Rate-distortion Optimization Using Adaptive Lagrange Multipliers

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Abstract

In current standardized hybrid video encoders, the Lagrange multiplier determination model is a key component in rate-distortion optimization. This originated some 20 years ago based on an entropy-constrained high-rate approximation and experimental results obtained using an H.263 reference encoder on limited test material. In this paper, we present a comprehensive analysis of the results of a Lagrange multiplier selection experiment conducted on various video content using H.264/AVC and HEVC reference encoders. These results show that the original Lagrange multiplier selection methods, employed in both video encoders, are able to achieve optimum rate-distortion performance for I and P frames, but fail to perform well for B frames. The relationship is identified between the optimum Lagrange multipliers for B frames and distortion information obtained from the experimental results, leading to a novel Lagrange multiplier determination approach. The proposed method adaptively predicts the optimum Lagrange multiplier for B frames based on the distortion statistics of recent reconstructed frames. After integration into both H.264/AVC and HEVC reference encoders, this approach was evaluated on 36 test sequences with various resolutions and differing content types. The results show consistent bitrate savings for various hierarchical B frame configurations with minimal additional complexity. BD savings average approximately 3% when constant QP values are used for all frames, and 0.5% when non-zero QP offset values are employed for different B frame hierarchical levels.
Original languageEnglish
Number of pages11
JournalIEEE Transactions on Circuits and Systems for Video Technology
Early online date5 Oct 2018
DOIs
Publication statusE-pub ahead of print - 5 Oct 2018

Keywords

  • Video compression
  • rate-distortion optimization
  • Lagrange multiplier determination
  • H.264/AVC
  • HEVC

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