document: Optimization of requantization parameter for MPEG transcoding This paper considers transcoding in which an MPEG stream is converted to a low-bit-rate MPEG stream , and proposes a method in which the transcoding error can be reduced by optimally selecting the quantization parameter for each macroblock . In transcoding with a low compression ratio , it is crucial to prohibit transcoding with a requantization parameter which is 1 to 2 times the quantization parameter of the input stream . Consequently , as the first step , an optimization method for the requantization parameter is proposed which cares for the error propagation effect by interframe prediction . Then , the proposed optimization method is extended so that the method can also be applied to the case of a high compression ratio in which the rate-distortion curve is approximated for each macroblock in the range of requantization parameters larger than 2 times the quantization parameter . It is verified by a simulation experiment that the PSNR is improved by 0.5 to 0.8 dB compared to the case in which a 6 Mbit/s MPEG stream is not optimized by twofold recompression
doc_bio_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O B O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O B I O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O B I
extractive_keyphrases: transcoding error macroblock compression ratio error propagation effect interframe prediction psnr simulation twofold recompression
abstractive_keyphrases: requantization parameter optimization low-bit-rate mpeg stream rate-distortion curve rate conversion rate control 6 mbit/s