aom-psy101

damian101/aom-psy101

Latest release

2023-12-03Dec 2, 2023

Last commit

Jun 2, 2026

License

BSD-2-Clause

Stars

7

aom-psy101 is a fork of libaom/aomenc maintained by Damian Höster (damian101) at gitlab.com/damian101/aom-psy101. It combines selected patches from aom-av1-psy and aom-av1-lavish with its own changes, and it keeps tracking current libaom.

Status: the default psy101 branch last merged upstream libaom on 2 June 2026, and the binary reports 3.14.1-174-g74890d72b. The fork’s own changes were last updated on 21 February 2025. The project has no release builds and no usage documentation beyond --help.

This page covers only what the fork changes. For rate control, presets, Av1an usage, grain synthesis and the other mainline options, see aomenc.

Building

git clone https://gitlab.com/damian101/aom-psy101.git
cmake -S aom-psy101 -B psy101_build -DCMAKE_BUILD_TYPE=Release -DENABLE_TESTS=0 -DENABLE_DOCS=0
cmake --build psy101_build -j"$(nproc)"

psy101_build/aomenc --help should list AOMedia Project AV1 Encoder Psy101. Av1an runs whichever aomenc comes first in PATH, so put the fork’s binary there or in a directory you prepend. FFmpeg’s libaom-av1 uses the fork only if FFmpeg is built against the fork’s libaom.

Encoding

The fork’s defaults are already perceptually oriented, so a plain constant-quality command is a good start:

aomenc --end-usage=q --cq-level=24 --bit-depth=10 -o output.webm input.y4m

Add --tune-content=psy101 to use the fork’s preset (described below). Everything else works as in mainline: piping, two-pass behaviour and Av1an usage are described on the aomenc page.

Defaults that differ from mainline

Option	psy101	Mainline 3.15.1
--cpu-used	4 (good-quality range 0–9)	0 (0–6)
--tune	ssim	psnr
--enable-qm, --qm-min	1, 0 (4 in all-intra)	0, 5
--kf-min-dist	12	0
--enable-chroma-deltaq	1	0
--quant-b-adapt	1	0
--enable-cdef	0 (off)	1
--arnr-strength, --arnr-maxframes	2 (range 0–4), 15	5 (0–6), 7
--lag-in-frames maximum	128	48
--denoise-block-size	16	32
Automatic tiling	--auto-tiling=3	--auto-tiles=0

CDEF, AV1’s deringing filter, is off by default. If ringing or mosquito noise shows up around edges at lower bitrates, turn it back on with --enable-cdef=1, or use --enable-cdef=3 for CDEF that adapts to the frame qindex.

Fork-specific options

Option	Default	What it does
--tune-content=psy101	—	Applies the fork’s preset. It disables loop restoration and 64-point transforms, forces 64×64 superblocks and caps the GF pyramid height at 4. It uses perceptual delta-q (--deltaq-mode=2) in two-pass encodes and Variance Boost (--deltaq-mode=6) in all-intra mode, whatever --deltaq-mode says.
--tune-content=psy	—	Perceptual adjustments to intra-mode, partition and RD decisions without the psy101 tool restrictions. It was retuned for low-bitrate encoding in January 2025.
--tune=image_perceptual_quality	—	An SSIM-style tune that scales rate–distortion decisions with libaom’s user-rating variance model, adjusted by cq-level. Mainline’s iq and ssimulacra2 tunes are also available.
--luma-bias	0	0–15. Lowers the RD multiplier in dark blocks so they get more bits, which counters crushed or blocky shadows. It is ignored for PQ (smpte2084) and log transfer characteristics.
--auto-tiling	3	0–7. Sets the minimum tile size: higher values pick more, smaller tiles for better encoder and decoder threading, so the default already tiles larger frames. Values above 5 also force 64×64 superblocks. Explicit --tile-columns and --tile-rows take precedence. With Av1an, set --auto-tiling=0 to avoid tiles.
--fast-decode	0	0–3. Trades efficiency for easier decoding. Level 1 and above cap the GF pyramid height, 2 and above also disable loop restoration, and 3 also enables frame-parallel decoding mode.
--ssim-rd-mult	100	Scales the SSIM-based RD multiplier used by --tune=ssim, iq, ssimulacra2 and image_perceptual_quality.
--ssim-vmaf-rd, --vmaf-rd-resize	0, 1	Mix SSIM RD into VMAF RD (percent) and set the VMAF RD downscale. They need a build with -DCONFIG_TUNE_VMAF=1.

