libaom v3.11.0 release candidate 1

[Jerome Jiang]

Hi everyone,

libaom v3.11.0 release candidate 1 is available. The release tag is
v3.11.0-rc1. Your testing will be greatly appreciated.

This release includes an experimental encoder initialization flag, perceptual
quality improvements, binary size reduction under certain configurations and
many bug fixes. This release changes the default encoder configuration for the
AOM_USAGE_REALTIME mode. This release is ABI compatible with the last release.

  - New Features
    * An experimental flag AOM_CODEC_USE_PRESET is added to allow users to use
      default settings from the library without specifying all the codec
      controls. This must be used together with the AOM_CODEC_USE_EXPERIMENTAL
      flag, and your application must be recompiled and relinked when libaom is
      upgraded to a future release.

  - Perceptual Quality Improvements
    * Visual quality improvements for RTC screen content
      * Higher quality on scene or slide changes
      * Faster quality ramp-up for static content after scene change
      * Quality improvements for screen content with active maps

  - Speedup
    * Added and improved Neon SIMD paths for dynamic frame scaling with ~1.5%
      overall encoding speedup.

  - Other Improvements
    * Binary size reduction: 10% compared with last release, with
      CONFIG_REALTIME_ONLY enabled, CONFIG_AV1_DECODER and
      CONFIG_AV1_HIGHBITDEPTH disabled.
    * Update default_extra_cfg for CONFIG_REALTIME_ONLY to provide proper RTC
      defaults settings
    * Change the default valuess of the following encoder config options in the
      AOM_USAGE_REALTIME mode:
      *  rc_overshoot_pct and rc_undershoot_pct are changed from 25 to 50
      *  rc_buf_sz is changed from 6000 to 1000
      *  rc_buf_initial_sz is changed from 4000 to 600
      *  rc_buf_optimal_sz is changed from 5000 to 600

  - Bug Fixes
    * aomedia:363016123: rtc: Fix setting of intra-only frame for
      set_ref_frame_config and add checks
    * aomedia:42302583: rtc: Fix for artifacts for screen with active_maps
    * b:365088425: rtc: Allow for lower-QP on scene/slide changes
    * b:367285382: Fix to encoder quality max-out too early for screen
    * b:362936830: rtc: Allow QP to decrease more aggressively for static
      content
    * b:361617762: Clamp the calculation of sb64_target_rate to INT_MAX
    * chromium:362123224: rtc-svc: Reset ref_map_idx for references not used
    * chromium:367892770: Fix to possible integer overflow in reset_rc
    * webrtc:369633254: rtc-svc: Fix to reset ref_idx for svc
    * Fix exit condition in rate correction update

Thanks.