Digital image encoding

• US 20040156550A1
• Filed: 07/29/2003
• Published: 08/12/2004
• Est. Priority Date: 07/29/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Fudge, Brian, Thyagarajan, Kadayam, Govindaswamy, Senthil, Irvine, Ann C.
• Granted Patent: US 7,856,149 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 19/122 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 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• 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 19/176 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 19/194 involving only two passes
• 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 19/197 including determination of the initial value of an encoding parameter H04N19/56 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 19/60 using transform coding
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 21/4312 involving specific graphical features, e.g. screen layout, special fonts or colors, blinking icons, highlights or animations
• CPC Class Codes: H04N 21/4314 for fitting data in a restricted space on the screen, e.g. EPG data in a rectangular grid
• CPC Class Codes: H04N 21/440254 by altering signal-to-noise parameters, e.g. requantization
• CPC Class Codes: H04N 21/4405 involving video stream decryption
• CPC Class Codes: H04N 21/4621 Controlling the complexity of the content stream or additional data, e.g. lowering the resolution or bit-rate of the video stream for a mobile client with a small screen arrangements for using the results of monitoring on user's side in broadcast systems H04H60/65; flow control in packet networks H04L47/10
• CPC Class Codes: H04N 21/4623 Processing of entitlement messages, e.g. ECM [Entitlement Control Message] or EMM [Entitlement Management Message] arrangements for conditional access to broadcast information or to broadcast-related services H04H60/14
• CPC Class Codes: H04N 21/84 Generation or processing of descriptive data, e.g. content descriptors systems specially adapted for using meta-information in broadcast systems H04H60/73
• CPC Class Codes: H04N 7/17318 : Direct or substantially direct transmission and handling of requests

Abstract

An apparatus and method for limiting bit rate of compressed data is disclosed. The apparatus and method allows the generation of parameters for encoding digital image data based on the data bit rate resulting from the use of different parameters. In one embodiment, a statistical analysis is performed to determine the different parameters. The use of parameters results in a bit rate that would prevent a decoder to stall during decompression while allowing the encoder compress without affecting the quality. Therefore, a more efficient encoding and decoding can be achieved.

Claims

1. An apparatus comprising:

a source generator configured to convert image information into digital image information; and

an encoder coupled to the source generator, the encoder configured to receive the digital image information from the source generator and comprising;

a parameter generator to output at least a first set of parameters;

a first image compressor coupled to the parameter generator, the first image compressor to compress the digital image information using the first set of parameters.

2. The apparatus of claim 1, wherein the parameter generator comprises:

a second image compressor to compress the digital information using a second set of parameters;

a processor coupled to the first and second image compressors, the processor to output the second set of parameters, the processor to adjust the second set of parameters and output a third set of parameters as the second set of parameters, if the use of the second set of parameters results in a selected data bit rate, and otherwise, to output the second set of parameters as the first set of parameters.

3. The apparatus of claim 2, wherein the parameter generator further comprises:

a statistic generator coupled to the processor, the statistic generator configured to generate a statistical analysis; and

wherein

the processor adjusts the second set of parameters based on the statistical analysis.

4. The apparatus of claim 1, wherein the parameter generator comprises:

a processor to output the first set of parameters, the processor to adjust the first set of parameters to generate a second set of parameters if the use of the first set of parameters results in a selected data bit rate, and to output the second set of parameters as the first set of parameters.

5. The apparatus of claim 4, wherein the parameter generator further comprises:

a statistic generator coupled to the processor, the statistic generator configured to generate a statistical analysis; and

wherein

the processor adjusts the first set of parameters based on the statistical analysis.

6. The apparatus of claim 5, wherein the statistical analysis involves analyzing bits per pixel for images.

7. The apparatus of claim 5, wherein the statistical analysis determines the effectiveness of the first set of parameters.

8. The apparatus of claim 1, wherein the first set of parameters includes Q-steps and the first image compressor comprises:

a transform module to convert the digital image information from spatial to frequency domain, the transform module to generate transform coefficients;

a quantization module to quantize the transform coefficients using the Q-steps; and

a variable length coding module to compress the quantized transform coefficients.

9. The apparatus of claim 8, wherein the first set of parameters further includes frequency weight mask (FWM) tables and the quantization module to quantize the transform coefficients using FWM tables and Q-steps.

10. The apparatus of claim 8, wherein the first set of parameters further includes a Huffman code tables and the variable length coding module includes a Huffman engine to compress the quantized transform coefficients using the Huffman code tables.

