Release v3.1.0 Celestia

2021-05-03 v3.1.0
  This release adds an "all intra" mode to the encoder, which significantly
  speeds up the encoding of AVIF still images at speed 6.

  - Upgrading:
    All intra mode for encoding AVIF still images and AV1 all intra videos:
    AOM_USAGE_ALL_INTRA (2) can be passed as the 'usage' argument to
    aom_codec_enc_config_default().

    New encoder control IDs added:
      - AV1E_SET_ENABLE_DIAGONAL_INTRA: Enable diagonal (D45 to D203) intra
        prediction modes (0: false, 1: true (default)). Also available as
        "enable-diagonal-intra" for the aom_codec_set_option() function.

    New aom_tune_metric enum value: AOM_TUNE_BUTTERAUGLI. The new aomenc option
    --tune=butteraugli was added to optimize the encoder’s perceptual quality by
    optimizing the Butteraugli metric. Install libjxl (JPEG XL) and then pass
    -DCONFIG_TUNE_BUTTERAUGLI=1 to the cmake command to enable it.

    Addition of support for libvmaf 2.x.

  - Enhancements:
    Heap memory consumption for encoding AVIF still images is significantly
    reduced.

  - Bug fixes:
    Issue 2601: third_party/libaom fails licensecheck

    Issue 2950: Conditional expression for rc->this_key_frame_forced is always
    true in find_next_key_frame()

    Issue 2988: "make install" installs the aom.h header twice

    Issue 2992: Incorrectly printing the temporal_id twice in dump_obu tool

    Issue 2998:

    Issue 2999:

    Issue 3000: