libaom v3.8.0 release candidate 1

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Wan-Teh Chang

Dec 1, 2023, 6:35:49 PM12/1/23
Hi everyone,

libaom v3.8.0 release candidate 1 is tagged with v3.8.0-rc1. Your
testing is greatly appreciated.

Release Notes:

This release includes new codec interfaces, compression efficiency and
perceptual improvements, speedup and memory optimizations and many bug
fixes. This release is ABI compatible with the last release.

- New Features
* New codec controls:
* AV1E_SET_MAX_CONSEC_FRAME_DROP_CBR: Set the maximum number of
consecutive frame drops allowed for the frame dropper in 1 pass
CBR mode.
* Run-time CPU feature detection for all Arm platforms:
CRC, DotProd, I8MM and SVE CPU feature presence is detected at run
time and code paths making use of these features are selected
dynamically. These code paths provide meaningful performance gains
for standard bitdepth RTC and VoD encoding: up to 10% and 20%
respectively, over the Armv8.0-A baseline build.
* RTC: Frame-dropper support added to the rate control library.
* RTC Rate control improvements for low bitrate and for SVC.

- Compression Efficiency Improvements
* Improved accuracy of cost estimation for loop restoration and
global motion.
* Improved selection of loop restoration unit size - full search up
to (non-realtime) speed 2, retuned static selection at higher
* RTC Screen content mode: 3-5% bdrate gains across speeds 7 - 10.
* Good-quality mode: 0.2 - 0.5% bdrate gains across speeds 1 - 4.

- Perceptual Quality Improvements
* RTC Screen: Improved visual quality for scrolling.
* RTC: Improved color quality for both screen and video mode.

- Speedup and Memory Optimizations
* Good-quality, single-thread encoder speedups:
o 15% improvement for speed 5.
o 12% improvement for speed 6.
* Arm standard bitdepth VoD (--good):
o 8% speedup for speeds 0 and 1.
o 20% speedup for speed 2.
o 27% speedup for speed 3.
o 30% speedup for speed 4.
o 38% speedup for speeds 5 and 6.
* Arm high bitdepth VoD (--good):
o 206% speedup for speeds 0 and 1.
o 180% speedup for speed 2.
o 51% speedup for speeds 3 and 4.
o 68% speedup for speed 5.
o 72% speedup for speed 6.
* RTC Screen content: 2-6% speedup across speeds 7-10.
* RTC: 2-3% speedup for temporal layers.
* RTC: Speedups to reference scaling in nonrd pickmode.
* Good-quality mode: Simplified global motion estimation, saving
~1200 lines of code and 1KB of tables while improving quality.

- Bug Fixes
* Fixes to improve libaom stability in case of memory allocation
* Fixes to SIMD functions (x86 AVX2/SSE2 and ARM Neon).
* b/310457427, b/310766628: Bug fixes to only use rec_sse in CBR
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