H264Profile

constant rate factor of the software encoder (default is 23)

Encode colors at full resolution (4:4:4, the yuv444p pixel format) instead of at half resolution (4:2:0). This keeps the colors of thin lines and edges, but the video does not play in web browsers. Of the hardware encoders only NVENC encodes 4:4:4, with full chroma the software encoder is used instead of the others.

The transfer function of HDR video, null for SDR video. HDR profiles take frames with linear colors in which 1.0 is SDR white, the reference white of HDR video (203 nits), like the frames of HDR windows.

the preset of the software encoder

constant quality of the hardware encoders, from 1 to 100 where higher is better, or null for their default bitrate. The default of 60 is comparable to the default constant rate factor of the software encoder.

Rotates the frames, a 90 degree rotation swaps the width and height of the video. The pixels are rotated, the video is not tagged with a rotation that players apply.

the DRM render node that the VAAPI encoder encodes with, set by hardwareAcceleration

Encode with a hardware encoder, which uses a fraction of the CPU time of the software encoder: VideoToolbox on macOS, on Linux NVENC on NVIDIA GPUs or VAAPI on Intel and AMD GPUs, and on Windows NVENC on NVIDIA GPUs, Quick Sync on Intel GPUs, AMF on AMD GPUs or else the hardware encoder of Media Foundation. On Linux and Windows the encoders are tried with the ffmpeg executable that VideoWriter runs, the software encoder is kept when none of them works, see findHardwareEncoder.

Arguments for the frames that are fed to the encoder, these are passed before the input