SVT-AV1 Parameters

June 5, 2026 · View on GitHub

SVT-AV1 Parameters

Configuration File Parameters

The encoder parameters are listed in this table below along with their status of support, command line parameter and the range of values that the parameters can take. Any of the parameters below that have a non-empty Configuration file parameter field, can be set by adding them to the Sample.cfg file.

Options

Configuration file parameter	Command line	Range	Default	Description
	--help			Shows the command line options currently available
	--color-help			Reproduces Appendix A.2 of the SVT-AV1 User Guide for AV1 metadata
	--version			Shows the version of the library that's linked to the library
InputFile	-i	any string	None	Input raw video (y4m and yuv) file path, use `stdin` or `-` to read from pipe
StreamFile	-b	any string	None	Output compressed file path, use `stdout` or `-` to write to pipe. Format is auto-detected from extension (`.ivf` or `.obu`), default is IVF
	--ivf			Output bitstream in IVF container format (default)
	--obu			Output bitstream as raw OBU (Open Bitstream Units) without IVF container
	-c	any string	None	Configuration file path
ErrorFile	--errlog	any string	`stderr`	Error file path
ReconFile	-o	any string	None	Reconstructed yuv file path
StatFile	--stat-file	any string	None	PSNR / SSIM per picture stat output file path, requires `--enable-stat-report 1`
Progress	--progress	[0-2]	1	Verbosity of the output [0: no progress is printed, 1: default output, 2: detailed output]
NoProgress	--no-progress	[0-1]	0	Do not print out progress [1: `--progress 0`, 0: `--progress 1`]
EncoderMode	--preset	[-1-13]	8	Encoder preset, presets < 0 are for debugging. Higher presets means faster encodes, but with a quality tradeoff
SvtAv1Params	--svtav1-params	any string	None	Colon-separated list of `key=value` pairs of parameters with keys based on command line options without `--`

Usage of SvtAv1Params

To use the --svtav1-params option, the syntax is --svtav1-params option1=value1:option2=value2....

An example is:

SvtAv1EncApp \
  -i input.y4m \
  -b output.ivf \
  --svtav1-params \
  "preset=10:crf=30:irefresh-type=kf:matrix-coefficients=bt709:mastering-display=G(0.2649,0.6900)B(0.1500,0.0600)R(0.6800,0.3200)WP(0.3127,0.3290)L(1000.0,1)"

This will set --preset to 10 and --crf to 30 inside the API along with some other parameters.

Do note however, that there is no error checking for duplicate keys and only for invalid keys or values.

For more information on valid values for specific keys, refer to the EbEncSettings file.

Encoder Global Options

Configuration file parameter	Command line	Range	Default	Description
SourceWidth	-w	[4-16384]	None	Frame width in pixels, inferred if y4m.
SourceHeight	-h	[4-8704]	None	Frame height in pixels, inferred if y4m.
ForcedMaximumFrameWidth	--forced-max-frame-width	[4-16384]	None	Maximum frame width value to force.
ForcedMaximumFrameheight	--forced-max-frame-height	[4-8704]	None	Maximum frame height value to force.
FrameToBeEncoded	-n	[0-`($2^{63}$)-1`]	0	Number of frames to encode. If `n` is larger than the input, the encoder will loop back and continue encoding
FrameToBeSkipped	--skip	[0-`($2^{63}$)-1`]	0	Number of frames to skip.
BufferedInput	--nb	[-1, 1-`($2^{31}$)-1`]	-1	Buffer `n` input frames into memory and use them to encode. Only buffered frames will be encoded.
EncoderColorFormat	--color-format	[0-3]	1	Color format, only yuv420 is supported at this time [0: yuv400, 1: yuv420, 2: yuv422, 3: yuv444]
Profile	--profile	[0-2]	0	Bitstream profile [0: main, 1: high, 2: professional]
Level	--level	[0,2.0-7.3]	0	Bitstream level, defined in A.3 of the av1 spec [0: auto]
FrameRateNumerator	--fps-num	[0- $2^{32}$ -1]	60000	Input video frame rate numerator
FrameRateDenominator	--fps-denom	[0- $2^{32}$ -1]	1000	Input video frame rate denominator
EncoderBitDepth	--input-depth	[8, 10]	8	Input video file and output bitstream bit-depth
Injector	--inj	[0-1]	0	Inject pictures to the library at defined frame rate
InjectorFrameRate	--inj-frm-rt	[0-240]	60	Set injector frame rate, only applicable with `--inj 1`
StatReport	--enable-stat-report	[0-1]	0	Calculates and outputs PSNR SSIM metrics at the end of encoding
Asm	--asm	[0-11, c-max]	max	Limit assembly instruction set [c, mmx, sse, sse2, sse3, ssse3, sse4_1, sse4_2, avx, avx2, avx512, avx512icl, max] for x86 platforms, [c, neon, crc32, neon_dotprod, neon_i8mm, sve, sve2] for Arm platforms.
LevelOfParallelism	--lp	[0, 6]	0	Controls the number of threads to create and the number of picture buffers to allocate (higher level means more parallelism). 0 means choose level based on machine core count. Refer to Appendix A.1
FastDecode	--fast-decode	[0,2]	0	Tune settings to output bitstreams that can be decoded faster, [0 = OFF, 1,2 = levels for decode-targeted optimization (2 yields faster decoder speed)]. Defaults to 5 temporal layers structure but may override with --hierarchical-levels
Tune	--tune	[0-5]	1	Optimize the encoding process for different desired outcomes [0 = VQ (video and still image), 1 = PSNR (video and still image), 2 = SSIM (video and still image), 3 = IQ (still image only), 4 = MS-SSIM (video and still image), 5 = VMAF (video only)]
AdaptiveFilmGrain	--adaptive-film-grain	[0,1]	1	Allows film grain synthesis to be sourced from different block sizes depending on resolution
MaxTxSize	--max-tx-size	[32,64]	64	Restricts use of block transform sizes to the specified value