Complete native parameter reference

Every option aomenc accepts at psy101 commit 74890d72 (libaom 3.14.1 plus later upstream commits), including those that need optional build features. Defaults are for good-quality mode; rows note where the fork changes a default or behaviour, or where its --help text is wrong.

Application and output (19 options)

Option	Default	Description
--help	—	Print the full option list and exit.
--cfg, -c	unset	Read low-level tool settings from a key–value file in the format of libaom’s Sample.cfg. Only the first --cfg is used.
--debug, -D	off	Leave the application version out of the WebM tags so that repeated encodes are byte-identical.
--output, -o	required	Output file. A .ivf or .obu extension selects that format unless --webm is given; any other name gets WebM.
--codec	av1	Encoder to use. libaom builds contain only av1.
--limit	0 (all frames)	Stop after this many input frames.
--skip	0	Skip this many input frames before encoding.
--quiet, -q	off	Do not print progress.
--verbose, -v	off	Print the encoder configuration before encoding.
--psnr	0 (off)	Report PSNR: 1 at the input bit depth, 2 at the stream bit depth. --psnr without a value means 1.
--test-decode	off	Decode every frame while encoding and compare it with the encoder’s reconstruction: warn reports a mismatch, fatal stops the encode.
--webm	on	WebM output. Requires a build with WebM I/O (CONFIG_WEBM_IO, on by default); without it the default output is raw OBU.
--ivf	off	IVF output, the minimal frame container used by libaom’s own tools and test vectors.
--obu	off	Raw low-overhead OBU stream (AV1 Section 5) with no container.
--annexb	0 (off)	Write the length-delimited Annex B bitstream format instead of Section 5 OBUs. Range 0–1.
--q-hist	0 (off)	After encoding, print a histogram of frame quantisers with this many buckets.
--rate-hist	0 (off)	After encoding, print a histogram of frame bitrates with this many buckets.
--disable-warnings	off	Suppress the warnings about questionable settings.
--disable-warning-prompt, -y	off	Print those warnings but do not stop to ask whether to continue.

Usage modes and passes (12 options)

Option	Default	Description
--good	selected	Good-quality mode (--usage=0), the normal mode for offline video.
--rt	off	Realtime mode (--usage=1): one pass, no lookahead, speeds 5–12, for low-latency streaming and conferencing.
--allintra	off	All-intra mode (--usage=2): every frame is a keyframe, no lookahead, speeds 0–9. Meant for still images and image sequences; it also turns CDEF off and changes the QM range and screen-content detection defaults.
--usage, -u	0 (good)	Usage mode by number: 0 good quality, 1 realtime, 2 all-intra. Same as --good, --rt and --allintra.
--passes, -p	2 (1 in realtime and all-intra)	Number of passes, 1–3. Two-pass good-quality encodes use the first-pass statistics even in q mode; realtime and all-intra always run one pass. Three passes add a half-resolution second pass whose decisions guide the final pass.
--pass	all passes	Run only pass 1, 2 or 3 of a multi-pass encode, so that the passes can run as separate processes (each needs the same --fpf).
--fpf	in memory	First-pass statistics file. Needed when passes run as separate processes; otherwise the statistics stay in memory.
--two-pass-output	<output>_pass2_<n>.ivf	Three-pass encoding: IVF file that receives the second (downscaled) pass.
--second-pass-log, -spf	unset	Three-pass encoding: file in which the second pass stores its GOP and TPL decisions for the third pass.
--two-pass-input	unset	Three-pass encoding: an already-downscaled source to read in the second pass instead of scaling the input to half size.
--two-pass-width	0 (half the input)	Three-pass encoding: frame width of the second pass (and of raw --two-pass-input).
--two-pass-height	0 (half the input)	Three-pass encoding: frame height of the second pass (and of raw --two-pass-input).

Input format (20 options)

