x265 v2.0 released

By Pradeep Ramachandran

x265 version 2.0 has been released. This release supports many new features as well as support for ARM assembly optimizations for most basic pixel and ME operations, as well as SAO cleanups and a fully tested reconfigure functionality.

Full documentation is available at http://x265.readthedocs.org/en/stable/

=========================================== New Features =========================================

• 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
=============================================== Misc ==============================================
• An SSIM calculation bug was corrected

x265 version 1.9

By By Pradeep Ramachandran

x265 version 1.9 has now been released. This release supports many new features as well as additional assembly optimizations for Main12, intra prediction and SAO. Recently added features lookahead-slices, limit-refs and limit-modes have been enabled by default in the supported presets. Full documentation is available at http://x265.readthedocs.org

New Features

  • 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 API Changes – 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.

Performance Presets

By Tom Vaughan

x265 has ten performance presets which enable anyone to make a good choice between encoding speed and compression efficiency.  These presets are combinations of x265 settings that should provide the best possible result at the encoding speed that you want to achieve.

If you want the highest compression efficiency (quality at your desired bit rate), you can select “–preset veryslow”.  Of course, “–preset veryslow” will run much slower than one of the faster x265 presets, so you will either need more time or more compute power (a more powerful PC or server).  If you’re trying to encode in real time, you will need x265 to maintain an encoding speed that is faster than the frame rate of your video, and so you’ll want to choose one of the faster presets, like “–preset faster” or “–preset veryfast”.

Over the past year we’ve added a number of new capabilities to x265 designed to allow it to run faster with very little tradeoff in encoding efficiency.  These include –limit-refs, –limit-modes, and –lookahead-slices.  We’ve performed extensive testing using a set of videos at various sizes (720P, 1080P and 2160P) on a range of machines.  We tested many possible improvements to our performance presets, trying to find the right combination of settings at each performance level.  The result is an update to our performance presets that incorporates some of our new algorithms, and a few changes to some of the existing settings.  The following charts illustrate the benefits of the new presets.  Your mileage may vary depending on your machine and your content.  In some cases you’ll notice a big improvement in speed, with a small tradeoff in quality, and in other cases you’ll notice both improved quality and speed.

The data points below show the average encoding speed and efficiency relative to the old (v1.8) veryslow preset.





HEVC Advance Reduces Proposed License Fees

By Tom Vaughan

The patent licensing organization known as HEVC Advance has announced a revision to the royalty rates they propose to charge companies who sell hardware, software and content that utilizes the HEVC standard.

Our opinion:  While these rates are a good step in the right direction, they are still many times higher than what licensees paid for H.264 for the past decade, and they would have to be paid in addition to the  MPEG-LA HEVC license fees (20 cents per unit after the first 100,000 units in each year with a $25 million annual cap, no content royalties).  We are optimistic that large licensees including Intel, Samsung, Apple, Microsoft, Google, movie studios and all of the many TV, mobile and PC device OEMs will convince the companies involved with HEVC Advance to join the MPEG-LA licensees, enabling licensing at reasonable rates from a single license pool.

Royalty rates for 4K TVs are now proposed to be $1.20 per unit, plus up to 75 cents per unit if HEVC profile extensions are supported.  PCs and set-top boxes would be liable for 80 cents per unit, and mobile devices would cost 40 cents per unit.  Companies such as Apple and Amazon which offer both mobile and connected home devices would be liable for up to $40 million in device royalties per year, in addition to their MPEG-LA HEVC license which will cost up to $25 million per year.

Whereas they had previously announced that all companies distributing HEVC content would have to pay a royalty of 0.5% of their top-line revenue attributable to HEVC, without any annual cap, they have revised their proposed content royalty to charge only for subscription-based services and for content for sale on a per-title basis (including streaming content and physical media, such as Blu-ray discs).  Content fees will start at 0.5 cents per subscriber per month, rising to 2.5 cents per subscriber per month in 2020.  Per-title fees are 2.5 cents.  In either category, there is a $2.5 million annual royalty cap, with a $5 million cap for companies who distribute content through all three content categories.  Services that do not charge for content, including ad-supported services such as YouTube and Facebook would not be charged an HEVC content royalty.

HEVC Advance Content Royalties