Release v3.6.0 Helia

2023-02-03 v3.6.0
  This release includes compression efficiency and perceptual quality
  improvements, speedup and memory optimizations, and some new features.
  This release is ABI compatible with the last release.

  - New Features
    * New values 20-27 (corresponding to levels 7.0-7.3 and 8.0-8.3) for
      the encoder control AV1E_SET_TARGET_SEQ_LEVEL_IDX (note that the
      proposal to add the new levels are still in draft status). The
      original special value 24 (keep level stats only for level
      monitoring) is renumbered as 32.
    * New encoder control AV1E_SET_SKIP_POSTPROC_FILTERING to skip the
      application of post-processing filters on reconstructed frame in
      all intra mode.
    * New encoder option "kf-max-pyr-height": Maximum height of pyramid
      structure used for the GOP starting with a key frame (-1 to 5).
    * Make SVC work for screen content.
    * Rate control improvements to reduce frame-size spikes for screen
      content coding.
    * RISC-V architecture support with gcc toolchain.

  - Compression Efficiency Improvements
    * Peak compression efficiency in VOD setting is improved by 1%.
    * 0.7% - 2.2% RTC encoding BDrate gains for real time speed 8 to 10.
    * 15% RTC encoding BDrate gains for screen content speed 10.

  - Perceptual Quality Improvements
    * Resolved a visual quality issue that was reported for high
      resolution clips (2K) for speed 4 and above in VOD use case.
    * Visual quality improvements to screen content coding.
    * Quality improvements to temporal layer RTC coding.

  - Speedup and Memory Optimizations
    * RTC single-thread encoder speedup:
      o ~6% instruction count reduction for speed 5 and 6.
      o ~15% instruction count reduction for speed 7.
      o ~10% instruction count reduction for speed 8 to 10 (>=360p
    * RTC multi-thread encoder speedup (beyond single-thread speedup):
      o 5-8% encode time reduction for speed 7 to 10.
    * RTC screen-content encoder speedup:
      o 11% instruction count reduction for speed 9 and 10 (>=720p
    * ~5% reduction in heap memory requirements for RTC, speed 6 to 10.
    * AVIF:
      o 4-5% speedup for speed 9 in still-picture encoding mode.
      o 3-4% heap memory reduction in still-picture encoding mode for
        360p-720p resolutions with multiple threads.

  - Bug Fixes
    * Added a workaround for an AV1 specification bug which makes
      TRANSLATION type global motion models unusable.
    * Fixed AddressSanitizer global-buffer-overflow errors in
    * Fixed AddressSanitizer heap-buffer-overflow error in
    * chromium:1393384 Avoid scene detection on spatial resize.
    * aomedia:3308 Remove color artifacts under high motion.
    * aomedia:3310 Avoid out of memory failures with Visual Studio 2017,
      2019, and 2022 for Win32 x86 builds.
    * aomedia:3346 Make SVC work properly for screen content.
    * aomedia:3348 Fix a bug where an uninitialized search_site is used.
    * aomedia:3365 Work around what seems like a Visual Studio 2022
      compiler optimization bug.
    * aomedia:3369 Incorrect PSNR values reported by libaom for 12-bit