Option	Default	Description
--i420	on for raw input	Raw input is 4:2:0 planar (I420). Y4M input takes its format from the header.
--yv12	off	Raw input is YV12 (4:2:0 planar with V before U).
--nv12	off	Raw input is NV12 (4:2:0 with interleaved U and V).
--i422	off	Raw input is 4:2:2 planar.
--i444	off	Raw input is 4:4:4 planar.
--width, -w	from Y4M	Frame width in pixels. Required for raw input.
--height, -h	from Y4M	Frame height in pixels. Required for raw input.
--fps	from Y4M (raw: 30/1)	Frame rate as a fraction, e.g. 24000/1001.
--timebase	1/fps	Timestamp precision in fractional seconds. aomenc overwrites it with the inverse frame rate before encoding, so setting it has no effect.
--bit-depth, -b	8 (or the input’s, if higher)	Bit depth of the encoded stream: 8, 10 or 12. Encoding 8-bit sources at 10 bits reduces banding and usually improves efficiency.
--input-bit-depth	from Y4M (raw: --bit-depth)	Bit depth of raw input when it differs from the stream bit depth.
--input-chroma-subsampling-x	0	Horizontal chroma subsampling (0 or 1) of 12-bit raw input in profile 2. Y4M input supplies it from the header.
--input-chroma-subsampling-y	0	Vertical chroma subsampling (0 or 1) of 12-bit raw input in profile 2.
--profile	0 (Main)	AV1 profile: 0 Main (4:2:0 and monochrome, 8–10 bit), 1 High (adds 4:4:4), 2 Professional (adds 4:2:2 and 12 bit). aomenc raises it when the input needs a higher profile.
--monochrome	off	Encode luma only, with no chroma planes.
--use-16bit-internal	off (on above 8 bit)	Use the high-bit-depth (16-bit) pipeline for an 8-bit encode.
--validate-hbd-input	1 (on)	Check that every high-bit-depth input sample lies within the range of the bit depth. Range 0–1.
--stereo-mode	mono	Stereo 3D layout written to the WebM header: mono, left-right, bottom-top, top-bottom or right-left. Requires a build with WebM I/O.
--forced_max_frame_width	0 (first frame)	Maximum frame width written to the sequence header, so that later frames (for example after a resize) may be wider than the first.
--forced_max_frame_height	0 (first frame)	Maximum frame height written to the sequence header.

Rate control (24 options)

Option	Default	Description
--end-usage	vbr (q in all-intra, cbr in realtime)	Rate-control mode: vbr, cbr, cq (constrained quality: --cq-level capped by --target-bitrate) or q (constant quality at --cq-level). Quality-targeted encodes use q.
--target-bitrate	256	Target bitrate in kbit/s for vbr and cbr, and the bitrate cap in cq mode.
--cq-level	10	Quality level for q and cq modes, 0–63; lower is better. It maps to qindex 4×N (255 at 63). The scale does not match x264, x265 or SVT-AV1 CRF values.
--min-q	0	Best (lowest) quantiser rate control may use, 0–63. In q mode --cq-level must not be below it.
--max-q	63	Worst (highest) quantiser rate control may use, 0–63.
--lossless	0 (off)	Mathematically lossless coding (qindex 0 with the lossless transform). Range 0–1.
--undershoot-pct	25 (50 in realtime)	How far below the target bitrate a GOP may fall, in percent (0–100), before rate control compensates.
--overshoot-pct	25 (50 in realtime)	How far above the target bitrate a GOP may go, in percent (0–100), before rate control compensates.
--buf-sz	6000 (1000 in realtime)	Decoder buffer size in milliseconds at the target bitrate, for the rate-control buffer model.
--buf-initial-sz	4000 (600 in realtime)	Initial decoder buffer fill in milliseconds.
--buf-optimal-sz	5000 (600 in realtime)	Target decoder buffer fill in milliseconds.
--bias-pct	50	Two-pass VBR bit distribution, 0–100: 0 spreads bits evenly like CBR, 100 follows frame complexity fully. Ignored in one pass.
--minsection-pct	0	Lowest bitrate a GOP may get in two-pass VBR, as a percentage of the target. Ignored in one pass.
--maxsection-pct	2000	Highest bitrate a GOP may get in two-pass VBR, as a percentage of the target. Ignored in one pass.
--drop-frame	0 (off)	Drop frames when the rate buffer falls below this fill level (percent, 0–100). Used with CBR.
--max-intra-rate	0 (unlimited)	Cap on keyframe size as a percentage of the average frame size (450 allows 4.5 frames’ worth).
--max-inter-rate	0 (unlimited)	Cap on inter-frame size as a percentage of the average frame size.
--gf-cbr-boost	0 (off)	Extra bits for golden frames in CBR mode, as a percentage of the average frame bitrate.
--frame-boost	0 (off)	Periodic quantiser boost (0–1). The setting is accepted but the AV1 encoder does not use it.
--vbr-corpus-complexity-lap	0 (off)	One-pass VBR with lookahead only: average complexity per macroblock of the content corpus (0–10000), used to distribute bits.
--min-cr	0 (off)	Minimum compression ratio per frame ×100 (850 means 8.5:1), used to stay within level limits.
--use-fixed-qp-offsets	0 (adaptive)	q mode only: 0 derives per-layer quantiser offsets from --cq-level adaptively, 1 uses fixed offsets, 2 codes every frame at --cq-level with no offsets.
--fixed-qp-offsets	unset	Meant to give five offsets (keyframe, ALTREF and three internal alt-ref levels). aomenc only uses it to switch on --use-fixed-qp-offsets=1 and ignores the values.
--sb-qp-sweep	0 (off)	Try several quantisers per superblock and keep the one with the lowest RD cost. Intended for libaom’s unit tests; very slow.

