Transform-Domain Operations for MPEG-2 to H.264 Transcoding
Date Issued
2005
Date
2005
Author(s)
Chen, Chen
DOI
en-US
Abstract
Usually, video signals are compressed before they are stored or transmitted over networks. In many applications, such as transcoding, manipulation of video signals directly on the compressed bit streams is more desirable than the approach where the compressed videos are fully decoded and then manipulated, because of the computational cost issue. For energy compaction purposes, video compression methods use techniques such as discrete cosine transform (DCT) to convert video signals from the pixel domain to the transform domain. Image operations such as motion compensation and down sampling have counterparts in the transform domain. The derivations of these transform-domain counterparts are based on the orthogonality of DCT and the linearity of these operations. However, since the data is organized block by block in the transform domain, the coding operations are not straightforward when applying to the transform-domain data. Therefore, there is a need to investigate the transform-domain operations, especially for H.264, which provides many advanced coding techniques.
The thesis investigates several coding operations, including transform kernel conversion, intra prediction and motion compensation for H.264. They are expected to have applications in the transform domain transcoder. In the context, we derive the transform-domain equivalent operations for these coding operations and provide the efficient way to implement the algorithm for each transform-domain operation. A transform-domain MPEG-2 to H.264 transcoder is devised, and its performance is evaluated and compared to the pixel domain approach.
In this thesis, we also formulate a general problem for rounding in the transform domain. The rounding operation is commonly performed in multimedia systems. Take half-pixel motion compensation as an example. The generation of new pixels at half-pixel locations requires a rounding operation for better approximation of the pixel values. However, rounding is a nonlinear operation; so its corresponding transform-domain operation does not exist. We propose an approximate solution to this problem and demonstrate that the proposed approach is better than other approaches when applied to an MPEG-2 decoder.
Subjects
MPEG-2
H.264
轉換域
轉換編碼
transform domain
transcoding
transcoder
Type
thesis
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