Encoder rate control

• US 7,321,695 B2
• Filed: 12/12/2002
• Issued: 01/22/2008
• Est. Priority Date: 09/21/1994
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Schwartz, Edward L.
• Primary Examiner(s): Tran; Phuoc
• Application Number:
  US10/318,962
• Publication Number:
  US 20030138151A1
• Time in Patent Office: 1,867 Days
• Field of Search: 382/239, 382/251, 348/419.1, 375/240.03
• US Class Current: 382/239
• CPC Class Codes: G06F 17/148 Wavelet transforms
• CPC Class Codes: G06K 15/02 using printers
• CPC Class Codes: G06K 15/1865 by compressing the rasterized print data
• CPC Class Codes: H03M 7/30 Compression speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N; Expansion; Suppression of unnecessary data, e.g. redundancy reduction
• CPC Class Codes: H04N 19/10 using adaptive coding
• CPC Class Codes: H04N 19/102 characterised by the element, parameter or selection affected or controlled by the adaptive coding
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/12 Selection from among a plurality of transforms or standards, e.g. selection between discrete cosine transform [DCT] and sub-band transform or selection between H.263 and H.264
• CPC Class Codes: H04N 19/122 Selection of transform size, e.g. 8x8 or 2x4x8 DCT; Selection of sub-band transforms of varying structure or type
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/129 Scanning of coding units, e.g. zig-zag scan of transform coefficients or flexible macroblock ordering [FMO]
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• CPC Class Codes: H04N 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/156 Availability of hardware or computational resources, e.g. encoding based on power-saving criteria
• CPC Class Codes: H04N 19/162 User input
• CPC Class Codes: H04N 19/167 Position within a video image, e.g. region of interest [ROI]
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/18 the unit being a set of transform coefficients
• CPC Class Codes: H04N 19/184 : the unit being bits, e.g. of the compressed video stream
• CPC Class Codes: H04N 19/186 : the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/1883 : the unit relating to sub-band structure, e.g. hierarchical level, directional tree, e.g. low-high [LH], high-low [HL], high-high [HH]
• CPC Class Codes: H04N 19/36 : Scalability techniques involving formatting the layers as a function of picture distortion after decoding, e.g. signal-to-noise [SNR] scalability
• CPC Class Codes: H04N 19/42 : characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation H04N19/635 takes precedence
• CPC Class Codes: H04N 19/46 : Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/593 : involving spatial prediction techniques
• CPC Class Codes: H04N 19/60 : using transform coding
• CPC Class Codes: H04N 19/61 : in combination with predictive coding
• CPC Class Codes: H04N 19/635 : characterised by filter definition or implementation details
• CPC Class Codes: H04N 19/647 : using significance based coding, e.g. Embedded Zerotrees of Wavelets [EZW] or Set Partitioning in Hierarchical Trees [SPIHT]
• CPC Class Codes: H04N 19/98 : Adaptive-dynamic-range coding [ADRC]
• CPC Class Codes: H04N 21/6377 : directed to server one-way streaming services wherein the source is controlled by the destination H04L65/613
• CPC Class Codes: H04N 21/658 : Transmission by the client directed to the server

Abstract

A method and apparatus for performing compression and/or decompression is described. In one embodiment, the present invention comprises a system having a buffer, a wavelet transform unit, and a coder. The wavelet transform unit has an input coupled to the buffer to perform a wavelet transform on pixels stored therein and to generate coefficients at an output. The coder is coupled to the wavelet transform unit to code the transformed pixels received from the buffer.

Claims

1. A method for performing compression comprising the steps of:

determining the average length of codewords to identify an encoding rate; and

adjusting a compression rate based on a desired amount of compression.

2. The method defined in claim 1 further comprising the step of:

increasing an amount of quantization level if the encoding rate indicates compression is below a first desirable level; and

decreasing the amount of quantization if the encoding rate indicates that compression is above the second desired level.

3. The method defined in claim 2 wherein the first and second desirable levels are not the same.

4. The method of claim 1 wherein the step of determining the average length of codewords is performed after bit generation.

5. The method of claim 1 further comprising the step of signaling a new compression rate to a decoder.

6. The method of claim 5 wherein the signaling is explicit.

7. The method of claim 5 wherein the signaling is implicit.

8. An article of manufacture having at least one readable storage media with executable instructions thereon which, when executed by a processing device, cause the processing device to:

determine the average length of codewords to identify an encoding rate; and

adjust a compression rate based on a desired amount of compression.

9. The article of manufacture defined in claim 8 further comprising executable instructions on the at least one readable storage media which, when executed by the processing device, cause the processing device to:

increase an amount of quantization level if the encoding rate indicates compression is below a first desirable level; and

decrease the amount of quantization if the encoding rate indicates that compression is above the second desired level.