Rate Control Options

Configuration file parameter	Command line	Range	Default	Description
RateControlMode	--rc	[0-2]	0	Rate control mode [0: CRF or CQP (if `--aq-mode` is 0) [Default], 1: VBR, 2: CBR]
QP	--qp	[1-63]	35	Initial QP level value
CRF	--crf	[1-70]	35	Constant Rate Factor value, setting this value is similar to `--rc 0 --aq-mode 2 --qp x`. Compared to `--qp`, `--crf` can take a value up to 70, and can be set in 0.25 increments
CQP	--cqp	[1-70]	35	Constant Quality value, setting this value is similar to `--rc 0 --aq-mode 0 --qp x`. Compared to `--qp`, `--cqp` can take a value up to 70, and can be set in 0.25 increments
TargetBitRate	--tbr	[1-100000]	2000	Target Bitrate (kbps), only applicable for VBR and CBR encoding, also accepts `b`, `k`, and `m` suffixes
MaxBitRate	--mbr	[1-100000]	0	Maximum Bitrate (kbps) only applicable for CRF encoding, also accepts `b`, `k`, and `m` suffixes
UseQpFile	--use-q-file	[0-1]	0	Overwrite the encoder default picture based QP assignments and use QP values from `--qp-file`
QpFile	--qpfile	any string	Null	Path to a file containing per picture QP value
MaxQpAllowed	--max-qp	[0-63]	63	Maximum quantizer (lowest quality)
MinQpAllowed	--min-qp	[0-63]	0	Minimum quantizer (highest quality)
EnableVarianceBoost	--enable-variance-boost	[0-1]	0	Enable Variance Boost
VarianceBoostStrength	--variance-boost-strength	[1-4]	2	Set variance curve strength for Variance Boost feature [1: mild, 2: gentle [Default], 3: medium, 4: aggressive]
VarianceOctile	--variance-octile	[1-8]	5	Set variance algorithm 8x8 block selectivity level [1: 1st octile, 4: median, 5: 5th octile [Default], 8: maximum]
AdaptiveQuantization	--aq-mode	[0-2]	2	Set adaptive QP level [0: off, 1: variance base using AV1 segments, 2: deltaq pred efficiency]
HBDMDS	--hbd-mds	[-1-2]	-1	Activation of high bit depth mode decisions; 10-bit MD only works with 10-bit inputs (-1: default preset behavior, 0: full 8b MD 1: full 10b MD, 2: hybrid 8/10b MD)
QpScaleCompressStrength	--qp-scale-compress-strength	[0-3]	0	Sets the strength the QP scale algorithm compresses values across all temporal layers, which results in more consistent video quality (less quality variation across frames in a mini-gop)
AcBias	--ac-bias	[0.0-8.0]	0.0	Sets the strength of the internal RD metric to bias toward high-frequency error (helps with texture preservation and film grain retention)
UseFixedQIndexOffsets	--use-fixed-qindex-offsets	[0-2]	0	Overwrite the encoder default hierarchical layer based QP assignment and use fixed Q index offsets
KeyFrameQIndexOffset	--key-frame-qindex-offset	[-64-63]	0	Overwrite the encoder default keyframe Q index assignment
KeyFrameChromaQIndexOffset	--key-frame-chroma-qindex-offset	[-64-63]	0	Overwrite the encoder default chroma keyframe Q index assignment
LumaYDCQindexOffset	--luma-y-dc-qindex-offset	[-64-63]	0	Overwrite the encoder default dc Q index offset for luma plane
ChromaUDCQindexOffset	--chroma-u-dc-qindex-offset	[-64-63]	0	Overwrite the encoder default dc Q index offset for chroma Cb plane
ChromaUACQindexOffset	--chroma-u-ac-qindex-offset	[-64-63]	0	Overwrite the encoder default ac Q index offset for chroma Cb plane
ChromaVDCQindexOffset	--chroma-v-dc-qindex-offset	[-64-63]	0	Overwrite the encoder default dc Q index offset for chroma Cr plane
ChromaVACQindexOffset	--chroma-v-ac-qindex-offset	[-64-63]	0	Overwrite the encoder default ac Q index offset for chroma Cr plane
QIndexOffsets	--qindex-offsets	any string	`0,0,..,0`	list of luma Q index offsets per hierarchical layer, separated by `,` with each offset in the range of [-64-63]
ChromaQIndexOffsets	--chroma-qindex-offsets	any string	`0,0,..,0`	list of chroma Q index offsets per hierarchical layer, separated by `,` with each offset in the range of [-64-63]
StartupGopQpOffset	--startup-qp-offset	[-63-63]	0	Start-up GOP QP offset; will be added to the sequence-QP before deriving the picture-QP
UnderShootPct	--undershoot-pct	[0-100]	25, 50	Allowable datarate undershoot (min) target (%), default depends on the rate control mode (25 for CBR, 50 for VBR)
OverShootPct	--overshoot-pct	[0-100]	25	Allowable datarate overshoot (max) target (%), default depends on the rate control mode
MbrOverShootPct	--mbr-overshoot-pct	[0-100]	50	Allowable datarate overshoot (max) target (%), Only applicable for Capped CRF
BufSz	--buf-sz	[20-10000]	1000	Client maximum buffer size (ms), only applicable for CBR
BufInitialSz	--buf-initial-sz	[20-10000]	600	Client initial buffer size (ms), only applicable for CBR
BufOptimalSz	--buf-optimal-sz	[20-10000]	600	Client optimal buffer size (ms), only applicable for CBR
RecodeLoop	--recode-loop	[0-4]	4	Recode loop level, look at the "Recode loop level table" in the user's guide for more info [0: off, 4: preset based]
MinSectionPct	--minsection-pct	[0-100]	0	GOP min bitrate (expressed as a percentage of the target rate)
MaxSectionPct	--maxsection-pct	[0-10000]	2000	GOP max bitrate (expressed as a percentage of the target rate)
GopConstraintRc	--gop-constraint-rc	[0-1]	0	Constrains the rate control to match the target rate for each GoP [0 = OFF, 1 = ON]
EnableQM	--enable-qm	[0-1]	0	Enable quantisation matrices
MinQmLevel	--qm-min	[0-15]	8	Min quant matrix flatness
MaxQmLevel	--qm-max	[0-15]	15	Max quant matrix flatness
MinChromaQmLevel	--chroma-qm-min	[0-15]	8	Min chroma quant matrix flatness
MaxChromaQmLevel	--chroma-qm-max	[0-15]	15	Max chroma quant matrix flatness
LambdaScaleFactors	--lambda-scale-factors	[0- ]	'128,.,128'	list of scale factors for lambda values used for different SvtAv1FrameUpdateType, separated by `,` divide by 128 is the actual scale factor in float
RoiMapFile	--roi-map-file	any string	Null	Path to a file containing picture based QP offset map
TemporalFilteringStrength	--tf-strength	[0-4]	3	Manually adjust temporal filtering strength. Higher values = stronger temporal filtering
LuminanceQpBias	--luminance-qp-bias	[0-100]	0	Adjusts a frame's QP based on its average luma value
Sharpness	--sharpness	[-7-7]	0	Bias towards decreased/increased sharpness