Keyframes and GOP structure (12 options)

Option	Default	Description
--kf-min-dist	12	Minimum keyframe interval in frames. Set it equal to --kf-max-dist for a fixed interval. Mainline defaults to 0.
--kf-max-dist	9999 (0 in all-intra)	Maximum keyframe interval in frames; scene-cut keyframes can come sooner. For standalone encodes set it to the seek granularity you want, e.g. ten seconds of frames.
--disable-kf	off	Place no keyframes after the first frame. Av1an sets this for each chunk.
--enable-fwd-kf	0 (off)	Forward keyframes (open GOP): the keyframe is coded early as an alt-ref, so frames shown before it can reference it. Range 0–1.
--fwd-kf-dist	-1 (off)	Distance in frames between repeated forward keyframes.
--sframe-dist	0 (off)	Insert a switch frame (S-frame, a point where a player can switch between streams) every N frames.
--sframe-mode	1	S-frame placement, 1–2: 1 turns the frame into an S-frame only if it is an alt-ref, 2 uses the next alt-ref.
--min-gf-interval	0 (auto)	Shortest golden-frame group (distance between alt-refs) in frames, up to 127.
--max-gf-interval	0 (auto)	Longest golden-frame group in frames, 2–127.
--gf-min-pyr-height	0	Minimum depth of the hierarchical reference pyramid in a GF group, 0–5.
--gf-max-pyr-height	5	Maximum depth of the hierarchical reference pyramid in a GF group, 0–5. Lower values mean fewer reference layers and less temporal quality variation. --tune-content=psy101 and --fast-decode lower the default 5 to 4.
--kf-max-pyr-height	-1 (off)	Maximum pyramid depth for the GF group that starts at a keyframe, −1–5; the smaller of this and --gf-max-pyr-height applies.

Lookahead, alt-refs and temporal filtering (7 options)

Option	Default	Description
--lag-in-frames	35 (0 in realtime and all-intra)	Lookahead in frames for frame-type, alt-ref and rate-control decisions, 0–128 (mainline allows 48). Larger values use more memory.
--auto-alt-ref	1 (on)	Use alternate reference frames: hidden, temporally filtered frames that the frames around them predict from. Values above 1 are treated as 1.
--enable-overlay	1 (on)	Code an overlay frame where a filtered alt-ref is displayed. With 0 the filtered alt-ref is shown as it is.
--enable-tpl-model	1 (on)	Temporal dependency model (TPL): estimates how much later frames reference each block and spends bits accordingly. Required by --deltaq-mode=1.
--enable-keyframe-filtering	1	Temporal filtering of keyframes: 0 off, 1 on, 2 on with an overlay frame (experimental; can break seeking in players).
--arnr-maxframes	15	Number of frames, 0–15, that the alt-ref temporal filter averages; 0 or 1 disables filtering. Mainline defaults to 7.
--arnr-strength	2	Alt-ref temporal filter strength, 0–4 (mainline allows 0–6 and defaults to 5). Lower values keep more fine detail.

Speed and tuning (11 options)

