Release Notes for Version 2.4
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Release date — 22nd April, 2017.

Encoder enhancements
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1. HDR10+ supported. Dynamic metadata may be either supplied as a bitstream via the userSEI field of x265_picture, or as a json file that can be parsed by x265 and inserted into the bitstream; use —dhdr10-info to specify json file name, and —dhdr10-opt to enable optimization of inserting tone-map information only at IDR frames, or when the tone map information changes.
2. Lambda tables for 8, 10, and 12-bit encoding revised, resulting in significant enhancement to subjective visual quality.
3. Enhanced HDR10 encoding with HDR-specific QP optimizations for chroma, and luma planes of WCG content enabled; use —hdr-opt to activate.
4. Ability to accept analysis information from other previous encodes (that may or may not be x265), and selectively reuse and refine analysis for encoding subsequent passes enabled with the —refine-level option.
5. Slow and veryslow presets receive a 20% speed boost at iso-quality by enabling the —limit-tu option.
6. The bitrate target for x265 can now be dynamically reconfigured via the reconfigure API.
7. Performance optimized SAO algorithm introduced via the —limit-sao option; seeing 10% speed benefits at faster presets.

API changes
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1. x265_reconfigure API now also accepts rate-control parameters for dynamic reconfiguration.
2. Several additions to data fields in x265_analysis to support —refine-level: see x265.h for more details.

Bug fixes
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1. Avoid negative offsets in x265 lambda2 table with SAO enabled.
2. Fix mingw32 build error.
3. Seek now enabled for pipe input, in addition to file-based input
4. Fix issue of statically linking core-utils not working in linux.
5. Fix visual artifacts with —multi-pass-opt-distortion with VBV.
6. Fix bufferFill stats reported in csv.