UseFixedQIndexOffsets and more information

UseFixedQIndexOffsets and its associated arguments (HierarchicalLevels, QIndexOffsets, ChromaQIndexOffsets, KeyFrameQIndexOffset, KeyFrameChromaQIndexOffset) are used together to specify the qindex offsets based on frame type and temporal layer when rc is set to 0.

QP value specified by the --qp argument is assigned to the pictures at the highest temporal layer. It is first converted to a qindex, then the corresponding qindex offsets are added on top of it based on the frame types (Key/Inter) and temporal layer id.

Qindex offset can be negative. The final qindex value will be clamped within the valid min/max qindex range.

For chroma plane, after deciding the qindex for the luma plane, the corresponding chroma qindex offsets are added on top of the luma plane qindex based on frame types and temporal layer id.

--qindex-offsets and --chroma-qindex-offsets have to be used after the --hierarchical-levels parameter. The number of qindex offsets should be HierarchicalLevels plus 1, and they can be enclosed in [] to separate the list.

An example command line is:

SvtAv1EncApp -i in.y4m -b out.ivf --rc 0 -q 42 --hierarchical-levels 3 --use-fixed-qindex-offsets 1 --qindex-offsets [-12,-8,-4,0] --key-frame-qindex-offset -20 --key-frame-chroma-qindex-offset -6 --chroma-qindex-offsets [-6,0,12,24]

For this command line, corresponding qindex values are:

Frame Type	Luma qindex	Chroma qindex
Key Frame	148 (42x4 - 20)	142 (148 - 6)
Layer0 Frame	156 (42x4 - 12)	150 (156 - 6)
Layer1 Frame	160 (42x4 - 8)	160 (160 + 0)
Layer2 Frame	164 (42x4 - 4)	176 (164 + 12)
Layer3 Frame	168 (42x4 + 0)	192 (168 + 24)

