Zhengrong Wang

US Patent:

60496304, Apr 11, 2000

Filed:

Oct 27, 1997

Appl. No.:

8/962927

Inventors:

Zhengrong Wang - Santa Ana CA
Paul Steven Houle - Costa Mesa CA

Assignee:

America Online, Inc. - CA

International Classification:

G06T 900

US Classification:

382239

Abstract:

A method and apparatus for adaptive bit allocation and hybrid lossless entropy encoding in a lossy compression system. The invention includes three components: (1) a transform stage to decorrelate image data into a baseband and multiple subbands, (2) a quantization stage to quantize the resulting transform coefficients, and (3) a lossless entropy coder stage to encode the quantized indexes. In the preferred embodiment, the transform stage uses a wavelet transform algorithm. The quantization stage adaptively estimates values for parameters defining an approximation between quantization size and the logarithm of quantization error, and recursively calculates the optimal quantization size for each band to achieve a desired bit rate. The baseband and subbands are transformed into quantization matrices using the corresponding quantization sizes. The lossless entropy coder stage uses the observation that the entropy property of run lengths of zero index values in the subband quantization matrices is different from the entropy property of non-zero indices.

US Patent:

56821522, Oct 28, 1997

Filed:

Mar 19, 1996

Appl. No.:

8/618368

Inventors:

Zhengrong Wang - Santa Ana CA
Paul Steven Houle - Costa Mesa CA

Assignee:

Johnson-Grace Company - Newport Beach CA

International Classification:

H04N 700
H04N 750

US Classification:

341 50

Abstract:

A method and apparatus for adaptive bit allocation and hybrid lossless entropy encoding in a lossy compression system. The invention includes three components: (1) a transform stage to decorrelate image data into a baseband and multiple subbands, (2) a quantization stage to quantize the resulting transform coefficients, and (3) a lossless entropy coder stage to encode the quantized indexes. In the preferred embodiment, the transform stage uses a wavelet transform algorithm. The quantization stage adaptively estimates values for parameters defining an approximation between quantization size and the logarithm of quantization error, and recursively calculates the optimal quantization size for each band to achieve a desired bit rate. The baseband and subbands are transformed into quantization matrices using the corresponding quantization sizes. The lossless entropy coder stage uses the observation that the entropy property of run lengths of zero index values in the subband quantization matrices is different from the entropy property of non-zero indices.