10. The article of manufacture defined in claim 9 wherein the first and second desirable levels are not the same.

11. The article of manufacture defined in claim 8 wherein the processing devices determines the average length of codewords after bit generation.

12. The article of manufacture defined in claim 8 further comprising executable instructions in the at least one readable storage media, which when executed by the processing device, cause the processing device to signal a new compression rate to a decoder.

13. The article of manufacture defined in claim 12 wherein the signaling is explicit.

14. The article of manufacture defined in claim 12 wherein the signaling is implicit.

15. An encoder rate controlling process comprising:

measuring the rate based on average length of coded data units;

determining whether or not the rate indicates that compression is at a desired level; and

controlling quantization on the encoded data.

16. The process defined in claim 15 wherein controlling the quantization performed on the encoded data comprises increasing quantization if the compression is not a desired level.

17. The process defined in claim 15 wherein controlling the quantization performed on the encoded data comprises decreasing quantization if the compression is higher than the desired level.

18. The process defined in claim 15 wherein the rate is measured at predetermined intervals.

19. The process defined in claim 15 further comprising signaling quantization used by the encoder to signal to a decoder the quantization performed during encoding.

20. The process defined in claim 15 further comprising providing the rate to a decoder.

21. The process defined in claim 15 wherein measuring the rate comprises counting the start of coded data units.

22. The process defined in claim 15 wherein measuring the rate comprises counting size of completed coded data units.

23. The process defined in claim 22 wherein counting the size of completed coded data units occurs after bit generation in an entropy encoder.

24. The process defined in claim 15 wherein measuring the rate comprises determining the amount of data written to a channel.

25. An encoder rate controlling process comprising:

measuring the rate wherein measuring the rate comprises counting the start of coded data units, wherein counting the start of coded data units occurs prior to bit generation in an entropy encoder;

determining whether or not the rate indicates that compression is at a desired level; and

controlling quantization on the encoded data.

26. An encoder rate controlling process comprising:

measuring the rate, wherein measuring the rate comprises accumulating an average size of a coded data unit each time a new coded data unit is started;

determining whether or not the rate indicates that compression is at a desired level; and

controlling quantization on the encoded data.

27. An encoder rate controlling apparatus comprising:

means for measuring the rate based on average length of coded data units;

means for determining whether or not the rate indicates that compression is at a desired level; and

means for controlling quantization on the encoded data.

28. The apparatus defined in claim 27 wherein the means for controlling the quantization performed on the encoded data comprises means for increasing quantization if the compression is not a desired level.

29. The apparatus defined in claim 27 wherein the means for controlling the quantization performed on the encoded data comprises means for decreasing quantization if the compression is higher than the desired level.

30. The apparatus defined in claim 27 wherein the rate is measured at predetermined intervals.

31. The apparatus defined in claim 27 further comprising means for signaling quantization used by the encoder to signal to a decoder the quantization performed during encoding.

32. The apparatus defined in claim 27 further comprising means for providing the rate to a decoder.

33. The apparatus defined in claim 27 wherein the means for measuring the rate comprises means for counting the start of coded data units.

34. The apparatus defined in claim 27 wherein the means for measuring the rate comprises means for counting size of completed coded data units.

35. The apparatus defined in claim 34 wherein the means for counting the size of completed coded data units operates after a bit generator in an entropy encoder.

36. The apparatus defined in claim 27 wherein the means for measuring the rate comprises means for determining the amount of data written to a channel.

37. An encoder rate controlling apparatus comprising:

means for measuring the rate wherein the means for measuring the rate comprises means for counting the start of coded data units, wherein the means for counting the start of coded data units operates before a bit generator in an entropy encoder;

means for determining whether or not the rate indicates that compression is at a desired level; and

means for controlling quantization on the encoded data.

38. An encoder rate controlling apparatus comprising:

means for measuring the rate wherein the means for measuring the rate comprises means for counting the start of coded data units, wherein the means for measuring the rate comprises means for accumulating an average size of a coded data unit each time a new coded data unit is started;

means for determining whether or not the rate indicates that compression is at a desired level; and

means for controlling quantization on the encoded data.

39. An article of manufacture having one or more computer-readable storage media which, when executed by a system, causes the system to:

measure the rate based on average length of coded data units;

determine whether or not the rate indicates that compression is at a desired level; and

control quantization on the encoded data.

40. The article of manufacture defined in claim 39 wherein the instructions that cause the system to control the quantization performed on the encoded data comprise instructions which, when executed by the system, cause the system to increase quantization if the compression is not a desired level.

41. The article of manufacture defined in claim 39 wherein the instructions that cause the system to control the quantization performed on the encoded data comprise instructions which, when executed by the system, cause the system to decrease quantization if the compression is higher than the desired level.