Option	Default	Description
--cpu-used	4	Speed preset; lower is slower and more efficient. Good-quality mode accepts 0–9, but as in mainline its speed features stop at 6; realtime uses 5–12 and all-intra 0–9. Mainline defaults to 0.
--tune	ssim	Metric that RD decisions optimise: ssim, psnr, image_perceptual_quality (the fork’s SSIM-based tune, scaled by libaom’s user-rating variance model and adjusted by --cq-level), mainline’s iq and ssimulacra2, butteraugli (requires -DCONFIG_TUNE_BUTTERAUGLI=1), the vmaf* tunes (require -DCONFIG_TUNE_VMAF=1 and --vmaf-model-path) and vmaf_saliency_map (requires -DCONFIG_SALIENCY_MAP=1). Mainline defaults to psnr.
--tune-content	default	Content type: screen, film (synthesised grain with a fixed pattern), psy (perceptual intra-mode, partition and RD adjustments) and psy101, the fork’s preset: it also disables loop restoration and 64-point transforms, forces 64×64 superblocks, caps the GF pyramid at 4 and uses --deltaq-mode=2 in two-pass encodes and 6 in all-intra, whatever --deltaq-mode says.
--dist-metric	psnr	Distortion measure inside block decisions: psnr, or qm-psnr, which weights errors by the quantisation matrices (set by --tune=iq and ssimulacra2).
--sharpness	0	Bias, 0–7, of coefficient RD decisions towards keeping block detail. In all-intra mode it also sets the bitstream’s loop-filter sharpness, which weakens deblocking on block edges.
--enable-adaptive-sharpness	0 (off)	Vary the effective sharpness with the frame quantiser, using --sharpness as the maximum; reduces blocking at low and medium quality. No effect while --sharpness is 0. --tune=iq turns it on.
--screen-detection-mode	1 (2 in all-intra)	Screen-content detection: 1 standard, 2 also recognises anti-aliased text and graphics.
--enable-low-complexity-decode	0 (off)	Restrict tools so the stream is cheaper to decode. It only applies to good-quality speeds 1–3 when the shorter frame side is 608–1080 pixels.
--static-thresh	0	Motion threshold inherited from VP8/VP9. The setting is accepted but the AV1 encoder does not use it.
--noise-sensitivity	0 (off)	Temporal denoiser strength, 0–6, for realtime encodes. Requires a build with -DCONFIG_AV1_TEMPORAL_DENOISING=1 and only acts on 8-bit encodes at speed 8 and above.
--vmaf-model-path	/usr/local/share/model/vmaf_v0.6.1.json	VMAF model file used by the vmaf* tunes. Requires a build with -DCONFIG_TUNE_VMAF=1.

Adaptive quantisation and delta-q (8 options)

Option	Default	Description
--deltaq-mode	1 (objective)	Per-superblock quantiser modulation: 0 off; 1 objective, from the TPL model; 2 perceptual (wavelet energy); 3 perceptual for all-intra; 4 user-rating-based (all-intra); 5 HDR (BT.2020 input); 6 Variance Boost, which gives flat, low-variance areas more bits. Modes 1 and 2 need --enable-tpl-model=1. --tune-content=psy101 overrides it.
--deltaq-strength	100	Strength of --deltaq-mode=4 and 6, in percent (0–1000).
--delta-lf-mode	0 (off)	Also vary the loop-filter level per superblock. Only works with a non-zero --deltaq-mode. Range 0–1.
--aq-mode	0 (off)	Segment-based adaptive quantisation, separate from delta-q: 0 off, 1 variance, 2 complexity, 3 cyclic refresh (realtime).
--enable-chroma-deltaq	1 (on)	Chroma quantiser offsets. In all-intra mode with --tune=iq or ssimulacra2 they follow mainline’s subsampling-dependent values; otherwise 4:2:0 gets no offset and 4:2:2 and 4:4:4 get +3 and +6 qindex (coarser chroma). Mainline defaults to 0.
--enable-rate-guide-deltaq	0 (off)	All-intra only: rate-guided delta-q from a per-16×16-block rate file given with --rate-distribution-info. Needs --deltaq-mode=3.
--rate-distribution-info	./rate_map.txt	Rate-distribution file for --enable-rate-guide-deltaq.
--auto-intra-tools-off	0 (off)	All-intra with --deltaq-mode=3: let the encoder switch off intra tools that rarely pay off.

Quantisation (5 options)

Option	Default	Description
--enable-qm	1 (on)	Quantisation matrices: quantise high frequencies more coarsely than low ones. Commonly enabled for perceptual encodes. Mainline defaults to 0.
--qm-min	0 (4 in all-intra)	Lowest QM level, 0–15 (15 is flat, lower levels weight frequencies more strongly). The level used rises with the quantiser from --qm-min to --qm-max. Mainline defaults to 5.
--qm-max	9 (10 in all-intra)	Highest QM level, 0–15.
--quant-b-adapt	1 (on)	Adaptive quantiser: a wider dead zone for the trailing (highest-frequency) coefficients of each block, and a lone ±1 coefficient is dropped. Saves bits on fine noise. Mainline defaults to 0.
--disable-trellis-quant	3	Trellis (RD-optimised) coefficient quantisation: 0 always, 1 never, 2 not during the RD search, 3 not in the fast luma RD estimate.

