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Requantization transcoding for H.264/AVC video coding / Jan De Cock in Signal processing. Image communication, Vol. 25 N° 4 (Avril 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 4 (Avril 2010) . - pp. 235–254 Titre : Requantization transcoding for H.264/AVC video coding Type de document : texte imprimé Auteurs : Jan De Cock, Auteur ; Stijn Notebaert, Auteur ; Peter Lambert, Auteur Année de publication : 2012 Article en page(s) : pp. 235–254 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Transcoding  Requantization  H.264/AVC  Drift  propagation  Drift  compensation Résumé : In this paper, efficient solutions for requantization transcoding in H.264/AVC are presented. By requantizing residual coefficients in the bitstream, different error components can appear in the transcoded video stream. Firstly, a requantization error is present due to successive quantization in encoder and transcoder. In addition to the requantization error, the loss of information caused by coarser quantization will propagate due to dependencies in the bitstream. Because of the use of intra prediction and motion-compensated prediction in H.264/AVC, both spatial and temporal drift propagation arise in transcoded H.264/AVC video streams. The spatial drift in intra-predicted blocks results from mismatches in the surrounding prediction pixels as a consequence of requantization. In this paper, both spatial and temporal drift components are analyzed. As is shown, spatial drift has a determining impact on the visual quality of transcoded video streams in H.264/AVC. In particular, this type of drift results in serious distortion and disturbing artifacts in the transcoded video stream. In order to avoid the spatially propagating distortion, we introduce transcoding architectures based on spatial compensation techniques. By combining the individual temporal and spatial compensation approaches and applying different techniques based on the picture and/or macroblock type, overall architectures are obtained that provide a trade-off between computational complexity and rate-distortion performance. The complexity of the presented architectures is significantly reduced when compared to cascaded decoder–encoder solutions, which are typically used for H.264/AVC transcoding. The reduction in complexity is particularly large for the solution which uses spatial compensation only. When compared to traditional solutions without spatial compensation, both visual and objective quality results are highly improved. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S092359651000007X [article] Requantization transcoding for H.264/AVC video coding [texte imprimé] / Jan De Cock, Auteur ; Stijn Notebaert, Auteur ; Peter Lambert, Auteur . - 2012 . - pp. 235–254. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 4 (Avril 2010) . - pp. 235–254 Mots-clés : Transcoding  Requantization  H.264/AVC  Drift  propagation  Drift  compensation Résumé : In this paper, efficient solutions for requantization transcoding in H.264/AVC are presented. By requantizing residual coefficients in the bitstream, different error components can appear in the transcoded video stream. Firstly, a requantization error is present due to successive quantization in encoder and transcoder. In addition to the requantization error, the loss of information caused by coarser quantization will propagate due to dependencies in the bitstream. Because of the use of intra prediction and motion-compensated prediction in H.264/AVC, both spatial and temporal drift propagation arise in transcoded H.264/AVC video streams. The spatial drift in intra-predicted blocks results from mismatches in the surrounding prediction pixels as a consequence of requantization. In this paper, both spatial and temporal drift components are analyzed. As is shown, spatial drift has a determining impact on the visual quality of transcoded video streams in H.264/AVC. In particular, this type of drift results in serious distortion and disturbing artifacts in the transcoded video stream. In order to avoid the spatially propagating distortion, we introduce transcoding architectures based on spatial compensation techniques. By combining the individual temporal and spatial compensation approaches and applying different techniques based on the picture and/or macroblock type, overall architectures are obtained that provide a trade-off between computational complexity and rate-distortion performance. The complexity of the presented architectures is significantly reduced when compared to cascaded decoder–encoder solutions, which are typically used for H.264/AVC transcoding. The reduction in complexity is particularly large for the solution which uses spatial compensation only. When compared to traditional solutions without spatial compensation, both visual and objective quality results are highly improved. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S092359651000007X