libaom-av1


libaom AV1 encoder wrapper.

Requires the presence of the libaom headers and library during configuration. You need to explicitly configure the build with --enable-libaom.

The wrapper supports the following standard libavcodec options:

'b'

Set bitrate target in bits/second. By default this will use variable-bitrate mode. If 'maxrate' and 'minrate' are also set to the same value then it will use constant-bitrate mode, otherwise if 'crf' is set as well then it will use constrained-quality mode.

'g keyint_min'

Set key frame placement. The GOP size sets the maximum distance between key frames; if zero the output stream will be intra-only. The minimum distance is ignored unless it is the same as the GOP size, in which case key frames will always appear at a fixed interval. Not set by default, so without this option the library has completely free choice about where to place key frames.

'qmin qmax'

Set minimum/maximum quantisation values. Valid range is from 0 to 63 (warning: this does not match the quantiser values actually used by AV1 - divide by four to map real quantiser values to this range). Defaults to min/max (no constraint).

'minrate maxrate bufsize rc_init_occupancy'

Set rate control buffering parameters. Not used if not set - defaults to unconstrained variable bitrate.

'threads'

Set the number of threads to use while encoding. This may require the 'tiles' or 'row-mt' options to also be set to actually use the specified number of threads fully. Defaults to the number of hardware threads supported by the host machine.

'profile'

Set the encoding profile. Defaults to using the profile which matches the bit depth and chroma subsampling of the input.

The wrapper also has some specific options:

'cpu-used'

Set the quality/encoding speed tradeoff. Valid range is from 0 to 8, higher numbers indicating greater speed and lower quality. The default value is 1, which will be slow and high quality.

'auto-alt-ref'

Enable use of alternate reference frames. Defaults to the internal default of the library.

'arnr-max-frames (frames)'

Set altref noise reduction max frame count. Default is -1.

'arnr-strength (strength)'

Set altref noise reduction filter strength. Range is -1 to 6. Default is -1.

'aq-mode (aq-mode)'

Set adaptive quantization mode. Possible values:

'none (0)'

Disabled.

'variance (1)'

Variance-based.

'complexity (2)'

Complexity-based.

'cyclic (3)'

Cyclic refresh.

'lag-in-frames'

Set the maximum number of frames which the encoder may keep in flight at any one time for lookahead purposes. Defaults to the internal default of the library.

'error-resilience'

Enable error resilience features:

'default'

Improve resilience against losses of whole frames.

Not enabled by default.

'crf'

Set the quality/size tradeoff for constant-quality (no bitrate target) and constrained-quality (with maximum bitrate target) modes. Valid range is 0 to 63, higher numbers indicating lower quality and smaller output size. Only used if set; by default only the bitrate target is used.

'static-thresh'

Set a change threshold on blocks below which they will be skipped by the encoder. Defined in arbitrary units as a nonnegative integer, defaulting to zero (no blocks are skipped).

'drop-threshold'

Set a threshold for dropping frames when close to rate control bounds. Defined as a percentage of the target buffer - when the rate control buffer falls below this percentage, frames will be dropped until it has refilled above the threshold. Defaults to zero (no frames are dropped).

'denoise-noise-level (level)'

Amount of noise to be removed for grain synthesis. Grain synthesis is disabled if this option is not set or set to 0.

'denoise-block-size (pixels)'

Block size used for denoising for grain synthesis. If not set, AV1 codec uses the default value of 32.

'undershoot-pct (pct)'

Set datarate undershoot (min) percentage of the target bitrate. Range is -1 to 100. Default is -1.

'overshoot-pct (pct)'

Set datarate overshoot (max) percentage of the target bitrate. Range is -1 to 1000. Default is -1.

'minsection-pct (pct)'

Minimum percentage variation of the GOP bitrate from the target bitrate. If minsection-pct is not set, the libaomenc wrapper computes it as follows: (minrate * 100 / bitrate). Range is -1 to 100. Default is -1 (unset).

'maxsection-pct (pct)'

Maximum percentage variation of the GOP bitrate from the target bitrate. If maxsection-pct is not set, the libaomenc wrapper computes it as follows: (maxrate * 100 / bitrate). Range is -1 to 5000. Default is -1 (unset).

'frame-parallel (boolean)'

Enable frame parallel decodability features. Default is true.

'tiles'

Set the number of tiles to encode the input video with, as columns x rows. Larger numbers allow greater parallelism in both encoding and decoding, but may decrease coding efficiency. Defaults to the minimum number of tiles required by the size of the input video (this is 1x1 (that is, a single tile) for sizes up to and including 4K).

'tile-columns tile-rows'

Set the number of tiles as log2 of the number of tile rows and columns. Provided for compatibility with libvpx/VP9.

'row-mt (Requires libaom >= 1.0.0-759-g90a15f4f2)'

Enable row based multi-threading. Disabled by default.

'enable-cdef (boolean)'

Enable Constrained Directional Enhancement Filter. The libaom-av1 encoder enables CDEF by default.

'enable-global-motion (boolean)'

Enable the use of global motion for block prediction. Default is true.

'enable-intrabc (boolean)'

Enable block copy mode for intra block prediction. This mode is useful for screen content. Default is true.