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Optimisation of a quantisation matrix for image and video coding

A technology of quantization matrix and image sequence, applied in the field of quantization matrix, it can solve the problem that the method is not optimal

Inactive Publication Date: 2006-06-28
THOMSON LICENSING SA
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Problems solved by technology

However, these perceptually optimal methods are not optimal for high bitrate encoding

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  • Optimisation of a quantisation matrix for image and video coding
  • Optimisation of a quantisation matrix for image and video coding
  • Optimisation of a quantisation matrix for image and video coding

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[0066] Several adaptive calculation methods of quantization matrices for both intra blocks and inter blocks will be described below. These methods can be used in all discrete cosine transform (DCT) based image or video coding standards, such as JPEG, MPEG-2 and MPEG-4 H.264 FRExt, and provide flexibility to the quantization process to improve subjective or objective quality, and even adjust the bit rate. For high definition (HD) video coding, 8*8 resizing performs better than 4*4 resizing. Therefore, in the following description, for intra blocks and inter blocks, 4*4 transformation is disabled, and quantization matrices both have a size of 8*8, if not stated otherwise.

[0067] figure 1 The average distribution of the amplitude levels (ie histogram) of the 64 DCT coefficients of all intra-frame 8*8 blocks in the HDTV sequence Kung_fu is shown. Each small image corresponds to the DCT position. The horizontal coordinate is the quantized amplitude (level), and the vertical c...

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Abstract

Disclosed is a method and apparatus for generating a quantization matrix for encoding an image or image sequence, wherein the effect of greatly reducing the data rate in video encoding is achieved by quantizing the transformed frequency coefficients or components of a pixel block, so that only Fewer amplitude levels are encoded, and a portion of quantized amplitudes becomes 0 and does not need to be encoded as quantized amplitudes. The quantization matrix generation of the present invention starts with a default quantization matrix and thus results in the perceptually optimal quantization matrix for a given sequence of images. In the first pass, candidate quantization matrices are iteratively constructed for a given sequence of images by simultaneously increasing the scaling values ​​for some coefficient positions and decreasing the scaling values ​​for some other coefficient positions. In the second pass, the resulting quantization matrix is ​​applied to the image sequence for re-encoding.

Description

technical field [0001] The invention relates to a method and a device for adaptively generating quantization matrices usable for encoding an image or image sequence. Background technique [0002] A significant data rate reduction effect in video coding can be achieved by quantizing the (transformed) frequency coefficients or components of a pixel block, so that thereafter only fewer amplitude levels need to be encoded, and a part of the quantized amplitude becomes 0 and does not need to be encoded as a quantized magnitude. Many transform-based video coding standards use default quantization matrices to achieve better subjective video coding / decoding quality, such as ISO / IEC (International Organization for Standardization / International Electrotechnical Commission) 13818-2 (MPEG-2 Video). The 'quantization matrix' assigns smaller scaling values ​​(i.e. with larger divisors) to certain frequencies of the block if the associated horizontal and / or vertical frequencies are consid...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04N7/26
CPCH04N19/172H04N19/134H04N19/61H04N19/60H04N19/126H04N19/154H04N19/177H04N19/174H04N19/192H04N19/124
Inventor 陈颖翟杰夫
Owner THOMSON LICENSING SA
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