Threads and tiles (10 options)

Option	Default	Description
--threads, -t	0 (one thread)	Maximum number of worker threads. aomenc stays single-threaded unless this is set.
--row-mt	1 (on)	Row-based multithreading inside tiles; needs --threads above 1. Range 0–1.
--fp-mt	0 (off)	Frame-parallel multithreading: encode several frames at once for more speed with many threads, at a small efficiency cost. Range 0–1.
--tile-columns	0	Number of tile columns as log2, 0–6 (2 means four columns). Tiles let encoder and decoder work in parallel but cost some efficiency; the frame width limits how many are possible. A non-zero value takes precedence over --auto-tiling.
--tile-rows	0	Number of tile rows as log2, 0–6. A non-zero value takes precedence over --auto-tiling.
--tile-width	unset (uniform)	Non-uniform tile widths in superblocks, comma-separated; the list repeats across the frame. Needs --tile-height as well.
--tile-height	unset (uniform)	Non-uniform tile heights in superblocks, comma-separated; the list repeats down the frame.
--large-scale-tile	0 (off)	Large-scale tile coding for random access to individual tiles (light-field and VR use). IVF output only. Range 0–1.
--num-tile-groups	1	Maximum number of tile groups (OBUs) per frame. --mtu-size overrides it.
--mtu-size	0 (off)	Maximum bytes per tile group, for packetised transport. A single tile larger than this still goes in one group.

Partitioning and superblocks (7 options)

Option	Default	Description
--sb-size	dynamic	Superblock size: dynamic (the encoder picks 64×64 or 128×128 from resolution and speed), 64 or 128. --tune-content=psy101 and --auto-tiling above 5 force 64.
--enable-rect-partitions	1 (on)	Rectangular partitions (horizontal and vertical halves).
--enable-ab-partitions	1 (on)	AB partitions: a split into one half and two quarters.
--enable-1to4-partitions	1 (on)	1:4 and 4:1 partitions (four horizontal or vertical strips).
--min-partition-size	4	Smallest block size searched: 4, 8, 16, 32, 64 or 128. At 4K and above, or at faster speeds, it is at least 8.
--max-partition-size	128	Largest block size searched: 4, 8, 16, 32, 64 or 128.
--partition-info-path	.	Directory for partition statistics read and written by libaom’s partition experiments.

Intra prediction (11 options)

Option	Default	Description
--enable-directional-intra	1 (on)	Directional (angular) intra modes.
--enable-diagonal-intra	1 (on)	The diagonal subset of directional modes (D45 to D203). No effect when directional modes are off.
--enable-angle-delta	1 (on)	Fine angle offsets (up to ±3 steps of 3°) on directional modes.
--enable-intra-edge-filter	1 (on)	Smoothing and upsampling of the reference edge used for directional prediction.
--enable-smooth-intra	1 (on)	Smooth, smooth-horizontal and smooth-vertical intra modes, which interpolate between edges.
--enable-paeth-intra	1 (on)	Paeth intra predictor, which picks the left, top or top-left neighbour per pixel.
--enable-filter-intra	1 (on)	Filter-intra modes: recursive filtered prediction in 4×2 cells, for smooth texture.
--enable-cfl-intra	1 (on)	Chroma from luma: chroma predicted from the reconstructed luma.
--enable-palette	1 (on)	Palette mode, which codes a block as up to eight colours. Used only when screen-content tools are active.
--enable-intrabc	1 (on)	Intra block copy from an already coded area of the same frame. Used only in intra frames with screen-content tools.
--force-video-mode	0 (off)	Use video coding settings even when only one frame is encoded, instead of still-picture settings.

Inter prediction (16 options)

Option	Default	Description
--max-reference-frames	7	Maximum number of reference frames searched per frame, 3–7.
--reduced-reference-set	0 (off)	Search a reduced set of single and compound references, which is faster.
--enable-order-hint	1 (on)	Frame order hints. Distance-weighted compound, temporal motion-vector projection and reference sign bias depend on them.
--enable-ref-frame-mvs	1 (on)	Temporal motion-vector prediction from the motion fields of reference frames.
--enable-dual-filter	1 (on)	Separate interpolation filters for horizontal and vertical sub-pixel motion.
--enable-global-motion	1 (on)	Frame-level global motion models for camera pans, zooms and rotation.
--enable-warped-motion	1 (on)	Local warped motion: a per-block affine model derived from neighbouring motion vectors.
--enable-obmc	1 (on)	Overlapped block motion compensation: blends in predictions made with neighbouring blocks’ motion to soften block edges.
--enable-dist-wtd-comp	1 (on)	Distance-weighted compound prediction, weighting two references by their temporal distance. Off when order hints are off.
--enable-onesided-comp	1 (on)	Compound prediction from two references on the same side (both past or both future).
--enable-masked-comp	1 (on)	Masked compound prediction (wedge and difference-weighted); 0 turns both off.
--enable-diff-wtd-comp	1 (on)	Difference-weighted compound, with a mask derived from the difference between the two predictions.
--enable-interinter-wedge	1 (on)	Wedge-shaped masks for compound prediction from two references.
--enable-interintra-comp	1 (on)	Inter-intra prediction: an inter prediction blended with an intra prediction.
--enable-smooth-interintra	1 (on)	Smooth (gradual) blending for inter-intra prediction.
--enable-interintra-wedge	1 (on)	Wedge-shaped masks for inter-intra prediction.

