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4 December 2025

20 days ago by ReadMe API

New parameters for SVT-AV1 encoder

Added new video codec parameters for the SVT-AV1 encoder:

Rate Control Parameters

ParameterDescriptionAllowed Values
crfConstant Rate Factor value (CRF mode)Integer between 1 and 63
mbrMaximum Bitrate for Capped CRFInteger 1-100000 (kbps), supports b/k/m suffixes
mbr-overshoot-pctAllowable datarate overshoot percentage for Capped CRFInteger 0-100
gop-constraint-rcEnable GoP constraint rate control0 – off
1 – on
buf-szClient buffer size in ms (CBR only)Integer 20-10000
buf-initial-szClient initial buffer size in ms (CBR only)Integer 20-10000
buf-optimal-szClient optimal buffer size in ms (CBR only)Integer 20-10000
minsection-pctGOP min bitrate (percentage of target rate)Integer 0-100
maxsection-pctGOP max bitrate (percentage of target rate)Integer 0-10000

Quantization Matrix Parameters

ParameterDescriptionAllowed Values
enable-qmEnable quantisation matrices0 – off
1 – on
qm-minMin quant matrix flatnessInteger 0-15
qm-maxMax quant matrix flatnessInteger 0-15
chroma-qm-minMin chroma quant matrix flatnessInteger 0-15
chroma-qm-maxMax chroma quant matrix flatnessInteger 0-15
lambda-scale-factorsScale factors for lambda values per frame type (comma-separated)Comma-separated integers (value/128 = actual scale)

Psychovisual (PSY) Parameters

ParameterDescriptionAllowed Values
tf-strengthTemporal filtering strengthInteger 0-4
luminance-qp-biasAdjusts frame QP based on average lumaInteger 0-100
sharpnessBias towards decreased/increased sharpnessInteger -7 to 7

GOP and Temporal Structure Parameters

ParameterDescriptionAllowed Values
lookaheadNumber of frames to look aheadInteger -1 to 120 (-1: auto)
hierarchical-levelsHierarchical levels beyond base layer2 – 3 temporal layers
3 – 4 temporal layers
4 – 5 temporal layers
5 – 6 temporal layers
pred-structPrediction structure1 – low delay frames
2 – random access
rtcFast settings for RTC in low-delay mode0 – off
1 – on

AV1 Coding Tools Parameters

ParameterDescriptionAllowed Values
enable-dlfDeblocking loop filter control0 – off
1 – on
enable-cdefEnable Constrained Directional Enhancement Filter0 – off
1 – on
enable-restorationEnable loop restoration filter0 – off
1 – on
enable-tpl-laTemporal Dependency model control (CRF/CQP only)0 – off
1 – on
enable-mfmvMotion Field Motion Vector control-1 – auto
0 – off
1 – on
enable-dgDynamic GoP control0 – off
1 – on
fast-decodeFast Decoder levels0, 1, or 2
enable-overlaysEnable insertion of overlayer pictures0 – off
1 – on

Tuning and Content Parameters

ParameterDescriptionAllowed Values
tuneTuning metric0 – VQ
1 – PSNR
2 – SSIM
scmScreen content detection level0 – off
1 – on
2 – content adaptive
film-grain-denoiseApply denoising when film grain is ON0 – no denoising
1 – level set by film-grain parameter

Super-Resolution Parameters

ParameterDescriptionAllowed Values
superres-modeSuper-resolution mode0 – off
1, 2, 3 – on
4 – auto-select
superres-denomSuper-resolution denominator (mode 1 only)Integer 8-16 (8: no scaling, 16: half-scaling)
superres-kf-denomSuper-resolution denominator for key frames (mode 1 only)Integer 8-16
superres-qthresSuper-resolution q-threshold (mode 3 only)Integer 0-63
superres-kf-qthresSuper-resolution q-threshold for key frames (mode 3 only)Integer 0-63

S-Frame Parameters

ParameterDescriptionAllowed Values
sframe-distS-Frame interval in framesInteger >= 0 (0: off)
sframe-modeS-Frame insertion mode1 – only if altref frame
2 – next altref frame

Color Metadata Parameters

ParameterDescriptionAllowed Values
color-primariesColor primariesInteger 0-22
transfer-characteristicsTransfer characteristicsInteger 0-22
matrix-coefficientsMatrix coefficientsInteger 0-14
color-rangeColor range0 – Studio
1 – Full
chroma-sample-positionChroma sample positionunknown, vertical, left, colocated, topleft

Variance Boost Parameters

ParameterDescriptionAllowed Values
enable-variance-boostEnable variance boost0 – off
1 – on
variance-boost-strengthVariance boost strengthInteger 1-4
variance-octileOctile for variance boostInteger 1-8

Updated parameters

  • preset - Range extended from 0-8 to -1 to 13
  • rc - Changed from text values (cqp, vbr, cvbr) to numeric (0, 1, 2). Note: cvbr is no longer supported
  • qp - Range changed from -1 to 64 to 1-63
  • min-qp - Renamed from qmin, range changed to 1-63
  • max-qp - Renamed from qmax, range changed to 1-63
  • irefresh-type - Now supports Open GOP (1) and Closed GOP (2)
  • enable-tf - Range extended from 0-1 to 0-2
  • tbr - Now accepts b/k/m suffixes
  • scd - Renamed from sc_detection

Removed deprecated parameters

  • tier - No longer available in current SVT-AV1
  • la_depth - Replaced by lookahead
  • sc_detection - Replaced by scd
  • qmin - Replaced by min-qp
  • qmax - Replaced by max-qp