Release date - 26th December, 2016.
- Enhancements to TU selection algorithm with early-outs for improved speed; use
- New motion search method SEA (Successive Elimination Algorithm) supported now as :option: –me 4
- Bit-stream optimizations to improve fields in PPS and SPS for bit-rate savings through
- Enabled using VBV constraints when encoding without WPP.
- All param options dumped in SEI packet in bitstream when info selected.
- x265 now supports POWERPC-based systems. Several key functions also have optimized ALTIVEC kernels.
- Options to disable SEI and optional-VUI messages from bitstream made more descriptive.
- New option
--scenecut-biasto enable controlling bias to mark scene-cuts via cli.
- Support mono and mono16 color spaces for y4m input.
--min-cu-sizeof 64 no-longer supported for reasons of visual quality (was crashing earlier anyways.)
- API for CSV now expects version string for better integration of x265 into other applications.
Release date - 27th September, 2016
- Support for qg-size of 8
- Support for inserting non-IDR I-frames at scenecuts and when running with settings for fixed-GOP (min-keyint = max-keyint)
- Experimental support for slice-parallelism.
- Encode user-define SEI messages passed in through x265_picture object.
- Disable SEI and VUI messages from the bitstream
- Specify qpmin and qpmax
- Control number of bits to encode POC.
- QP fluctuation fix for first B-frame in mini-GOP for 2-pass encoding with tune-grain.
- Assembly fix for crashes in 32-bit from dct_sse4.
- Threadpool creation fix in windows platform.
Release date - 13th July, 2016
- uhd-bd: Enable Ultra-HD Bluray support
- rskip: Enables skipping recursion to analyze lower CU sizes using heuristics at different rd-levels. Provides good visual quality gains at the highest quality presets.
- rc-grain: Enables a new ratecontrol mode specifically for grainy content. Strictly prevents QP oscillations within and between frames to avoid grain fluctuations.
- tune grain: A fully refactored and improved option to encode film grain content including QP control as well as analysis options.
- asm: ARM assembly is now enabled by default, native or cross compiled builds supported on armv6 and later systems.
API and Key Behaviour Changes¶
- x265_rc_stats added to x265_picture, containing all RC decision points for that frame
- PTL: high tier is now allowed by default, chosen only if necessary
- multi-pass: First pass now uses slow-firstpass by default, enabling better RC decisions in future passes
- pools: fix behaviour on multi-socketed Windows systems, provide more flexibility in determining thread and pool counts
- ABR: improve bits allocation in the first few frames, abr reset, vbv and cutree improved
- An SSIM calculation bug was corrected
Release date - 29th January, 2016
- Quant offsets: This feature allows block level quantization offsets to be specified for every frame. An API-only feature.
- –intra-refresh: Keyframes can be replaced by a moving column of intra blocks in non-keyframes.
- –limit-modes: Intelligently restricts mode analysis.
- –max-luma and –min-luma for luma clipping, optional for HDR use-cases
- Emergency denoising is now enabled by default in very low bitrate, VBV encodes
- x265_frame_stats returns many additional fields: maxCLL, maxFALL, residual energy, scenecut and latency logging
- –qpfile now supports frametype ‘K”
- x265 now allows CRF ratecontrol in pass N (N greater than or equal to 2)
- Chroma subsampling format YUV 4:0:0 is now fully supported and tested
Presets and Performance¶
- Recently added features lookahead-slices, limit-modes, limit-refs have been enabled by default for applicable presets.
- The default psy-rd strength has been increased to 2.0
- Multi-socket machines now use a single pool of threads that can work cross-socket.
Release date - 10th August, 2015
- Experimental support for Main12 is now enabled. Partial assembly support exists.
- Main12 and Intra/Still picture profiles are now supported. Still picture profile is detected based on x265_param::totalFrames.
3. Three classes of encoding statistics are now available through the API. a) x265_stats - contains encoding statistics, available through x265_encoder_get_stats() b) x265_frame_stats and x265_cu_stats - contains frame encoding statistics, available through recon x265_picture 4. –csv a) x265_encoder_log() is now deprecated b) x265_param::csvfn is also deprecated 5. –log-level now controls only console logging, frame level console logging has been removed. 6. Support added for new color transfer characteristic ARIB STD-B67
- limit-refs: This feature limits the references analysed for individual CUS. Provides a nice tradeoff between efficiency and performance.
- aq-mode 3: A new aq-mode that provides additional biasing for low-light conditions.
- An improved scene cut detection logic that allows ratecontrol to manage visual quality at fade-ins and fade-outs better.
Preset and Tune Options¶
- tune grain: Increases psyRdoq strength to 10.0, and rdoq-level to 2.
- qg-size: Default value changed to 32.