OBS uses nvenc when encoding live streams. In the guide "NVIDIA NVENC OBS Guide", an advanced option is listed as:
Keyframe Interval: Set to 2. Streaming platforms may limit what you can select here, and most require a setting of 2.
I want to do the same with ffmpeg, and we know the option exists in the nvenc API. However, listing the encoder's options with ffmpeg -h encoder=h264_nvenc (full output pasted below), the usual -keyint or -g options are not found. The most relevant ones are -forced-idr and -strict_gop.
How to set keyframe interval, either as number of frames or time duration in seconds, when using nvenc?
(While we are at it, the "Psycho Visual Tuning", "Max B-Frames" options in the guide are also missing. The latter should in theory be accessible by -bf:v 4. What about the former?)
ffmpeg version 4.3.1-2021-01-01-full_build- Copyright (c) 2000-2021 the FFmpeg developers built with gcc 10.2.0 (Rev5, Built by MSYS2 project) configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-libsnappy --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libzvbi --enable-librav1e --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint libavutil 56. 51.100 / 56. 51.100 libavcodec 58. 91.100 / 58. 91.100 libavformat 58. 45.100 / 58. 45.100 libavdevice 58. 10.100 / 58. 10.100 libavfilter 7. 85.100 / 7. 85.100 libswscale 5. 7.100 / 5. 7.100 libswresample 3. 7.100 / 3. 7.100 libpostproc 55. 7.100 / 55. 7.100
Encoder h264_nvenc [NVIDIA NVENC H.264 encoder]: General capabilities: delay hardware Threading capabilities: none Supported hardware devices: cuda cuda d3d11va d3d11va Supported pixel formats: yuv420p nv12 p010le yuv444p p016le yuv444p16le bgr0 rgb0 cuda d3d11
h264_nvenc AVOptions: -preset <int> E..V...... Set the encoding preset (from 0 to 11) (default medium) default 0 E..V...... slow 1 E..V...... hq 2 passes medium 2 E..V...... hq 1 pass fast 3 E..V...... hp 1 pass hp 4 E..V...... hq 5 E..V...... bd 6 E..V...... ll 7 E..V...... low latency llhq 8 E..V...... low latency hq llhp 9 E..V...... low latency hp lossless 10 E..V...... losslesshp 11 E..V...... -profile <int> E..V...... Set the encoding profile (from 0 to 3) (default main) baseline 0 E..V...... main 1 E..V...... high 2 E..V...... high444p 3 E..V...... -level <int> E..V...... Set the encoding level restriction (from 0 to 51) (default auto) auto 0 E..V...... 1 10 E..V...... 1.0 10 E..V...... 1b 9 E..V...... 1.0b 9 E..V...... 1.1 11 E..V...... 1.2 12 E..V...... 1.3 13 E..V...... 2 20 E..V...... 2.0 20 E..V...... 2.1 21 E..V...... 2.2 22 E..V...... 3 30 E..V...... 3.0 30 E..V...... 3.1 31 E..V...... 3.2 32 E..V...... 4 40 E..V...... 4.0 40 E..V...... 4.1 41 E..V...... 4.2 42 E..V...... 5 50 E..V...... 5.0 50 E..V...... 5.1 51 E..V...... -rc <int> E..V...... Override the preset rate-control (from -1 to INT_MAX) (default -1) constqp 0 E..V...... Constant QP mode vbr 1 E..V...... Variable bitrate mode cbr 2 E..V...... Constant bitrate mode vbr_minqp 8388612 E..V...... Variable bitrate mode with MinQP (deprecated) ll_2pass_quality 8388616 E..V...... Multi-pass optimized for image quality (deprecated) ll_2pass_size 8388624 E..V...... Multi-pass optimized for constant frame size (deprecated) vbr_2pass 8388640 E..V...... Multi-pass variable bitrate mode (deprecated) cbr_ld_hq 8 E..V...... Constant bitrate low delay high quality mode cbr_hq 16 E..V...... Constant bitrate high quality mode vbr_hq 32 E..V...... Variable bitrate high quality mode -rc-lookahead <int> E..V...... Number of frames to look ahead for rate-control (from 0 to INT_MAX) (default 0) -surfaces <int> E..V...... Number of concurrent surfaces (from 0 to 64) (default 0) -cbr <boolean> E..V...... Use cbr encoding mode (default false) -2pass <boolean> E..V...... Use 2pass encoding mode (default auto) -gpu <int> E..V...... Selects which NVENC capable GPU to use. First GPU is 0, second is 1, and so on. (from -2 to INT_MAX) (default any) any -1 E..V...... Pick the first device available list -2 E..V...... List the available devices -delay <int> E..V...... Delay frame output by the given amount of frames (from 0 to INT_MAX) (default INT_MAX) -no-scenecut <boolean> E..V...... When lookahead is enabled, set this to 1 to disable adaptive I-frame insertion at scene cuts (default false) -forced-idr <boolean> E..V...... If forcing keyframes, force them as IDR frames. (default false) -b_adapt <boolean> E..V...... When lookahead is enabled, set this to 0 to disable adaptive B-frame decision (default true) -spatial-aq <boolean> E..V...... set to 1 to enable Spatial AQ (default false) -spatial_aq <boolean> E..V...... set to 1 to enable Spatial AQ (default false) -temporal-aq <boolean> E..V...... set to 1 to enable Temporal AQ (default false) -temporal_aq <boolean> E..V...... set to 1 to enable Temporal AQ (default false) -zerolatency <boolean> E..V...... Set 1 to indicate zero latency operation (no reordering delay) (default false) -nonref_p <boolean> E..V...... Set this to 1 to enable automatic insertion of non-reference P-frames (default false) -strict_gop <boolean> E..V...... Set 1 to minimize GOP-to-GOP rate fluctuations (default false) -aq-strength <int> E..V...... When Spatial AQ is enabled, this field is used to specify AQ strength. AQ strength scale is from 1 (low) - 15 (aggressive) (from 1 to 15) (default 8) -cq <float> E..V...... Set target quality level (0 to 51, 0 means automatic) for constant quality mode in VBR rate control (from 0 to 51) (default 0) -aud <boolean> E..V...... Use access unit delimiters (default false) -bluray-compat <boolean> E..V...... Bluray compatibility workarounds (default false) -init_qpP <int> E..V...... Initial QP value for P frame (from -1 to 51) (default -1) -init_qpB <int> E..V...... Initial QP value for B frame (from -1 to 51) (default -1) -init_qpI <int> E..V...... Initial QP value for I frame (from -1 to 51) (default -1) -qp <int> E..V...... Constant quantization parameter rate control method (from -1 to 51) (default -1) -weighted_pred <int> E..V...... Set 1 to enable weighted prediction (from 0 to 1) (default 0) -coder <int> E..V...... Coder type (from -1 to 2) (default default) default -1 E..V...... auto 0 E..V...... cabac 1 E..V...... cavlc 2 E..V...... ac 1 E..V...... vlc 2 E..V...... -b_ref_mode <int> E..V...... Use B frames as references (from 0 to 2) (default disabled) disabled 0 E..V...... B frames will not be used for reference each 1 E..V...... Each B frame will be used for reference middle 2 E..V...... Only (number of B frames)/2 will be used for reference -a53cc <boolean> E..V...... Use A53 Closed Captions (if available) (default true) -dpb_size <int> E..V...... Specifies the DPB size used for encoding (0 means automatic) (from 0 to INT_MAX) (default 0)1 Answer
-g is a generic option for codecs and should be used here. -g is nominated in frames.
-h encoder=X will only list private options of X.
