Encoding rate conversion device, encoding rate conversion method, and integrated circuit

Abstract

A plurality of macro-blocks constituting encoding data is inverse-quantized by using a first quantization matrix used for the encoding of a picture to acquire a plurality of pieces of coefficient data. The first quantization matrix is converted into a second quantization matrix by using a first conversion value for converting the value of the low-frequency coefficient corresponding to a frequency lower than a predetermined frequency and a second conversion value which is a value for converting the value of a high-frequency coefficient and larger than the first conversion value out of the coefficients indicated by the first quantization matrix (S408). If the second quantization matrix is a matrix for increasing the encoding rate of the encoding data, the converted scale value after the value of quantization scale corresponding to at least one macro-block is multiplied by beta1(>=1) is calculated. At least a part of the plurality of pieces of coefficient data is quantized by using the second quantization matrix and the calculated converted scale value corresponding to the macro-block corresponding to the at least part of coefficient data.

Description

technical field [0001] The present invention relates to a technique for converting a coding rate in order to further reduce the amount of information of coded data, and more specifically, to a coding rate converting device and the like for suppressing image quality deterioration accompanying the coding rate conversion. Background technique [0002] In recent years, MPEG2 (Moving Picture Experts Group 2: Moving Picture Experts Group 2) for realizing high compression is used as an image coding technique. This technology is used in recording media such as digital broadcasting, DVD, and the Internet, and in combination with these applications, the bit rate (bitrate) can be selected within a certain range. [0003] For example, when selecting a bit rate for recording a high-quality digital broadcast on a recording medium, instead of recording the high-quality data on the recording medium as it is, the encoding rate is converted so that the bit rate Reduced so that more data can ...

AI Technical Summary

Problems solved by technology

[0126] In other words, in the above-mentioned integrated coding rate conversion device 13000, it is impossible to realize the coding rate conversion that can suppress the deterioration of the image quality due to the quantization error of the low-frequency component of the DCT coefficients of the entire MB, while improving the fineness. In specific MBs such as high MBs, image quality degradation due to not only low-frequency components but also quantization errors in high-frequency components of DCT coefficients is suppressed

[0127] In addition, the above description was based on MPEG2, but the same problem also exists in the following image codec, that is, the image codec that performs encoding based on DCT transform or orthogonal transform based on DCT transform specifies the quantization matrix An image codec that specifies the quantization scale as a macroblock unit for a picture unit

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