EnableQM and more information

With EnableQM, MinQmLevel and MaxQmLevel, user can customize the quantization matrix used in luma quantization procedure (MinChromaQmLevel & MaxChromaQmLevel for chroma control) instead of using the default one. With the default quantization matrix, all coefficients share the same weight, whereas with non-default ones, coefficients can have different weight throughMore actions the settings made by users. The deviation of weight (or flatness, equivalently) is controlled by arguments MinQmLevel and MaxQmLevel. There are sixteen quantization matrix levels, ranging from level 0 to level 15. The lower the level is the larger deviation of weight the quantization matrix will provide. Level 15 is fully flat in weight and is set as the default quantization matrix. A lower level quantization matrix typically results in bitstreams with lower bitrate and slightly worse quality in CRF rate control mode. The reduction in bitrate is more obvious with low CRF than high CRF.

The quantization matrices feature signals at frame level. When the feature is enabled, the encoder decides each frame’s quantization matrix level by normalizing its qindex to user specified quantization matrix level range (from MinQmLevel to MaxQmLevel).

An example command line is:

SvtAv1EncApp -i in.y4m -b out.ivf --keyint -1 --enable-qm 1 --qm-min 0 --qm-max 15

Another example with chroma QM min/max specified:

SvtAv1EncApp -i in.y4m -b out.ivf --keyint -1 --enable-qm 1 --qm-min 0 --qm-max 15 --chroma-qm-min 4 --chroma-qm-max 8

Recode loop level table

level	description
0	Off
1	Allow recode for KF and exceeding maximum frame bandwidth
2	Allow recode only for key frames, alternate reference frames, and Golden frames
3	Allow recode for all frame types based on bitrate constraints
4	Preset based decision

RoiMapFile and QP Offset Map file format

In some applications such as AR / VR, identifying the ROI (Region Of Interest) helps the encoder focus the bit usage where it's needed. This is realized by allowing applications to pass a picture based ROI map to the encoder.

The QP Offset Map file contains one or more picture based QP offset maps. Every line consists of a frame number and the QP offsets for each 64x64 block set in a row-by-row order. Below is an example ROI map file for a 352x288 content:

0 12 -32 -32 -32 -32 -32 12 -32 -32 -32 -32 -32 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16

The encoder uses alternate quantizer segment feature to set block level qindex and uses alternate loop filter segment feature to set loop filter strength level. When both AQ mode 1 (variance base adaptive QP) and ROI are enabled, segment QP is decided by ROI map instead of by variance.

An example command line is:

SvtAv1EncApp -i in.y4m -b out.ivf --roi-map-file roi_map.txt

Multi-pass Options

Configuration file parameter	Command line	Range	Default	Description
Pass	--pass	[0-2]	0	Multi-pass selection [0: single pass encode, 1: first pass, 2: second pass]
Stats	--stats	any string	"svtav1_2pass.log"	Filename for multi-pass encoding
Passes	--passes	[1-2]	1	Number of encoding passes, default is preset dependent [1: one pass encode, 2: multi-pass encode]

Pass information

Pass	Stats io
0	""
1	"w"
2	"r"

--pass 2 is only available for non-crf modes and all passes except single-pass requires the --stats parameter to point to a valid path

GOP size and type Options

Configuration file parameter	Command line	Range	Default	Description
Keyint	--keyint	[-2-`($2^{31}$)-1`]	-2	GOP size (frames), use `s` suffix for seconds (SvtAv1EncApp only) [-2: ~5 seconds, -1: "infinite" only for CRF, 0: == -1]
IntraRefreshType	--irefresh-type	[1-2]	2	Intra refresh type [1: FWD Frame (Open GOP), 2: KEY Frame (Closed GOP)]
SceneChangeDetection	--scd	[0-1]	0	Scene change detection control
Lookahead	--lookahead	[-1,0-120]	-1	Number of frames in the future to look ahead, beyond minigop, temporal filtering, and rate control [-1: auto]
HierarchicalLevels	--hierarchical-levels	[0-5]	<=M12:5 , else: 4	Set hierarchical levels beyond the base layer [0: flat, 1: 2 temporal layers, 2: 3 temporal layers, 3: 4 temporal layers, 5: 6 temporal layers]
PredStructure	--pred-struct	[0-2]	2	Set prediction structure [0: all intra, 1: low delay, 2: random access]
ForceKeyFrames	--force-key-frames	any string	None	Force key frames at the comma separated specifiers. `#f` for frames, `#.#s` for seconds
EnableDg	--enable-dg	[0-1]	1	Enable Dynamic GoP. The algorithm changes the hierarchical structure based on the content
StartupMgSize	--startup-mg-size	[0, 2, 3, 4]	0	Specify another mini-gop configuration for the first mini-gop after the key-frame [0: OFF, 2: 3 temporal layers, 3: 4 temporal layers, 4: 5 temporal layers]
RealTime	--rtc	[0-1]	0	Enables fast settings for real-time communication when using low-delay mode. Forces low-delay pred struct to be used.

