Advanced NVENC Options (31.0)

2024-08-21

Starting with OBS 31.0 the NVENC implemenation provides additional options for adjusting the NVIDIA encoder settings.

New Properties

Rate Control: Variable Bitrate with Target Quality

New mode behaving similarly to CQP, but with the option to set a maximum bitrate to provide a high quality while limiting file size or stream bitrate.

Tuning: Ultra High Quality

New tuning option optimised for live-action with artifacts such as camera sensor noise. Not recommended for gaming content. Significantly reduces throughput.

Adaptive Quantization

Same as "Psycho-Visual Tuning" but now with the proper nomenclature rather than a confusing marketing term.

B-Frame as Reference (HEVC/AV1 only)

Enables using B-Frames as reference frames, can slightly improve quality with no performance impact. Recommended when using multiple B-Frames.

Split Encode (HEVC/AV1 only)

Requires NVIDIA Ada Generation GPU with two or more NVENC engines (4070 Ti or higher).

Splits frame across multiple NVENC engines to achieve higher throughput with near-linear scaling. Automatically used when using fast presets (p1-p2 in high quality, p1-p4 in low latency modes) with resolutions above 2160p (UHD/4K). Manually forcing it to be used may allow using slower presets such as p7 at higher resolutions while maintaining real-time encoding. Note that at low bitrates there may be a visible seam between the two frame halves.

See NVIDIA's developer blog for more details.

Custom Options

Allow specifying additional low-level encoder properties manually in the form of option=value pairs separated by spaces.

General Options

Option Description

Option	Description
`keyint`	Note: Not a standard NVENC option. Keyframe interval in frames, supports special value of `1` for intra-only mode.
`frameIntervalP`	Specifies the GOP pattern as follows: I IPP IBP IBBP If goplength is set to NVENC_INFINITE_GOPLENGTH frameIntervalP should be set to 1.
`gopLength`	Note: Except for the special case of infinite GOP, `keyint` should be used instead. Specifies the number of pictures in one GOP. Low latency application client can set goplength to `NVENC_INFINITE_GOPLENGTH` (4294967295) so that keyframes are not inserted automatically.

keyint

Note: Not a standard NVENC option.

Keyframe interval in frames, supports special value of 1 for intra-only mode.

frameIntervalP

Specifies the GOP pattern as follows:

I
IPP
IBP
IBBP

If goplength is set to NVENC_INFINITE_GOPLENGTH frameIntervalP should be set to 1.

gopLength

Note: Except for the special case of infinite GOP, keyint should be used instead.

Specifies the number of pictures in one GOP. Low latency application client can set goplength to NVENC_INFINITE_GOPLENGTH (4294967295) so that keyframes are not inserted automatically.

Rate Control Options

Option	Description
`constQP=<N>`/`constQP=<I>:<P>:<B>`	Specifies the initial QP to be used for encoding, these values would be used for all frames if in Constant QP mode.
`minQP=<N>`/`minQP=<I>:<P>:<B>`	Specifies the minimum QP used for rate control. Also requires `enableMinQP=1` to be set.
`maxQP=<N>`/`maxQP=<I>:<P>:<B>`	Specifies the maximum QP used for rate control. Also requires `enableMaxQP=1` to be set.
`initialRCQP=<N>`/`initialRCQP=<I>:<P>:<B>`	Specifies the initial QP hint used for rate control. The parameter is just used as hint to influence the QP difference between I,P and B frames. Also requires `enableInitialRCQP=1` to be set.
`averageBitRate`	Specifies the average bitrate(in bits/sec) used for encoding.
`maxBitRate`	Specifies the maximum bitrate for the encoded output. This is used for VBR and ignored for CBR mode.
`vbvBufferSize`	Specifies the VBV(HRD) buffer size. in bits. Set 0 to use the default VBV buffer size.
`vbvInitialDelay`	Specifies the VBV(HRD) initial delay in bits. Set 0 to use the default VBV initial delay.
`targetQuality`	Target CQ (Constant Quality) level for VBR mode (range 0-51 with 0-automatic).
`enableLookahead`	Set this to 1 to enable lookahead.
`disableIadapt`	Set this to 1 to disable adaptive I-frame insertion at scene cuts (only has an effect when lookahead is enabled)
`disableBadapt`	Set this to 1 to disable adaptive B-frame decision (only has an effect when lookahead is enabled)
`enableAQ`	Set this to 1 to enable adaptive quantization (Spatial).
`enableTemporalAQ`	Set this to 1 to enable temporal AQ.
`aqStrength`	When AQ (Spatial) is enabled, this field is used to specify AQ strength. AQ strength scale is from 1 (low) - 15 (aggressive). If not set, strength is auto selected by driver.
`lookaheadLevel`	Specifies the lookahead level. Higher level may improve quality at the expense of performance.
`lookaheadDepth`	Maximum depth of lookahead with range 0-(31 - number of B frames).

H.264 Options

Option	Description
`level`	Specifies the encoding level. Client is recommended to set this to `NV_ENC_LEVEL_AUTOSELECT` (0) in order to enable the NVENC interface to select the correct level. Can be specified as a decimal number, e.g. `4.2`
`useBFramesAsRef`	Specifies the B-Frame as reference mode.
`enableFillerDataInsertion`	Set to 1 to enable insertion of filler data in the bitstream. This flag will take effect only when CBR rate control mode is in use

HEVC Options

Options	Description
`level`	Specifies the level of the encoded bitstream. Can be specified as a decimal number, e.g. `4.2`
`tier`	Specifies the level tier of the encoded bitstream.
`useBFramesAsRef`	Specifies the B-Frame as reference mode.
`tfLevel`	Specifies the strength of the temporal filtering. Temporal filter feature is supported only if frameIntervalP >= 5. Temporal filter is recommended for natural contents.
`enableFillerDataInsertion`	Set to 1 to enable insertion of filler data in the bitstream. This flag will take effect only when CBR rate control mode is in use

AV1 Options

Option	Description
`level`	Specifies the level of the encoded bitstream.
`tier`	Specifies the level tier of the encoded bitstream.
`numTileColumns`	This parameter specifies the way in which the picture is divided into tile columns. The picture will be uniformly divided into `numTileColumns` tile columns. If `numTileColumns` is not a power of 2, it will be rounded down to the next power of 2 value. If `numTileColumns=0`, the picture will be coded with the smallest number of vertical tiles as allowed by standard. Note: A larger amount of tiles can help with decoding speed. By default, OBS sets this to 2 for resolutions of 2160p or above.
`numTileRows`	This parameter specifies the way in which the picture is divided into tiles rows. The picture will be uniformly divided into `numTileRows` tile rows. If `numTileRows` is not a power of 2, it will be rounded down to the next power of 2 value. If `numTileRows=0`, the picture will be coded with the smallest number of horizontal tiles as allowed by standard. Note: A larger amount of tiles can help with decoding speed.
`useBFramesAsRef`	Specifies the B-Frame as reference mode.
`enableBitstreamPadding`	Set 1 to enable bitstream padding.

See NVIDIA's documentation for more detailed explanations of various options.