determination step that the data size of the encoded data stream compression-encoded in the first compression-encoding step is not less than the predetermined size, if a compression-encoding process in the second compression-encoding step and a re-compression-encoding process in the re-compression-encoding step are to be executed; and

update step of updating, when it is selected in the process execution selection step selects that the compression-encoding process in the second compression-encoding step and the re-compression-encoding process in the re-compression-encoding step are to be executed, the second compression-encoding parameter to be applied to the second compression-encoding step and the re-compression-encoding step to a new compression-encoding parameter, which can compress data at a higher compression ratio.

6. The method according to claim 2, wherein the process execution selection step comprises the predicted value calculation step of calculating a predicted value of a probability indicating if the encoded data stream is saved in the save step, which was previously compression-encoded in the second compression-encoding step and the re-compression-encoding step, as an encoded data stream compression-encoded in the first compression-encoding step after the parameter is changed, and it is selected in the process execution selection step that based on the predicted value calculated in the predicted value calculation step if the compression-encoding process in the second compression-encoding step and the re-compression-encoding process in the re-compression-encoding step are to be executed.

8. The method according to claim 6, wherein it is calculated in the data size determination step that a plurality of predicted values in accordance a region of the image data, which is to be compression-encoded in the first compression-encoding step, and calculates the target encoded data size using the plurality of predicted values.

10. The method according to claim 2, wherein the data size determination step includes the step of calculating, as the predetermined size, the target number of symbols, using the number of symbols of the encoded data stream compression-encoded in the first compression-encoding step, and the number of symbols of the encoded data stream of the substitution candidate compression-encoded in the second compression-encoding step and the re-compression-encoding step, and of determining if the number of symbols of the encoded data stream compression-encoded in the first compression-encoding step or the number of symbols of the encoded data stream of the substitution candidate compression-encoded in the second compression-encoding step and the re-compression-encoding step is not less than the target number of symbols.

11. An image encoding apparatus for compression-encoding image data, comprising:

first compression-encoding means for compression-encoding image data using a first compression-encoding parameter, which can be changed, and generating a compression-encoded encoded data stream;

re-compression-encoding means for re-compression-encoding the encoded data stream compression-encoded by said first compression-encoding means and an encoded data stream of a substitution candidate, which was compression-encoded by itself previously, using a second compression-encoding parameter which is generated in accordance with the first compression-encoding parameter applied to said first compression-encoding means, and for generating an encoded data stream of a substitution candidate, which is compression-encoded at a higher compression ratio;

data size determination means for counting a data size of an encoded data stream, which is compression-encoded by said first compression-encoding means, and determining if the data size is not less than a predetermined size;

change means for, when said data size determination means determines that the data size of the encoded data stream compression-encoded by said first compression-encoding means is not less than the predetermined size, replacing the first compression-encoding parameter by the second compression-encoding parameter;

save means for, when said data size determination means determines that the data size of the encoded data stream compression-encoded by said first compression-encoding means is not less than the predetermined size, saving the encoded data stream of the substitution candidate, which was previously compression-encoded by said re-compression-encoding means, as an encoded data stream compression-encoded by said first compression-encoding means after the first encoding parameter is changed, and for saving the encoded data stream, which is compression-encoded by said first compression-encoding means after the first compression-encoding parameter is changed, as a subsequent encoded data stream;

process execution selection means for, when said data size determination means determines that the data size of the encoded data stream compression-encoded by said first compression-encoding means is not less than the predetermined size, selecting if are-compression-encoding process by said re-compression-encoding means is to be executed; and

update means for, when said process execution selection means selects that the re-compression-encoding process by said re-compression-encoding means is to be executed, updating the second compression-encoding parameter to be applied to said re-compression-encoding means to a new compression-encoding parameter, which can compress data at a higher compression ratio.

12. An image encoding apparatus for compression-encoding image data, comprising:

first compression-encoding means for compression-encoding image data using a first compression-encoding parameter, which can be changed, and generating a compression-encoded encoded data stream;

second compression-encoding means for compression-encoding image data using a second compression-encoding parameter which is generated in accordance with the first compression-encoding parameter applied to said first compression-encoding means, and for generating an encoded data stream of a substitution candidate, which is compression-encoded at a higher compression ratio;

re-compression-encoding means for re-compression-encoding the encoded data stream of the substitution candidate, which is compression-encoded by said second compression-encoding means, and an encoded data stream of a substitution candidate, which was compression-encoded by itself previously, using the second compression-encoding parameter applied to said second compression-encoding means, and for generating an encoded data stream of a substitution candidate, which is compression-encoded at a higher compression ratio;

data size determination means for counting a data size of an encoded data stream, which is compression-encoded by said first compression-encoding means, and determining if the data size is not less than a predetermined size;

change means for, when said data size determination means determines that the data size of the encoded data stream compression-encoded by said first compression-encoding means is not less than the predetermined size, replacing the first compression-encoding parameter by the second compression-encoding parameter;

