[x265] [ANN] x265 version 2.8 released

Ashok Kumar Mishra ashok at multicorewareinc.com
Mon May 21 12:21:57 CEST 2018

 Hi all,

x265 version 2.8 is now out! The key new improvements include support for
AVX-512 assembly, VMAF for objective quality measurement of a video
sequence and dynamic refinement for switching between different inter
refine levels.
The tarball of this release can be downloaded from <

Release date - 21/05/2018

Version 2.8

New features
1. :option:`--asm avx512` used to enable AVX-512 in x265. Default disabled.
    For 4K main10 high-quality encoding, we are seeing good gains; for
other resolutions and presets, we don't recommend using this setting for

2. :option:`--dynamic-refine` dynamically switches between different inter
refine levels. Default disabled.
    It is recommended to use :option:`--refine-intra 4' with dynamic
refinement for a better trade-off between encode efficiency and performance
than using static refinement.

3. :option:`--single-sei`
    Encode SEI messages in a single NAL unit instead of multiple NAL units.
Default disabled.

4. :option:`--max-ausize-factor` controls the maximum AU size defined in
HEVC specification.
    It represents the percentage of maximum AU size used. Default is 1.

5. VMAF (Video Multi-Method Assessment Fusion)
   Added VMAF support for objective quality measurement of a video
   Enable cmake option ENABLE_LIBVMAF to report per frame and aggregate
VMAF score. The frame level VMAF score does not include temporal scores.
   This is supported only on linux for now.

Encoder enhancements
1. Introduced refine-intra level 4 to improve quality.
2. Support for HLG-graded content and pic_struct in SEI message.

Bug Fixes
1. Fix 32 bit build error (using CMAKE GUI) in Linux.
2. Fix 32 bit build error for asm primitives.
3. Fix build error on mac OS.
4. Fix VBV lookahead in analysis load to achieve target bit-rate.

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