x265 2.3 Released

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By Pradeep Ramachandran

Version 2.3

Release date – 15th February, 2017.

Encoder enhancements

  1. New SSIM-based RD-cost computation for improved visual quality, and efficiency; use --ssim-rd to exercise.
  2. Multi-pass encoding can now share analysis information from prior passes (in addition to rate-control information) to improve performance and quality of subsequent passes; to your multi-pass command-lines that use the --pass option, add --multi-pass-opt-distortion to share distortion information, and --multi-pass-opt-analysis to share other analysis information.
  3. A dedicated thread pool for lookahead can now be specified with --lookahead-threads.
  4. option:–dynamic-rd dynamically increase analysis in areas where the bitrate is being capped by VBV; works for both CRF and ABR encodes with VBV settings.
  5. The number of bits used to signal the delta-QP can be optimized with the --opt-cu-delta-qpoption; found to be useful in some scenarios for lower bitrate targets.
  6. Experimental feature option:–aq-motion adds new QP offsets based on relative motion of a block with respect to the movement of the frame.

API changes

  1. Reconfigure API now supports signalling new scaling lists.
  2. x265 application’s csv functionality now reports time (in milliseconds) taken to encode each frame.
  3. --strict-cbrenables stricter bitrate adherence by adding filler bits when achieved bitrate is lower than the target; earlier, it was only reacting when the achieved rate was higher.
  4. --hdr can be used to ensure that max-cll and max-fall values are always signaled (even if 0,0).

Bug fixes

  1. Fixed incorrect HW thread counting on MacOS platform.
  2. Fixed scaling lists support for 4:4:4 videos.
  3. Inconsistent output fix for --opt-qp-pss by removing last slice’s QP from cost calculation.
  4. VTune profiling (enabled using ENABLE_VTUNE CMake option) now also works with 2017 VTune builds.