libaom v3.4.0 release candidate 1

[Wan-Teh Chang]

Hi everyone,

libaom v3.4.0 release candidate 1 is available. The release tag is
v3.4.0-rc1. Your testing will be greatly appreciated.

The code name of the libaom v3.4.0 release is Fluttershy. The
'fluttershy' release branch is based at revision
32d6783c4c9f6e78f43bd4ceffaa0eb2143aed57, which has been in use
internally at Google since May 21, 2022.

This release includes compression efficiency and perceptual quality
improvements, speedup and memory optimizations, and some new features.
There are no ABI or API breaking changes in this release.

- New Features
* New --dist-metric flag with "qm-psnr" value to use quantization
matrices in the distortion computation for RD search.
* New command line option "--auto-intra-tools-off=1" to make
all-intra encoding faster for high bit rate under
"--deltaq-mode=3" mode.
* New rate control library aom_av1_rc for real-time hardware
encoders. Supports CBR for both one spatial layer and SVC.
* New image format AOM_IMG_FMT_NV12 can be used as input to the
encoder. The presence of AOM_IMG_FMT_NV12 can be detected at
compile time by checking if the macro AOM_HAVE_IMG_FMT_NV12 is
defined.

- Compression Efficiency Improvements
* Correctly calculate SSE for high bitdepth in skip mode, 0.2% to
0.6% coding gain.
* RTC at speed 9/10: BD-rate gain of ~4/5% and speedup of ~10/5%
* RTC screen content coding: many improvements for real-time screen
at speed 10 (quality, speedup, and rate control), up to high
resolutions (1080p).
* RTC-SVC: fixes to make intra-only frames work for spatial layers.
* RTC-SVC: quality improvements for temporal layers.
* AV1 RT: A new passive rate control strategy for screen content, an
average of 7.5% coding gain, with some clips of 20+%. The feature
is turned off by default due to higher bit rate variation.

- Perceptual Quality Improvements
* RTC: Visual quality improvements for high speeds (9/10)

- Speedup and Memory Optimizations
* Ongoing improvements to intra-frame encoding performance on Arm
* Faster encoding speed for "--deltaq-mode=3" mode.

- Bug Fixes
* b/204460717: README.md: replace master with main
* b/210677928: libaom disable_order is surprising for
max_reference_frames=3
* b/222461449: -DCONFIG_TUNE_BUTTERAUGLI=1 broken
* b/227207606: write_greyscale writes incorrect chroma in highbd
mode
* b/229955363: Integer-overflow in linsolve_wiener
* https://crbug.com/aomedia/2032
* https://crbug.com/aomedia/2397
* https://crbug.com/aomedia/2563
* https://crbug.com/aomedia/2815
* https://crbug.com/aomedia/3009
* https://crbug.com/aomedia/3018
* https://crbug.com/aomedia/3045
* https://crbug.com/aomedia/3101
* https://crbug.com/aomedia/3130
* https://crbug.com/aomedia/3173
* https://crbug.com/aomedia/3184
* https://crbug.com/aomedia/3187
* https://crbug.com/aomedia/3190
* https://crbug.com/aomedia/3195
* https://crbug.com/aomedia/3197
* https://crbug.com/aomedia/3201
* https://crbug.com/aomedia/3202
* https://crbug.com/aomedia/3204
* https://crbug.com/aomedia/3205
* https://crbug.com/aomedia/3207
* https://crbug.com/aomedia/3208
* https://crbug.com/aomedia/3209
* https://crbug.com/aomedia/3213
* https://crbug.com/aomedia/3214
* https://crbug.com/aomedia/3219
* https://crbug.com/aomedia/3222
* https://crbug.com/aomedia/3223
* https://crbug.com/aomedia/3225
* https://crbug.com/aomedia/3226
* https://crbug.com/aomedia/3228
* https://crbug.com/aomedia/3232
* https://crbug.com/aomedia/3236
* https://crbug.com/aomedia/3237
* https://crbug.com/aomedia/3238
* https://crbug.com/aomedia/3240
* https://crbug.com/aomedia/3243
* https://crbug.com/aomedia/3244
* https://crbug.com/aomedia/3246
* https://crbug.com/aomedia/3248
* https://crbug.com/aomedia/3250
* https://crbug.com/aomedia/3251
* https://crbug.com/aomedia/3252
* https://crbug.com/aomedia/3255
* https://crbug.com/aomedia/3257
* https://crbug.com/aomedia/3259
* https://crbug.com/aomedia/3260
* https://crbug.com/aomedia/3267
* https://crbug.com/aomedia/3268
* https://crbug.com/aomedia/3269
* https://crbug.com/aomedia/3276
* https://crbug.com/aomedia/3278
* https://crbug.com/chromium/1290068
* https://crbug.com/chromium/1303237
* https://crbug.com/chromium/1304990
* https://crbug.com/chromium/1321141
* https://crbug.com/chromium/1321388
* https://crbug.com/oss-fuzz/44846
* https://crbug.com/oss-fuzz/44856
* https://crbug.com/oss-fuzz/44862
* https://crbug.com/oss-fuzz/44904
* https://crbug.com/oss-fuzz/45056

Thanks,
Wan-Teh Chang