New architecture for dynamic frame-skipping transcoder

Kai Tat Fung, Yui Lam Chan, Wan Chi Siu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

80 Citations (Scopus)


Transcoding is a key technique for reducing the bitrate of a previously compressed video signal. A high transcoding ratio may result in an unacceptable picture quality when the full frame rate of the incoming video bitstream is used. Frame skipping is often used as an efficient scheme to allocate more bits to the representative frames, so that an acceptable quality for each frame can be maintained. However, the skipped frame must be decompressed completely, which might act as a reference frame to nonskipped frames for reconstruction. The newly quantized discrete cosine transform (DCT) coefficients of the prediction errors need to be re-computed for the nonskipped frame with reference to the previous nonskipped frame; this can create undesirable complexity as well as introduce re-encoding errors. In this paper, we propose new algorithms and a novel architecture for frame-rate reduction to improve picture quality and to reduce complexity. The proposed architecture is mainly performed on the DCT domain to achieve a transcoder with low complexity. With the direct addition of DCT coefficients and an error compensation feedback loop, re-encoding errors are reduced significantly. Furthermore, we propose a frame-rate control scheme which can dynamically adjust the number of skipped frames according to the incoming motion vectors and re-encoding errors due to transcoding such that the decoded sequence can have a smooth motion as well as better transcoded pictures. Experimental results show that, as compared to the conventional transcoder, the new architecture for frame-skipping transcoder is more robust, produces fewer requantization errors, and has reduced computational complexity.
Original languageEnglish
Pages (from-to)886-900
Number of pages15
JournalIEEE Transactions on Image Processing
Issue number8
Publication statusPublished - 1 Aug 2002


  • Compressed domain processing
  • DCT-based transcoder
  • Frame skipping
  • Rate control
  • Video transcoding

ASJC Scopus subject areas

  • Software
  • Computer Graphics and Computer-Aided Design


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