AV1 Specific Options

Configuration file parameter	Command line	Range	Default	Description
TileRow	--tile-rows	[0-6]	0	Number of tile rows to use, `TileRow == log2(x)`, default changes per resolution
TileCol	--tile-columns	[0-4]	0	Number of tile columns to use, `TileCol == log2(x)`, default changes per resolution
LoopFilterEnable	--enable-dlf	[0-2]	1	Deblocking loop filter control (1: enabled, 2: slower, more accurate filtering)
CDEFLevel	--enable-cdef	[0-1]	1	Enable Constrained Directional Enhancement Filter
EnableRestoration	--enable-restoration	[0-1]	1	Enable loop restoration filter
Mfmv	--enable-mfmv	[-1-1]	-1	Motion Field Motion Vector control [-1: auto]
EnableTF	--enable-tf	[0-2]	1	Enable ALT-REF (temporally filtered) frames [0: off, 1: on, 2: adaptive]
EnableTfKey	--enable-kf-tf	[0-1]	1	Enable MCTF for key frames [0: off, 1: on]
EnableOverlays	--enable-overlays	[0-1]	0	Enable the insertion of overlayer pictures which will be used as an additional reference frame for the base layer picture
ScreenContentMode	--scm	[0-3]	2	Set screen content detection level [0: None, 1: Block Copy + Palette, 2: content adaptive, 3: content adaptive (anti-alias aware)]
EnableIntraBC	--enable-intrabc	[0-1]	1	Enable Intra Block Copy [0: off, 1: on (preset-based)]
FilmGrain	--film-grain	[0-50]	0	Enable film grain [0: off, 1-50: level of denoising for film grain]
FilmGrainDenoise	--film-grain-denoise	[0-1]	0	Apply denoising when film grain is ON, default is 0 [0: no denoising, film grain data sent in frame header, 1: level of denoising is set by the film-grain parameter]
FGSTable	--fgs-table	any string	None	Path to a file containing a pre-generated film grain table for grain synthesis, only available through SvtAv1Enc interface
SuperresMode	--superres-mode	[0-4]	0	Enable super-resolution mode, refer to the super-resolution section below for more info
SuperresDenom	--superres-denom	[8-16]	8	Super-resolution denominator, only applicable for mode == 1 [8: no scaling, 16: half-scaling]
SuperresKfDenom	--superres-kf-denom	[8-16]	8	Super-resolution denominator for key frames, only applicable for mode == 1 [8: no scaling, 16: half-scaling]
SuperresQthres	--superres-qthres	[0-63]	43	Super-resolution q-threshold, only applicable for mode == 3
SuperresKfQthres	--superres-kf-qthres	[0-63]	43	Super-resolution q-threshold for key frames, only applicable for mode == 3
SframeInterval	--sframe-dist	[0-`($2^{31}$)-1`]	0	S-Frame interval (frames) [0: OFF, > 0: ON]
SframeMode	--sframe-mode	[1-4]	2	S-Frame insertion mode [1: the considered frame will be made into an S-Frame only if it is an altref frame, 2: the next altref frame will be made into an S-Frame， 3: adjust minigop size to make an S-Frame at specific position, 4. adjust minigop size to make an S-Frame inserting at specific position in decode order]
SframePositions	--sframe-posi	any string	None	S-Frame insertion positions, a list separated by ',', S-Frame process inserts by the specified frame numbers (0 based), only applicable for mode 3 and mode 4
SframeQPs	--sframe-qp	any string	None	S-Frame setup QP, a list separated by ',', QP value(s) set with S-Frame insertion, with each QP in the range of [1-63]. If only one QP value is set, this QP is applied to all S-Frames
SframeQPOffsets	--sframe-qp-offset	any string	None	S-Frame setup QP offset, a list separated by ',', QP offset value(s) set with S-Frame insertion, with each QP offset value in the range of [-63-63]. If only one QP offset value is set, this QP offset is applied to all S-Frames
ResizeMode	--resize-mode	[0-4]	0	Enable reference scaling mode
ResizeDenom	--resize-denom	[8-16]	8	Reference scaling denominator, only applicable for mode == 1 [8: no scaling, 16: half-scaling]
ResizeKfDenom	--resize-kf-denom	[8-16]	8	Reference scaling denominator for key frames, only applicable for mode == 1 [8: no scaling, 16: half-scaling]
ResizeFrameEvents	--frame-resz-events	any string	None	Frame scale events, in a list separated by ',', scaling process starts from the given frame number (0 based) with new denominators, only applicable for mode == 4
ResizeFrameKfDenoms	--frame-resz-kf-denoms	[8-16]	8	Frame scale denominator for key frames in event, in a list separated by ',', only applicable for mode == 4
ResizeFrameDenoms	--frame-resz-denoms	[8-16]	8	Frame scale denominator in event, in a list separated by ',', only applicable for mode == 4
Avif	--avif	[0-1]	0	Enable still-picture coding optimizations for improved coding efficiency and reduced memory usage

Super-Resolution

Super resolution is better described in the Super-Resolution documentation, but this basically allows the input to be encoded at a lower resolution, horizontally, but then later upscaled back to the original resolution by the decoder.

