Leveraging the quantization offset for improved requantization transcoding of H.264/AVC video

  • Authors:

  • Stijn Notebaert;Jan De Cock;Kenneth Vermeirsch;Peter Lambert;Rik Van de Walle

  • Affiliations:

  • Multimedia Lab, Department of Electronics and Information Systems, IBBT, Ghent University, Ghent-Ledeberg, Belgium;Multimedia Lab, Department of Electronics and Information Systems, IBBT, Ghent University, Ghent-Ledeberg, Belgium;Multimedia Lab, Department of Electronics and Information Systems, IBBT, Ghent University, Ghent-Ledeberg, Belgium;Multimedia Lab, Department of Electronics and Information Systems, IBBT, Ghent University, Ghent-Ledeberg, Belgium;Department of Electronics and Information Systems - Multimedia Lab, Ghent University, Gaston Crommenlaan, Ledeberg-Ghent, Belgium

  • Venue:
  • PCS'09 Proceedings of the 27th conference on Picture Coding Symposium
  • Year:
  • 2009

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Abstract

Requantization transcoding is a method for reducing the bit rate of compressed video bitstreams. Most research on requantization is concerned with the architectural design, the selection of a suitable quantizer, or the reduction of requantization errors. In this paper, we propose to incorporate a new dimension in requantization transcoding: the quantization offset. We compare two requantization methods: increasing the quantization step size and decreasing the quantization offset. Furthermore, we propose a novel heuristic for requantization transcoding based on a theoretical rate-distortion analysis. The experimental results for H.264/AVC video show that requantization is improved in rate-distortion sense with gains up to 1 dB for open-loop requantization of B pictures compared to requantization with fixed quantization offset.