Transforms (8 options)

Option	Default	Description
--enable-tx64	1 (on)	64-point transforms for blocks of 64 pixels and larger. --tune-content=psy101 turns it off.
--enable-flip-idtx	1 (on)	Extended transform types: flipped ADST, identity and one-dimensional (horizontal or vertical) transforms.
--enable-rect-tx	1 (on)	Rectangular transforms. They need rectangular partitions.
--enable-tx-size-search	1 (on)	Search the transform size per block. With 0 each block uses its largest possible transform.
--reduced-tx-type-set	0 (off)	Search a reduced set of transform types, which is faster.
--use-intra-dct-only	0 (off)	Use only the DCT for intra blocks.
--use-inter-dct-only	0 (off)	Use only the DCT for inter blocks.
--use-intra-default-tx-only	0 (off)	Use only the default transform type of each intra mode.

Loop filters (3 options)

Option	Default	Description
--loopfilter-control	1 (all frames)	Deblocking filter: 0 off, 1 all frames, 2 skip non-reference frames, 3 skip low-motion frames.
--enable-cdef	0 (off)	CDEF, the constrained directional enhancement (deringing) filter: 0 off, 1 all frames, 2 reference frames only, 3 adaptive, which weakens it at high quality. Mainline enables it; turn it back on with 1 or 3 if ringing shows around edges at low bitrates.
--enable-restoration	1 (0 in realtime)	Loop restoration (Wiener and self-guided filters). It is slow to search and is always off in realtime mode. --tune-content=psy101 and --fast-decode=2 or higher turn it off.

Resize and super-resolution (8 options)

Option	Default	Description
--resize-mode	0 (off)	Code frames at a lower resolution while the render size keeps the original: 0 off, 1 fixed (--resize-denominator), 2 random (testing), 3 dynamic (realtime CBR).
--resize-denominator	8	Resize factor 8/N for non-key frames, N = 8–16 (16 halves both dimensions).
--resize-kf-denominator	8	Resize factor 8/N for keyframes, N = 8–16.
--superres-mode	0 (off)	Super-resolution: code frames at reduced width and let the decoder upscale them in-loop: 0 off, 1 fixed, 2 random, 3 above a quantiser threshold, 4 automatic.
--superres-denominator	8	Horizontal super-resolution factor 8/N for non-key frames, N = 8–16.
--superres-kf-denominator	8	Horizontal super-resolution factor 8/N for keyframes, N = 8–16.
--superres-qthresh	63	Mode 3: use super-resolution on non-key frames whose quantiser (1–63) exceeds this.
--superres-kf-qthresh	32	Mode 3: the same threshold for keyframes.

Film grain and denoising (5 options)

Option	Default	Description
--denoise-noise-level	0 (off)	Film-grain synthesis: estimate the source grain, denoise before encoding and signal grain for the decoder to add back. 0–50; keep it low (single digits to about 10) to avoid patterned grain.
--denoise-block-size	16	Block size in pixels for the grain estimator. Mainline defaults to 32.
--enable-dnl-denoising	1 (on)	Encode the denoised frame. With 0 the original frame is encoded and only the estimated grain parameters are added, which avoids the denoiser’s smearing. --help claims 0, but the default in normal builds is 1.
--film-grain-table	unset	Read film-grain parameters from a table file, such as a photon-noise table from Av1an or grav1synth, instead of estimating them.
--film-grain-test	0 (off)	Use one of libaom’s 16 built-in film-grain test parameter sets (1–16).

Entropy coding and cost updates (5 options)

Option	Default	Description
--cdf-update-mode	1	Adaptation of the entropy-coding probabilities (CDFs): 0 never, 1 every frame, 2 selectively.
--coeff-cost-upd-freq	0 (superblock)	How often the encoder refreshes its coefficient rate estimates: 0 each superblock, 1 each superblock row, 2 each tile, 3 never. Higher values are faster.
--mode-cost-upd-freq	0 (superblock)	Refresh interval for mode rate estimates, with the same values.
--mv-cost-upd-freq	0 (superblock)	Refresh interval for motion-vector rate estimates, with the same values.
--dv-cost-upd-freq	0 (superblock)	Refresh interval for intra-block-copy vector rate estimates, with the same values.

