Adaptive multiple quantization

• US 20050036699A1
• Filed: 07/17/2004
• Published: 02/17/2005
• Est. Priority Date: 07/18/2003
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Lin, Chih-Lung, Srinivasan, Sridhar, Hsu, Pohsiang, Holcomb, Thomas W.
• Granted Patent: US 7,580,584 B2
• Time in Patent Office: Days
• US Class Current: 382/239
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/136 Incoming video signal characteristics or properties
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• 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 19/18 the unit being a set of transform coefficients
• 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 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards

Abstract

With adaptive multiple quantization, a video or other digital media codec can adaptively select among multiple quantizers to apply to transform coefficients based on content or bit rate constraints, so as to improve quality through rate-distortion optimization. The switch in quantizers can be signaled at the sequence level or frame level of the bitstream syntax, or can be implicitly specified in the syntax.

Claims

1. A method of coding/decoding video, comprising:

adaptively selecting among multiple quantizer modes based at least in part on bit rate constraints for coding a picture in a video sequence; and

quantizing transform coefficients for blocks of the picture using the quantizer mode.

2. The method of claim 1 wherein the multiple quantizer modes comprise a uniform quantizer and a non-uniform quantizer.

3. The method of claim 1 wherein the multiple quantizer modes comprise quantizers having differing dead zone widths.

4. The method of claim 1 further comprising:

explicitly signaling the adaptively selected quantizer mode of the picture at any of a sequence level or frame level of a bit stream syntax.

5. The method of claim 1 further comprising:

implicitly signaling the adaptively selected quantizer mode of the picture at a frame level by a value of a syntax element representing a quantizer scale.

6. The method of claim 5 wherein the syntax element is a quantizer index, the quantizer index having a discontinuous relationship to the quantizer scale coincident with implicitly signaling a switch in quantizer mode for more smoothly representing quality.

7. The method of decoding a compressed video sequence using adaptive multiple quantization, the method comprising:

decoding syntax elements from the compressed video sequence indicating which of multiple quantizers to use on individual pictures of the compressed video sequence; and

inverse quantizing quantized transform coefficients of the individual pictures using the respective quantizer indicated by the decoded syntax elements to use on the individual pictures.

8. The method of claim 7 wherein the syntax elements comprise a quantizer specifier element signaled at a sequence level of a bit stream syntax, the quantizer specifier having values indicating which of the multiple quantizers to use on all pictures of the compressed video sequence.

9. The method of claim 7 wherein the syntax elements comprise a quantizer specifier element signaled at a sequence level of a bit stream syntax, the quantizer specifier having values indicating whether the quantizer is implicitly or explicitly signaled at a frame level of the bit stream syntax.

10. The method of claim 7 wherein the syntax elements comprise a quantizer specifier element signaled at a sequence level of a bit stream syntax, the quantizer specifier having values indicating the quantizer is signaled at a frame level of the bit stream syntax, or one of the multiple quantizers to use on all pictures of the compressed video sequence.

11. The method of claim 7 wherein the syntax elements comprise a quantizer index element signaled at a frame level, the quantizer index element specifying a quantizer scale of a quantizer to use on an individual picture of the compressed video sequence, the quantizer index element further implicitly representing which of multiple quantizers to use on the picture.

12. The method of claim 7 wherein the quantizer index element has a discontinuous relationship to the quantizer scale coincident with implicitly signaling a switch in quantizer mode for more smoothly representing quality.

13. A computer-readable medium storing computer-executable instructions for causing a computer system programmed thereby to perform a method comprising:

decoding syntax elements from the compressed video sequence indicating which of multiple quantizers to use on individual pictures of the compressed video sequence; and

inverse quantizing quantized transform coefficients of the individual pictures using the respective quantizer indicated by the decoded syntax elements to use on the individual pictures.

14. The computer-readable medium of claim 13 wherein the syntax elements comprise a quantizer specifier element signaled at a sequence level of a bit stream syntax, the quantizer specifier having values indicating which of the multiple quantizers to use on all pictures of the compressed video sequence.

15. The computer-readable medium of claim 13 wherein the syntax elements comprise a quantizer specifier element signaled at a sequence level of a bit stream syntax, the quantizer specifier having values indicating whether the quantizer is implicitly or explicitly signaled at a frame level of the bit stream syntax.

16. The computer-readable medium of claim 13 wherein the syntax elements comprise a quantizer specifier element signaled at a sequence level of a bit stream syntax, the quantizer specifier having values indicating the quantizer is signaled at a frame level of the bit stream syntax, or one of the multiple quantizers to use on all pictures of the compressed video sequence.

17. The computer-readable medium of claim 13 wherein the syntax elements comprise a quantizer index element signaled at a frame level, the quantizer index element specifying a quantizer scale of a quantizer to use on an individual picture of the compressed video sequence, the quantizer index element further implicitly representing which of multiple quantizers to use on the picture.

18. The computer-readable medium of claim 13 wherein the quantizer index element has a discontinuous relationship to the quantizer scale coincident with implicitly signaling a switch in quantizer mode for more smoothly representing quality.