SuperresMode	Value
0	None, no frame super-resolution allowed
1	All frames are encoded at the specified scale of 8/`denom`, thus a `denom` of 8 means no scaling, and 16 means half-scaling
2	All frames are coded at a random scale
3	Super-resolution scale for a frame is determined based on the q_index, a qthreshold of 63 means no scaling
4	Automatically select the super-resolution mode for appropriate frames

The performance of the encoder will be affected for all modes other than mode 0. And for mode 4, it should be noted that the encoder will run at least twice, one for down scaling, and another with no scaling, and then it will choose the best one for each of the appropriate frames.

For more information on the decision-making process, please look at section 2.2 of the super-resolution doc

Reference Scaling

Reference Scaling is better described in the reference scaling documentation, but this basically allows the input to be encoded and the output at a lower resolution, scaling ratio applys on both horizontally and vertically.

ResizeMode	Value
0	None, no frame resize allowed
1	Fixed mode, all frames are encoded at the specified scale of 8/`denom`, thus a `denom` of 8 means no scaling, and 16 means half-scaling
2	Random mode, all frames are coded at a random scale, the scaling `denom` can be picked from 8 to 16
3	Dynamic mode, scale for a frame is determined based on buffer level and average qp in rate control, scaling ratio can be 3/4 or 1/2. This mode can only work in 1-pass CBR low-delay mode
4	Random access mode, scaling is controlled by scale events, which determine scaling in a specified scaling `denom` or recover to original resolution

Example CLI of reference scaling dynamic mode:

-i input.yuv -b output.ivf --resize-mode 3 --rc 2 --pred-struct 1 --tbr 1000

Example CLI of reference scaling random access mode:

-i input.yuv -b output.ivf --resize-mode 4 --frame-resz-events 5,10,15,20,25,30 --frame-resz-kf-denoms 8,9,10,11,12,13 --frame-resz-denoms 16,15,14,13,12,11 --frame-resz-events, --frame-resz-kf-denoms and --frame-resz-denoms shall be all set in same amount of parameters in list

Updating Encoding Parameters During the Encoding Sessions

The --force-key-frames option is meant to allow the non-uniform placement of key frames within the stream. While this option is currently supported only for the CRF mode via the commandline, using it within the CBR mode can be achieved by passing the command of inserting a keyframe through the API field EbAv1PictureType pic_type; in the EbBufferHeaderType structure. A sample programming usage of this option can be found in the sample application file EbAppProcessCmd.c tracking the FTR_KF_ON_FLY_SAMPLE macro defined in EbDebugMacros.h. Similarly by setting the field uint32_t qp; in the EbBufferHeaderType structure at a key frame placement, the encoder will update the sequence QP or CRF level according to the newly defined level (only applicable to CRF mode).

Other options such as updating the Bitrate and resolution during the encoding sessions have been added to the API (starting v1.8.0) by using the abstract structure EbPrivDataNode and a programming sample showing its usage can be found by tracking the marcos FTR_RATE_ON_FLY_SAMPLE and FTR_RES_ON_FLY_SAMPLE respectively. In the case of a resolution update request, please note that the encoder library will assume the upscaling and downscaling to have been performed prior to passing the frames.

Color Description Options

Configuration file parameter	Command line	Range	Default	Description
ColorPrimaries	--color-primaries	[0-12, 22]	2	Color primaries, refer to the user guide Appendix A.2 for full details
TransferCharacteristics	--transfer-characteristics	[0-22]	2	Transfer characteristics, refer to the user guide Appendix A.2 for full details
MatrixCoefficients	--matrix-coefficients	[0-14]	2	Matrix coefficients, refer to the user guide Appendix A.2 for full details
ColorRange	--color-range	[0-1]	0	Color range [0: Studio, 1: Full]
ChromaSamplePosition	--chroma-sample-position	any string	unknown	Chroma sample position ['unknown', 'vertical'/'left', 'colocated'/'topleft']
MasteringDisplay	--mastering-display	any string	none	Mastering display metadata in the format of "G(x,y)B(x,y)R(x,y)WP(x,y)L(max,min)", refer to the user guide Appendix A.2 for full details
ContentLightLevel	--content-light	any string	none	Set content light level in the format of "max_cll,max_fall", refer to the user guide Appendix A.2 for full details

Appendix A Encoder Parameters

1. Thread management parameters

LevelOfParallelism (previously LogicalProcessors, which was deprecated in v3.0 and replaced with LevelOfParallelism) is used to specify how much parallelism is desired; higher levels will create more threads and process more pictures in parallel, leading to greater fps but larger memory use. If LevelOfParallelism is not set, the amount of parallelism (threads/memory) will be decided by the encoder based on the machine's core count.

SvtAv1EncApp.exe -i in.yuv -w 3840 -h 2160 --lp 4

The --lp level does not indicate the number of threads targeted, nor does it constrain the encoder to run on a certain number of logical processors. The number of threads created and memory used is determined by settings in the code (see load_default_buffer_configuration_settings).

