Rate adaptation transcoding for precoded video streams

  • Authors:

  • Zhijun Lei;Nicolas D. Georganas

  • Affiliations:

  • University of Ottawa;University of Ottawa

  • Venue:
  • Proceedings of the tenth ACM international conference on Multimedia
  • Year:
  • 2002

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Abstract

In order to transmit pre-encoded digital video over heterogeneous networks, it is necessary to employ transcoding techniques that convert pre-encoded video streams into streams having different bit rates and quality. The specified problem is referred to as rate shaping or rate adaptation. In this work, we propose a new rate control scheme for H.263+ based video transcoding. The proposed rate control scheme is comprised of Frame-Layer bit allocation and Macroblock-Layer rate control. At the frame layer, scene context statistics from the incoming video stream are utilized to detect scene changes and determine frame type. The bit budget is allocated to frames according to their energy and frame types. At the macroblock layer, a novel linear Rate-Quantization model is used for selecting quantization parameters for macroblocks. Implementation and experimental results show that the proposed algorithm can provide accurate bit allocation, and can effectively alleviate visual quality degradation after scene changes. This rate adaptation scheme can be used to provide flexible video bit rate adaptation for transmission of pre-encoded video over heterogeneous networks.