Quantization/DCT Conversion Scheme for DCT-Domain MPEG-2 to H.264/AVC Transcoding

Joo-Kyong LEE
Ki-Dong CHUNG

Publication
IEICE TRANSACTIONS on Communications   Vol.E88-B    No.7    pp.2856-2863
Publication Date: 2005/07/01
Online ISSN: 
DOI: 10.1093/ietcom/e88-b.7.2856
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Mobile Multimedia Communications)
Category: 
Keyword: 
transcoder,  MPEG-2,  H.264/AVC,  DCT,  quantization,  

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Summary: 
The latest video coding standard, H.264/AVC, adopts 44 approximate transform instead of 88 discrete cosine transform (DCT) to avoid the inverse transform mismatch problem. However, that is only one of the factors that make it difficult to transcode pre-coded video contents with the previous standards to H.264/AVC in the common domain without causing cascaded pixel-domain transcoding. In this paper, to support the existent DCT-domain transcoding schemes and to reduce computational complexity, we propose an efficient algorithm that converts the quantized 88 DCT block into four newly quantized 44 transformed blocks. The experimental results show that the proposed scheme reduces computational complexity by 5-11% and improves video quality by 0.1-0.5 dB compared with the cascaded pixel-domain transcoding scheme that exploits inverse quantization (IQ), inverse DCT (IDCT), DCT, and re-quantization (re-Q).