Parallelism is achieved in two ways:

By creating new threads to process pictures and sub-picture blocks (e.g. superblocks) in parallel.
By increasing the number of pictures in the pipeline, which can then be processed concurrently.

Higher LevelOfParallelism will increase both the threads and pictures in a way that optimizes speed and memory at each level. In CRF mode, levels 4 and higher will process extra mini-gops in parallel as well, leading to higher speed, but much higher memory. In low-delay mode, only one picture can be processed at once, so no extra pictures will be allocated.

The --pin option allows the user to pin the execution to a specific number of cores, specifically, the first N cores, where N is the value passed with --pin. If '--lp' is not specified, the default parallelism will be based on the N cores available for the process to run, rather than all the cores on the machine. If '--lp' is specified, that level of parallelism will be used, regardless of N.

To set cpu affinity a cpu affinity utility such as taskset or numactl to control could be used to pin execution to desired threads.

Example:

taskset --cpu-list 0-3 ./SvtAv1EncApp --preset 4 -q 32 --keyint 200 -i input1.y4m -b svt_1.bin --lp 3 taskset --cpu-list 4-7 ./SvtAv1EncApp --preset 4 -q 32 --keyint 200 -i input2.y4m -b svt_2.bin --lp 3

This example will ensure that the first encode will run on the first 4 cores and the second encode will run on the second 4 cores. In this example, if CPU utilization is not saturated for --lp 3 for these cores, higher levels of --lp could be employed for more parallelism with a memory usage increase.

2. AV1 metadata

Please see the subsection 6.4.2, 6.7.3, and 6.7.4 of the AV1 Bitstream & Decoding Process Specification for more details on some expected values.

The available options for ColorPrimaries (--color-primaries) are:

1: bt709, BT.709
2: unspecified, default
4: bt470m, BT.470 System M (historical)
5: bt470bg, BT.470 System B, G (historical)
6: bt601, BT.601
7: smpte240, SMPTE 240
8: film, Generic film (color filters using illuminant C)
9: bt2020, BT.2020, BT.2100
10: xyz, SMPTE 428 (CIE 1921 XYZ)
11: smpte431, SMPTE RP 431-2
12: smpte432, SMPTE EG 432-1
22: ebu3213, EBU Tech. 3213-E

The available options for TransferCharacteristics (--transfer-characteristics) are:

1: bt709, BT.709
2: unspecified, default
4: bt470m, BT.470 System M (historical)
5: bt470bg, BT.470 System B, G (historical)
6: bt601, BT.601
7: smpte240, SMPTE 240 M
8: linear, Linear
9: log100, Logarithmic (100 : 1 range)
10: log100-sqrt10, Logarithmic (100 * Sqrt(10) : 1 range)
11: iec61966, IEC 61966-2-4
12: bt1361, BT.1361
13: srgb, sRGB or sYCC
14: bt2020-10, BT.2020 10-bit systems
15: bt2020-12, BT.2020 12-bit systems
16: smpte2084, SMPTE ST 2084, ITU BT.2100 PQ
17: smpte428, SMPTE ST 428
18: hlg, BT.2100 HLG, ARIB STD-B67

The available options for MatrixCoefficients (--matrix-coefficients) are:

0: identity, Identity matrix
1: bt709, BT.709
2: unspecified, default
4: fcc, US FCC 73.628
5: bt470bg, BT.470 System B, G (historical)
6: bt601, BT.601
7: smpte240, SMPTE 240 M
8: ycgco, YCgCo
9: bt2020-ncl, BT.2020 non-constant luminance, BT.2100 YCbCr
10: bt2020-cl, BT.2020 constant luminance
11: smpte2085, SMPTE ST 2085 YDzDx
12: chroma-ncl, Chromaticity-derived non-constant luminance
13: chroma-cl, Chromaticity-derived constant luminance
14: ictcp, BT.2100 ICtCp

The available options for ColorRange (--color-range) are:

0: studio, default
1: full

The available options for ChromaSamplePosition (--chroma-sample-position) are:

0: unknown, default
1: vertical/left, horizontally co-located with luma samples, vertical position in the middle between two luma samples
2: colocated/topleft, co-located with luma samples

MasteringDisplay (--mastering-display) and ContentLightLevel (--content-light) parameters are used to set the mastering display and content light level in the AV1 bitstream.

MasteringDisplay takes the format of G(x,y)B(x,y)R(x,y)WP(x,y)L(max,min) where

G(x,y) is the green channel of the mastering display
B(x,y) is the blue channel of the mastering display
R(x,y) is the red channel of the mastering display
WP(x,y) is the white point of the mastering display
L(max,min) is the light level of the mastering display

The x and y values can be coordinates from 0.0 to 1.0, as specified in CIE 1931 while the min,max values can be floating point values representing candelas per square meter, or nits. For the max,min values, they are generally specified in the range of 0.0 to 1.0, but there are no constraints on the provided values. Invalid values will be clipped accordingly.

ContentLightLevel takes the format of max_cll,max_fall where both values are integers clipped into a range of 0 to 65535.

