Block transform and quantization for image and video coding
First Claim
1. A method for decoding video or image information with a computing device that implements a video or image decoder, the method comprising:
- receiving quantized transform coefficients at the computing device;
with the computing device, de-quantizing the received quantized transform coefficients into de-quantized transform coefficients, wherein the de-quantizing scales the quantized transform coefficients by scaling factors selected from plural groups of scaling factors, wherein the quantized transform coefficients are logically organized in a block, wherein the inverse transform process is a two-dimensional inverse transform with row and column inverse transforms, the two-dimensional inverse transform having different norms, and wherein selection between the plural groups for the de-quantizing is based on relative coefficient position within the block; and
with the computing device, applying an inverse transform process to the de-quantized transform coefficients to generate reconstructed information therefrom.
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Abstract
An improved method and block transform for image or video encoding and decoding, wherein transformation and inverse transformation matrixes are defined such that computational complexity is significantly reduced when encoding and decoding. For example, in the two-dimensional inverse transformation of de-quantized transform coefficients into output pixel information during decoding, only four additions plus one shift operation are needed, per co-efficient transformation, all in sixteen-bit arithmetic. Transformations provide correct results because quantization during encoding and de-quantization (sixteen bit) during decoding, via the use of one of three tables selected based on each coefficient'"'"'s position, have parameter values that already compensate for factors of other transformation multiplications, except for those of a power of two, (e.g., two or one-half), which are performed by a shift operation during the transformation and inverse transformation processes. Computational complexity is significantly reduced with respect to other known transforms without adversely impacting compression or quality.
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Citations
23 Claims
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1. A method for decoding video or image information with a computing device that implements a video or image decoder, the method comprising:
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receiving quantized transform coefficients at the computing device; with the computing device, de-quantizing the received quantized transform coefficients into de-quantized transform coefficients, wherein the de-quantizing scales the quantized transform coefficients by scaling factors selected from plural groups of scaling factors, wherein the quantized transform coefficients are logically organized in a block, wherein the inverse transform process is a two-dimensional inverse transform with row and column inverse transforms, the two-dimensional inverse transform having different norms, and wherein selection between the plural groups for the de-quantizing is based on relative coefficient position within the block; and with the computing device, applying an inverse transform process to the de-quantized transform coefficients to generate reconstructed information therefrom. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of coding video or image information in a computing device that implements a video or image encoder, the method comprising:
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with the computing device, applying a transform process to the information to produce transform coefficients; and with the computing device, quantizing the transform coefficients into quantized transform coefficients, wherein the quantizing scales the transform coefficients by scaling factors selected from plural groups of scaling factors, wherein the transform coefficients are logically organized in a block, wherein the transform process is a two-dimensional transform with row and column transforms, the two-dimensional transform having different norms, wherein scaling factors are selected from the plural groups of scaling factors depending on a group index that identifies the selected group and a quantization parameter index selecting the scaling factor within the selected group, and wherein selection between the plural groups for the quantizing is based on relative coefficient position within the block. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A video decoder comprising:
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means for de-quantizing quantized transform coefficients into de-quantized transform coefficients, wherein the de-quantizing scales the quantized transform coefficients by scaling factors selected from three groups of scaling factors, wherein the de-quantizing includes multiplying each of the quantized transform coefficients by one of the scaling factors, wherein the quantized transform coefficients are logically organized in a 4×
4 block, wherein the inverse transform process is a two-dimensional inverse transform with row and column inverse transforms, the two-dimensional inverse transform having different norms, wherein scaling factors are selected from the plural groups of scaling factors depending on a group index that identifies the selected group and a quantization parameter index selecting the scaling factor within the selected group, and wherein selection between the three groups is based on relative coefficient position within the block; andmeans for applying an inverse transform process to the de-quantized transform coefficients. - View Dependent Claims (20, 21, 22, 23)
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Specification