HARMONIC QUANTIZER SCALE

• US 20120224627A1
• Filed: 05/10/2012
• Published: 09/06/2012
• Est. Priority Date: 05/05/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Srinivasan, Sridhar
• Granted Patent: US 8,588,298 B2
• Time in Patent Office: Days
• 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 that are simple fractions of each other; and

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

2. The method of claim 1 wherein the harmonic quantizer scale comprises a normal portion.

3. The method of claim 2 wherein the harmonic quantizer scale further comprises a denormal portion composed of a linear sequence of numbers.

4. The method of claim 2 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:

5. The method of claim 4 wherein the constant value c equals a power of 2.

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

7. The method of claim 4 wherein the constant value c is the number 32.

8. The method of claim 4, 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.

9. A computer-readable storage having instructions thereon for executing a method comprising:

receiving digital media data;

applying forward or reverse quantization to transform coefficients of the digital media data to quantized transform coefficients based on a quantization parameter chosen from a harmonic quantizer scale, wherein the quantization parameter is derived from an integer-valued index i, and a constant value c, as follows;

10. The method of claim 9 wherein the harmonic quantizer scale comprises a set of numbers related to each other via a simple fraction.

11. The method of claim 9 wherein the harmonic quantizer scale comprises a normal portion.

12. The method of claim 9 wherein the harmonic quantizer scale further comprises a denormal portion composed of a linear sequence of numbers.

13. The method of claim 9 wherein the constant value c equals a power of 2.

14. The method of claim 9 wherein the constant value c is the number 16.

15. The method of claim 9 wherein the constant value c is the number 32.

16. The method of claim 9, 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.

17. The method of claim 9, 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.

18. The method of claim 9, 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.

19. The method of claim 18, 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.

20. At least one program-storing device having program code 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;

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;

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;

QP_i=i for 1≦

i≦

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