Signalling, levels and error resilience (12 options)

Option	Default	Description
--color-primaries	unspecified	Colour primaries (CICP) written to the sequence header; signalling only, no conversion. Values: bt709, unspecified, bt601, bt470m, bt470bg, smpte240, film, bt2020, xyz, smpte431, smpte432, ebu3213.
--transfer-characteristics	unspecified	Transfer characteristics (CICP), e.g. bt709, smpte2084 (PQ) or hlg. Values: unspecified, bt709, bt470m, bt470bg, bt601, smpte240, lin, log100, log100sq10, iec61966, bt1361, srgb, bt2020-10bit, bt2020-12bit, smpte2084, hlg, smpte428.
--matrix-coefficients	unspecified	Matrix coefficients (CICP). Values: identity, bt709, unspecified, fcc73, bt470bg, bt601, smpte240, ycgco, bt2020ncl, bt2020cl, smpte2085, chromncl, chromcl, ictcp, ipt-c2, ycgco-re, ycgco-ro.
--chroma-sample-position	unknown	4:2:0 chroma siting: unknown, vertical (left, as MPEG-2) or colocated (top-left, as BT.2020).
--timing-info	unspecified	Timing information in the sequence header: unspecified, constant (fixed frame rate) or model (decoder model; not with hidden frames or super-resolution).
--target-seq-level-idx	31 (unconstrained)	Target level per operating point, written ABxy: operating point AB, level index xy, where index = (major − 2) × 4 + minor (8 is level 4.0, 19 is 6.3). The encoder limits its decisions to meet it.
--strict-level-conformance	0 (off)	Stop with an error if the stream cannot meet --target-seq-level-idx.
--set-tier-mask	0 (Main)	Bit mask of operating points that use the High tier instead of Main (bit n is point n).
--full-still-picture-hdr	off	For single-frame encodes, write the full sequence header instead of the reduced still-picture header.
--error-resilient	0 (off)	Error-resilient frames, which stay decodable when references are lost. Range 0–1.
--global-error-resilient	0 (off)	Same effect as --error-resilient, set through the generic encoder configuration (the two are combined).
--frame-parallel	0 (off)	Disable backward probability adaptation so that a decoder can decode frames in parallel. Range 0–1. --fast-decode=3 turns it on.

Options added by aom-psy101 (8 options)

Option	Default	Description
--auto-tiling	3	Automatic tiling, 0–7 (0 off). Higher values allow smaller tiles: at least 32 superblocks per tile side at 1, down to 4 at 7 (halved with 128×128 superblocks). It fills in only tile columns and rows not set explicitly; values above 5 force 64×64 superblocks. With Av1an, set 0 to avoid tiles. Replaces mainline’s --auto-tiles.
--fast-decode	0 (off)	Easier decoding at some efficiency cost, 0–3: 1 caps the GF pyramid height at 4, 2 also disables loop restoration, 3 also enables frame-parallel decoding mode.
--luma-bias	0 (off)	0–15. Lowers the RD multiplier of dark blocks by a perceptual (PQ-slope) weight of their brightness, so shadows get more bits. Ignored for PQ (smpte2084) and log transfer characteristics.
--ssim-rd-mult	100	0–1000 (%). Scales the SSIM-based RD multiplier used by --tune=ssim, iq, ssimulacra2 and image_perceptual_quality.
--ssim-vmaf-rd	0	Share of SSIM RD, in percent (0–100), that replaces VMAF RD in the VMAF tunes. Requires a build with -DCONFIG_TUNE_VMAF=1.
--vmaf-rd-resize	1 (half)	Downscale for VMAF RD calculations: 0 full resolution, 1 half, 2 quarter, 3 eighth. Requires a build with -DCONFIG_TUNE_VMAF=1.
--vmaf-preprocessing	0 (off)	Force libaom’s VMAF preprocessing (sharpening) whatever the tune: 0 off, 1 block-based VMAF-NEG, 2 block-based, 3 frame-based. Requires a build with -DCONFIG_TUNE_VMAF=1.
--vmaf-quantization	0 (off)	Force the VMAF tunes’ quantiser adjustment whatever the tune. Range 0–1. Requires a build with -DCONFIG_TUNE_VMAF=1.