11. The apparatus of claim 8, wherein the first set of parameters further includes an adaptive block size discrete transform (ABSDCT) threshold and the transform module comprises an ABSDCT module to convert the digital image information from spatial to frequency domain using ABSDCT according to the ABSDCT threshold.

12. The apparatus of claim 1, wherein the digital image information is at least a portion of a film.

13. A method for encoding digital image information comprising:

generating and outputting at least a first set of parameters;

compressing the digital image information using the first set of parameters; and

adjusting the first set of parameters to generate a second set of parameters if the use of the first set of parameters results in a selected data bit rate, and outputting the second set of parameters as the first set of parameters.

14. The method of claim 13, wherein compressing the digital image information comprises:

converting the digital image information from spatial to frequency domain and generating transform coefficients;

quantizing the transform coefficients using first Q-steps; and

variable length coding the quantized transform coefficients.

15. The method of claim 14, wherein the first set of parameters includes the first Q-steps and adjusting the first set of parameters comprises:

adjusting the first Q-steps to generate the second set of parameters if the use of the first set of parameters results in the selected data bit rate, and outputting the second set of parameters as the first set of parameters.

16. The method of claim 14, wherein quantizing the transform coefficients using the first Q-steps and first frequency weight mask (FWM) tables.

17. The method of claim 16, wherein the first set of parameters includes the first Q-steps and the FWM tables, and wherein adjusting the first set of parameters comprises:

adjusting either one or both the first Q-steps and the first FWM tables to generate the second set of parameters if the use of the first set of parameters results in the selected data bit rate, and outputting the second set of parameters as the first set of parameters.

18. The method of claim 14, wherein converting the digital image information using ABSDCT based on a first ABSDCT threshold.

19. The method of claim 18, wherein the first set of parameters includes the first Q-steps and the first ABSDCT threshold, and wherein adjusting the first set of parameters comprises:

adjusting either one or both the first Q-steps and the first ABSDCT threshold to generate the second set of parameters if the use of the first set of parameters results in the selected data bit rate, and outputting the second set of parameters as the first set of parameters.

20. The method of claim 19, wherein variable length coding comprises Huffman coding the quantized transform coefficients using first Huffman code tables.

21. The method of claim 20, wherein the first set of parameters includes the first Q-steps and the first Huffman code tables, and wherein adjusting the first set of parameters comprises:

adjusting either one or both the first Q-steps and the first Huffman code tables to generate the second set of parameters if the use of the first set of parameters results in the selected data bit rate, and outputting the second set of parameters as the first set of parameters.

22. The method of claim 13, wherein adjusting the first set of parameters based on a statistical analysis to generate the second set of parameters.

23. The method of claim 22, wherein the adjusting the first set of parameters based on a bits per pixel analysis to determine if the use of the first set of parameters results in the selected data bit rate.

24. The method of claim 13, wherein the selected bit rate depends on either one of a maximum bit rate as allowed a limited bandwidth or an average bit rate over a certain time period.

25. An apparatus for encoding digital image information comprising:

means for outputting at least a first set of parameters; and

first means for compressing the digital image information using the first set of parameters.

26. The apparatus of claim 25, wherein the means for outputting at least the first set of parameters comprises:

second means for compressing the digital information using a second set of parameters;

means for outputting the second set of parameters;

means for adjusting the second set of parameters to generate a third set of parameters; and

means for outputting the third set of parameters as the second set of parameters, if the use of the second set of parameters results in a selected data bit rate, and otherwise, outputting the second set of parameters as the first set of parameters.

27. The apparatus of claim 25, wherein the means for outputting at least the first set of parameters comprises:

means for adjusting the first set of parameters to generate a second set of parameters if the use of the first set of parameters results in a selected data bit rate; and

means for outputting the second set of parameters as the first set of parameters.

28. An apparatus for encoding digital image information comprising:

a parameter generator to output at least a first set of parameters;

a first image compressor coupled to the parameter generator, the first image compressor to compress the digital image information using the first set of parameters.

29. The apparatus of claim 28, wherein the parameter generator comprises:

a second image compressor to compress the digital information using a second set of parameters;

a processor coupled to the first and second image compressors, the processor to output the second set of parameters, the processor to adjust the second set of parameters and output a third set of parameters as the second set of parameters, if the use of the second set of parameters results in a selected data bit rate, and otherwise, to output the second set of parameters as the first set of parameters.

30. The apparatus of claim 28, wherein the parameter generator comprises:

a processor to output the first set of parameters, the processor to adjust the first set of parameters to generate a second set of parameters if the use of the first set of parameters results in a selected data bit rate, and to output the second set of parameters as the first set of parameters.