Examples:

SvtAv1EncApp -i in.y4m -b out.ivf \
    --mastering-display "G(0.2649,0.6900)B(0.1500,0.0600)R(0.6800,0.3200)WP(0.3127,0.3290)L(1000.0,1)" \
    --content-light 100,50 \
    --color-primaries bt2020 \
    --transfer-characteristics smpte2084 \
    --matrix-coefficients bt2020-ncl \
    --chroma-sample-position topleft
    # Color primary is BT.2020, BT.2100
    # Transfer characteristic is SMPTE ST 2084, ITU BT.2100 PQ
    # matrix coefficients is BT.2020 non-constant luminance, BT.2100 YCbCr

# or

ffmpeg -y -i in.mp4 \
  -strict -2 \
  -c:a opus \
  -c:v libsvtav1 \
  -color_primaries:v bt2020 \
  -color_trc:v smpte2084 \
  -color_range:v pc \
  -chroma_sample_location:v topleft \
  -svtav1-params \
    "mastering-display=G(0.2649,0.6900)B(0.1500,0.0600)R(0.6800,0.3200)WP(0.3127,0.3290)L(1000.0,1):\
    content-light=100,50:\
    matrix-coefficients=bt2020-ncl:\
    chroma-sample-position=topleft" \
  out.mp4
# chroma-sample-position needs to be repeated because it currently isn't set ffmpeg's side

Appendix B Psychovisual Parameters

`--max-tx-size [32,64]`

--max-tx-size allows the encoder to restrict selection of blocks transform sizes up to a maximum size. Valid values are 32 and 64. In the AV1 standard, 64-pt transforms have the last 32 highest-frequency coefficients zeroed out during encoding, which means coded blocks can look visually blurry, especially when encoding fine noise-like textures. PSNR and SSIM-based RDO metrics don't seem to detect this blurriness, so this setting combats this issue by not allowing 64-pt transforms to be considered in the first place. The result is an overall increase in output quality consistency, especially for still images in the medium to high quality range.

`--qp-scale-compress-strength [0-3]`

--qp-scale-compress-strength is meant to improve spatio-temporal quality and by design, overall quality consistency. Of course, you trade off mean (average quality) to stddev (consistency). The stronger the algorithm strength, the more consistent quality is from keyframe to reference/bidirectional reference frames and other frame types. In exchange however, the fewer the opportunities frames can be used as references because they're relatively lower quality than the child frames. Thus, it brings down average performance in most cases (except for one case described further below). This parameter allows advanced users to switch between four levels of quantizer compression, compressing quantizer values across all hierarchical/temporal layers inside of a mini GOP.

0 disables the feature, the default value.
1 is --qp-scale-compress-strength, conservatively reducing the QP range used by the encoder. Useful for increasing visual consistency at almost all quality levels with next to no cost.
2 is --qp-scale-compress-strength, reducing the QP range used by the encoder further. This is useful at higher quality levels where restricting the QP range across layers is more important.
3 is --qp-scale-compress-strength, is the upper limit that was found useful for general-purpose (not Target Quality) encoding. This is useful at maximum fidelity expectations or when the set CRF/QP is very low. In the latter scenario, the feature can actually improve fidelity.

`--adaptive-film-grain [0,1]`

When enabled, the --adaptive-film-grain parameter adaptively varies the film grain blocksize based on the resolution of the input video. This often greatly improves the consistency of film grain in the output video, reducing grain patterns. Adaptive film grain is enabled by default.

`--tf-strength [0-4]`

--tf-strength is a parameter that allows users to configure the strength of temporal filtering on alternate reference frames, with an offset for keyframes if using Tune 0 (VQ). Based on the material, this can be perceptually salient.

`--enable-tf 2`

--enable-tf 2 enables experimental adaptive TF strength modulation based on 64x64 block error. This is not always perceptually or metrically salient, but it should provide feature parity with aomenc.

`--ac-bias [0.0-8.0]`

--ac-bias is an energy-preserving psycho-visual metric that helps increase subjective quality of video. This metric is based on the difference of the "energy" (SATD - SAD) of the source and reconstituted encoded blocks, similar to x264 and x265's implementation. Alternatively, a more lightweight rate adjustment mechanism based on total block "energy" (sum of transformed AC block coefficients) used by the Fast-PD0 and Fast-PD1 code paths is provided.

Moderate values (1.0-1.5) help retain sharpness and acuity of textures and scenes with complex motion.
High values (4.0-6.0, together with disabling temporal filtering and CDEF) can dramatically improve film grain and noise retention.

`--luminance-qp-bias [0-100]`

When enabled, the --luminance-qp-bias parameter enables frame-level luma bias to improve quality in dark scenes by adjusting frame-level QP based on average luminance across each frame.

`--sharpness [-7-7]`

The --sharpness parameter allows users to manually configure deblocking loop filter sharpness, and it also affects rate control. It is used in Tune 3 (IQ) and Tune 4 (MS_SSIM), which is designed for still image compression; that being said, it still may be useful for perceptual fidelity in video. By default, sharpness is set to 0.