libaom v3.14.0 release candidate 1

[Wan-Teh Chang]

Hi everyone,

libaom v3.14.0 release candidate 1 is available. The release tag is
v3.14.0-rc1. Your testing will be greatly appreciated.

This release is ABI compatible with the last release.

This release includes significant compression efficiency and
perceptual quality improvements for layered image encoding, in
addition to bug fixes.

The `build` directory in the source tree was removed and the original
build/cmake directory was moved up one level. If you use the CMake
toolchain files in the original build/cmake/toolchains directory,
they are now in the cmake/toolchains directory.

The unsupported aom_img_fmt_t enum constants AOM_IMG_FMT_AOMYV12 and
AOM_IMG_FMT_AOMI420 are deprecated and will be removed in a future
release. Do not use them.

The new codec controls AV1E_SET_EXTERNAL_RATE_CONTROL (including the
new aom_rc_funcs_t struct and the new "aom/aom_ext_ratectrl.h" and
"aom/aom_tpl.h" headers) and AV1E_GET_GOP_INFO (including the new
aom_gop_info_t struct) have the experimental API status and are NOT
part of the stable API. Applications that need the backward
compatibility of the stable API must not use
AV1E_SET_EXTERNAL_RATE_CONTROL and AV1E_GET_GOP_INFO.

- New Features
* Tuning modes AOM_TUNE_IQ and AOM_TUNE_SSIMULACRA2 now work with
inter-frame encoding modes (good-quality and realtime), enabling
efficient layered image encoding.
* Variance Boost (deltaq-mode 6) support has been extended to
include good-quality and realtime modes.
* New value 2 for use_fixed_qp_offsets: disallow the application of
per-frame QP offsets, enabling full control of each frame's QP, by
adjusting rc_cfg.cq_level between each encoded frame.
* Low-complexity mode support is extended to VOD encoding.
* New AOM_EFLAG_FREEZE_INTERNAL_STATE flag for aom_codec_encode() to
encode a frame without updating encoder state such as reference
buffers, CDF tables, and rate control state. Useful for
speculative encoding.
* New aom_matrix_coefficients_t enum constants:
- AOM_CICP_MC_IPT_C2 (15): IPT-C2
- AOM_CICP_MC_YCGCO_RE (16): YCgCo-Re
- AOM_CICP_MC_YCGCO_RO (17): YCgCo-Ro
* New aom_metadata_insert_flags_t enum constants for adding
layer-specific metadata OBUs:
- AOM_MIF_NON_KEY_FRAME_LAYER_SPECIFIC: Adds layer-specific
metadata if it's not a keyframe
- AOM_MIF_KEY_FRAME_LAYER_SPECIFIC: Adds layer-specific metadata
only if it's a keyframe
- AOM_MIF_ANY_FRAME_LAYER_SPECIFIC: Adds layer-specific metadata
to any type of frame
* Experimental: New codec control AV1E_SET_EXTERNAL_RATE_CONTROL to
enable an external rate control library. Not part of the stable
API.
* Experimental: New codec control AV1E_GET_GOP_INFO to get the GOP
structure from the encoder. Not part of the stable API.
* New codec control AOME_SET_VALIDATE_HBD_INPUT to validate high
bitdepth (HBD) input and ensure that every pixel is within the
valid range. The corresponding option for aom_codec_set_option()
is "validate-hbd-input".
* New codec control AOMD_SET_FRAME_SIZE_LIMIT to set the maximum
frame size for a decoder

- Compression Efficiency Improvements
* When encoding 2-layered images with AOM_TUNE_IQ vs. AOM_TUNE_SSIM:
- Good-quality mode: up to 15% gains at similar SSIMULACRA 2
scores.
- Realtime mode: up to 30% gains at similar SSIMULACRA 2 scores.
* Enable screen detection mode 2 (anti-aliased text and graphics
aware) in all-intra mode.
* Some minor quantization matrix formula and delta chroma q tweaks
for the AOM_TUNE_SSIMULACRA2 tuning mode, with up to 0.2%
SSIMULACRA 2 score efficiency gains.
* Re-tune and re-work encoder features, achieving coding gains at
each speed level and better coding efficiency vs complexity
tradeoff.
* RTC screen: improvements to quality and scroll detection for high
resolutions (>= 2K).

- Perceptual Quality Improvements
* AOM_TUNE_IQ improves the visual quality of layered image encoding
compared to AOM_TUNE_SSIM.
* Adaptive sharpness: tweak loop filter sharpness threshold to
improve visual quality at QPs 29 and 30.
* Improve encoder algorithms in loop restoration, CDEF, temporal
filter and rate control, delivering better visual quality.

- Speedups
* Make Adaptive CDEF more decoder friendly by limiting CDEF
application to only regions where high filter strengths are
needed.
* Encoder complexity is reduced significantly, especially at speed
1 to 3.
* Further AArch64 SIMD optimization of filtering algorithms,
particularly using Armv8.6 Neon I8MM.
* Additional tweaks to AArch64 Neon paths for quantization, SAD,
subpel variance and intra-predictors.

- Bug Fixes
* Commit 4cc0867f: fix multithreading crashes when loop restoration
filtering is used by the encoder.
* Commit 74aaa1ef: fix AOM_SCALING_MODE crashes when compound mask
prediction modes are used by the encoder.
* b:502030569: Avoid assertion failure in `read_uncompressed_header`
triggered by fuzzed input
* b:503197490: Fix an integer overflow in target bits calculation
* b:503691210: Avoid reference to uninitialized member variables for
multi workers.
* b:504317456: Handle buffer pointer in LAP mode to avoid overflow
* b:502133197: Avoid a bitread assertion failure in
get_av1config_from_obu()

Thanks,
Wan-Teh Chang