Harmonic quantizer scale

• US 8,184,694 B2
• Filed: 02/16/2007
• Issued: 05/22/2012
• Est. Priority Date: 05/05/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Srinivasan, Sridhar
• Primary Examiner(s): Arani, Taghi
• Assistant Examiner(s): LEE, JASON T
• Application Number:
  US11/676,263
• Publication Number:
  US 20070258519A1
• Time in Patent Office: 1,922 Days
• Field of Search: 375/240.03, 375/240.04, 375/240.16
• US Class Current: 375/240.03
• 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 19/176 the region being a block, e.g. a macroblock
• 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

Abstract

A digital media encoder/decoder performs quantization/dequantization based on quantization parameters taken from a harmonic quantizer scale. The harmonic quantizer scale can include a normal portion consisting of quantization parameter values harmonically-related as simple fractions of each other, and a denormal portion of quantizers having a linear or other relation. The encoder/decoder further supports a scaled quantizer mode where quantization is performed based on the quantization parameter as scaled by a fractional value. A compressed domain contrast adjustment is effected by adjusting the quantization parameters in the compressed bitstream, without having to adjust and recode the digital media data in the compressed bitstream.

Claims

1. A method of coding/decoding digital media, comprising:

applying forward or reverse operations of a transform on blocks of digital media data;

applying forward or reverse quantization to transform coefficients of the digital media data based on a quantization parameter chosen from a harmonic quantizer scale, which includes a sequence of values in which successive values are related as simple fractions of each other;

performing coding or decoding of the quantized transform coefficients in a compressed bitstream; and

wherein the harmonic quantizer scale comprises a normal portion and a denormal portion, the denormal portion being composed of a linear sequence of numbers.

2. The method of claim 1 wherein the normal portion of the harmonic quantizer scale is defined by a rule, wherein the quantization parameter is derived from an integer-valued index i, and a constant value c, as follows:

3. The method of claim 2 wherein the constant value c equals a power of 2.

4. The method of claim 2 wherein the constant value c is the number 16.

5. The method of claim 2 wherein the constant value c is the number 32.

6. The method of claim 2, further comprising:

signaling at least one quantization parameter chosen from the harmonic quantizer scale in the compressed bitstream using a coded symbol for the integer-valued index i.

7. The method of claim 6, further comprising:

modifying the coded symbol of the integer-valued index i in the compressed bitstream to effect contrast adjustment of an image represented by the digital media data.

8. The method of claim 2, further comprising:

signaling a plurality of quantization parameters flexibly applied to separate partitions of the digital media data in the compressed bitstream using a sequence of coded symbols to define a table of quantization parameters represented via the rule by integer-valued indices i.

9. The method of claim 8, further comprising:

modifying the coded symbols in the table of quantization parameters in the compressed bitstream to effect contrast adjustment of an image represented by the digital media data.

10. The method of claim 1 wherein the harmonic quantizer scale is defined by a rule, wherein the quantization parameter is derived from an integer-valued index i, as follows:

11. The method of claim 1, further comprising:

signaling at least one quantization parameter chosen from the harmonic quantizer scale in the compressed bitstream as a quantization index that represents the value of the quantization parameter according to a harmonic quantizer scale rule.

12. The method of claim 1, further comprising:

signaling to use a scaled quantization mode or a non-scaled quantization mode in the compressed bitstream;

in the non-scaled quantization mode, performing said forward or reverse quantization of the transform coefficients using the quantization parameter without scaling; and

in the scaled quantization mode, performing said forward or reverse quantization of the transform coefficients using a scaled fraction of the quantization parameter.

13. The method of claim 1, further comprising:

modifying the quantization parameter to effect contrast adjustment of an image represented by the digital media data.

14. A digital media processing device comprising:

a memory for storing digital media data;

a digital media processor programmed to encode and/or decode the digital media data by applying forward or inverse operations of a transform to blocks of the digital media data, and performing quantization or dequantization of transform coefficients of the blocks based on at least one quantization parameter taken from a harmonic quantizer scale, which includes a sequence of values where successive values are related as simple fractions; and

wherein the harmonic quantizer scale comprises a normal portion and further comprises a denormal portion, which includes a linear sequence of numbers.

15. The digital media processing device of claim 14 wherein the harmonic quantizer scale is defined by a rule, wherein the quantization parameter is derived from an integer-valued index i, as follows:

16. At least one computer storage device having program code, which is not a signal, stored thereon for causing a digital media processing device to perform a method of decoding digital media data according to a codec, the method comprising:

decoding a quantizer symbol from a compressed bitstream representing a quantization parameter chosen from a harmonic quantizer scale for at least a portion of digital media data in the compressed bitstream, the harmonic quantizer scale including a sequence of values in which successive values are related as simple fractions of one another, the harmonic quantizer scale comprising a normal portion and a denormal portion having a linear sequence of numbers;

decoding transform coefficients of the digital media data portion in the compressed bitstream;

dequantizing the decoded transform coefficients based on the quantization parameter; and

performing an inverse transform to reconstruct digital media.

17. The at least one computer storage device of claim 16 wherein the quantizer symbol is an integer-valued index i that represents the quantization parameter according to a rule defining the harmonic quantizer scale as follows: