PolyU Institutional Repository >
Electronic and Information Engineering >
EIE Journal/Magazine Articles >
Please use this identifier to cite or link to this item:
|Title: ||On transcoding a B-frame to a P-frame in the compressed domain|
|Authors: ||Siu, Wan-chi|
|Subjects: ||B-picture and P-picture|
Compressed domain processing
Video coding and transcoding
|Issue Date: ||Oct-2007 |
|Citation: ||IEEE Transactions on multimedia, Oct. 2007, v. 9, no. 6, p.1093-1102.|
|Abstract: ||Only a limited number of methods have been proposed to realize heterogeneous transcoding, for example from MPEG-2 to H.263, or from H.264 to H.263. The major difficulties of transcoding a B-picture to a P-picture are that the incoming discrete cosine transform (DCT) coefficients of the B-frame are prediction errors arising from both forward and backward predictions,
whilst the prediction errors in the DCT domain arising from the prediction using the previous frame alone are not available.
The required new prediction errors need to be re-estimated in the pixel domain. This process involves highly complex computation
and introduces re-encoding errors. We propose a new approach to convert a B-picture into a P-picture by making use
of some properties of motion compensation in the DCT domain and the direct addition of DCT coefficients. We derive a set of
equations and formulate the problem of how to obtain the DCT coefficients. One difficulty is that the last P-frame inside a GOP with an IBBP structure, for example, needs to be transcoded to become the last P-frame in the IPPP structure, and it has to be linked to the previous reconstructed P-frame instead of to the I-frame. We increased the speed of the transcoding process by making use of the motion activity which is expressed in terms of
the correlation between pictures. The whole transcoding process is done in the transform domain, hence re-encoding errors are completely avoided. Results from our experimental work show that the proposed video transcoder not only achieves a speed-up of two to six times that of the conventional video transcoder, but it also substantially improves the quality of the video.|
|Rights: ||© 2007 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.|
This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.
|Type: ||Journal/Magazine Article|
|Appears in Collections:||EIE Journal/Magazine Articles|
All items in the PolyU Institutional Repository are protected by copyright, with all rights reserved, unless otherwise indicated.
No item in the PolyU IR may be reproduced for commercial or resale purposes.