libaom v3.2.0 release candidate 1

[Wan-Teh Chang]

Hi everyone,

libaom v3.2.0 release candidate 1 is available. The release tag is
v3.2.0-rc1. Your testing will be greatly appreciated.

The code name of the libaom v3.2.0 release is Daring Do. The 'daringdo'
release branch is based at revision
e147ef20a27c7e2e1a37a97ad9093e84ae596aa8, which has been in use
internally at Google since Sep 21, 2021.

This release includes compression efficiency and perceptual quality
improvements, speedup and memory optimizations, as well as some new
features.

- New Features
* Introduced speeds 7, 8, and 9 for all-intra mode.
* Introduced speed 10 for real-time mode.
* Introduced an API that allows external partition decisions.

- Compression Efficiency Improvements
* Intra-mode search improvement.
* Improved real time (RT) mode BDrate savings by ~5% (RT speed 5)
and ~12% (RT speed 6). The improvement was measured on the video
conference set.

- Perceptual Quality Improvements
* Added a new mode --deltaq-mode=3 to improve perceptual quality
based on a differential contrast model for still images.
* Added a new mode –deltaq-mode=4 to improve perceptual quality
based on user rated cq_level data set for still images.

- Speedup and Memory Optimizations
* Further improved 2-pass good quality encoder speed:
o Speed 2 speedup: 18%
o Speed 3 speedup: 22%
o Speed 4 speedup: 37%
o Speed 5 speedup: 30%
o Speed 6 speedup: 20%
* Optimized the real time encoder (measured on the video conference
set):
o RT speed 5 speedup: 110%
o RT speed 6 speedup: 77%

Thanks,
Wan-Teh Chang