A significant number of options are exposed for defining the cadence of frames, within a decodable segment of time referred to as a GOP (Group of Pictures.) By default, output will have variable length GOPs optimized around detection of scene changes, with each GOP at least 25 frames in length between IDR frames.
It is possible to force fixed GOPs by setting keyint and keyint_min to the same number. This is frequently helpful when using adaptive bitrate packages so segments align. To disable non-IDR scenecut keyframes, you can also set sc_threshold to zero.
Specify the minimum distance between I-frames.
As set of constraints that specify decoder performance for a profile.
high profile, main profile, iphone_stream, roku: 30(3.0)
Specify the sensitivity of x264's scenecut detection.
Specify the number of b-frames.
Adaptively decides through a low-resolution lookahead the best number of B-frames.
0, 1, 2
CABAC is the default entropy encoder used by x264.
Specify how many references can be used, through a maximum of 16.
Enable or disable the loop filter.
One of H.264's main features is the in-loop deblocker, which avoids the problem of blocking artifacts disrupting motion estimation.
0 (Must have '-flags +loop')
Specify the direct MV prediction mode.
0 — none,
main, high, baseline, smooth_streaming — 1,
Specify the amount of Adaptive Quantization(AQ) that is applied to the frames.
Positive float number
Enable constant framerate.
For level parameter
Drop the decimal, for example 3.0 is 30, 1.3 is 13.