Encoding apparatus and method
An encoding apparatus and method prevents image deterioration generated by repeatedly performing encoding and decoding by using a quantization matrix for quantization which is different from a quantization matrix for inverse quantization. In the encoding apparatus, a matrix selector selects a first quantization matrix in accordance with the complexity of an encoded picture pattern, and supplies a quantizer with information on the selected first quantization matrix. A matrix unit rewrites, by information on a second quantization matrix, the information described in an encoded stream output from a variable length code unit so that a quantization matrix to be used for inverse quantization is a second quantization matrix different from the first quantization matrix.
1. An encoding apparatus for encoding source video data, comprising:
discrete-cosine-transform means for outputting discrete-cosine-transform coefficients by implementing discrete-cosine-transform processing on the source video data;
quantization means for outputting quantized data by using a quantization matrix determined by a quantization index to quantize the discrete-cosine-transform coefficients;
a rate controller for determining complexity level of output encoded video data and generating a respective quantization index corresponding to said complexity level;
a matrix unit for rewriting said quantization matrix; and
encoding means for outputting an encoded stream by encoding the quantized data, together with information representing the rewritten quantization matrix;
wherein the quantization matrix used by said quantization means for quantization has quantization coefficients different from those in the rewritten quantization matrix used when inverse quantization in decoding is implemented.
2. An encoding method for encoding source video data, comprising the steps of:
outputting discrete-cosine-transform coefficients by implementing discrete-cosine-transform processing on the source video data;
outputting quantized data by using a first quantization matrix determined by a quantization index to quantize the discrete-cosine-transform coefficients;
determining complexity level of output encoded video data and generating a respective quantization index corresponding to said complexity level;
rewriting said first quantization matrix; and
outputting an encoded stream by encoding the quantized data, together with information representing the rewritten quantization matrix;
wherein the quantization matrix used for quantization has quantization coefficients different from those in the rewritten quantization matrix used when inverse quantization is implemented in decoding.