save means for, when said data size determination means determines that the data size of the encoded data stream compression-encoded by said first compression-encoding means is not less than the predetermined size, saving the encoded data streams of the substitution candidates, which were previously compression-encoded by said second compression-encoding means and said re-compression-encoding means, as an encoded data stream compression-encoded by said first compression-encoding means after the first encoding parameter is changed, and for saving the encoded data stream, which is compression-encoded by said first compression-encoding means after the first compression-encoding parameter is changed, as a subsequent encoded data stream;

process execution selection means for, when said data size determination means determines that the data size of the encoded data stream compression-encoded by said first compression-encoding means is not less than the predetermined size, selecting if a compression-encoding process by said second compression-encoding means and a re-compression-encoding process by said re-compression-encoding means are to be executed; and

update means for, when said process execution selection means selects that the compression-encoding process by said second compression-encoding means and the re-compression-encoding process by said re-compression-encoding means are to be executed, updating the second compression-encoding parameter to be applied to said second compression-encoding means and said re-compression-encoding means to a new compression-encoding parameter, which can compress data at a higher compression ratio.

15. An image encoding method of compression-encoding image data, comprising:

the first compression-encoding step of compression-encoding image data using a first compression-encoding parameter, which can be changed;

the second compression-encoding step of compression-encoding the compression-encoded results of the first compression-encoding step using a second compression-encoding parameter which can compress data at a higher compression ratio than the first compression-encoding parameter and can be changed;

the determination step of counting a data size of an encoded data stream, which is compression-encoded in the first compression-encoding step, and determining if the data size is not less than a predetermined size;

the change step of replacing, every time it is determined in the determination step that the data size of the encoded data stream obtained in the first compression-encoding step is not less than the predetermined size, the first compression-encoding parameter by the second compression-encoding parameter, and changing the second compression-encoding parameter to a parameter used to obtain a higher compression ratio;

the save step of saving, when it is determined in the determination step that the data size of the encoded data stream obtained in the first compression-encoding step is not less than the predetermined size, an encoded data stream, which was previously compression-encoded in the second compression-encoding step, as encoded data stream compression-encoded in the first compression-encoding step after the parameter is changed;

the re-compression-encoding step of re-compression-encoding, when it is determined in the determination step that the data size of the encoded data stream obtained in the first compression-encoding step is not less than the predetermined size, the encoded data stream, which was previously compression-encoded in the second compression-encoding step, using the second compression-encoding parameter, which is changed in the change step; and

the control step of controlling, when it is determined or predicted in the determination step that the data size of the encoded data stream obtained in the first compression-encoding step is not less than the predetermined size before the re-compression-encoding process of the re-compression-encoding step is completed, the first compression-encoding step to abort a compression-encoding process.

16. The method according to claim 15, wherein the first and second compression-encoding parameters are scaling factors for quantized transform coefficients.

17. The method according to claim 15, wherein an encoded data stream that follows the encoded data stream to be saved in the save step is generated in the first compression-encoding step using the changed first compression-encoding parameter.

18. The method according to claim 15, wherein an encoded data stream that follows the encoded data streams re-compression-encoded in the re-compression-encoding step is generated in the second compression-encoding step using the changed second compression-encoding parameter.

20. A program for making a computer implement an image encoding method of claim 15.

21. A computer readable storage medium storing a program of claim 20.

19. An image encoding apparatus for compression-encoding image data, comprising:

first compression-encoding means for compression-encoding image data using a first compression-encoding parameter, which can be changed;

second compression-encoding means for compression-encoding the compression-encoded results of said first compression-encoding means using a second compression-encoding parameter which can compress data at a higher compression ratio than the first compression-encoding parameter and can be changed;

determination means for counting a data size of an encoded data stream, which is compression-encoded by said first compression-encoding means, and determining if the data size is not less than a predetermined size;

change means for, every time said determination means determines that the data size of the encoded data stream obtained by said first compression-encoding means is not less than the predetermined size, replacing the first compression-encoding parameter by the second compression-encoding parameter, and changing the second compression-encoding parameter to a parameter used to obtain a higher compression ratio;

save means for, when said determination means determines that the data size of the encoded data stream obtained by said first compression-encoding means is not less than the predetermined size, saving an encoded data stream, which was previously compression-encoded by said second compression-encoding means, as encoded data stream compression-encoded by said first compression-encoding means after the parameter is changed;

re-compression-encoding means for, when said determination means determines that the data size of the encoded data stream obtained by said first compression-encoding means is not less than the predetermined size, re-compression-encoding the encoded data stream, which was previously compression-encoded by said second compression-encoding means, using the second compression-encoding means parameter, which is changed by said change means; and

control means for, when said determination means determines or predicts that the data size of the encoded data stream obtained by said first compression-encoding means is not less than the predetermined size before the re-compression-encoding process of said re-compression-encoding means is completed, controlling said first compression-encoding means to abort a compression-encoding process.