Advanced features for managing the frames in your output.
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.
| Parameter | Description | Allowed Values | Default Value |
|---|---|---|---|
| keyint_min | Specify the minimum distance between I-frames. | Positive integer number | none (automatically determined by codec) |
| level | As set of constraints that specify decoder performance for a profile. | Positive integer number | high profile, main profile, iphone_stream, roku: 30(3.0) baseline profile: 13(1.3) |
| open-gop | Use recovery points to close GOPs, only available with b-frames | 1, 0 | none |
| sc_threshold | Specify the sensitivity of x264's scenecut detection. | Positive integer number | 40 |
| bf | Specify the number of b-frames. | Positive integer number | 16 |
| b_strategy | Adaptively decides through a low-resolution lookahead the best number of B-frames. | 0, 1, 2 | 1 |
| coder | CABAC is the default entropy encoder used by x264. | 0, 1 | 1(CABAC enabled) |
| refs | Specify how many references can be used, through a maximum of 16. | Positive integer number | baseline profile: 3 main profile: 6 high profile: 4 |
| flags | Enable or disable the loop filter. | -loop/+loop, -psnr/+psnr | +loop (Enabled) |
| deblockalpha, deblockbeta | One of H.264's main features is the in-loop deblocker, which avoids the problem of blocking artifacts disrupting motion estimation. | Positive integer number | 0 (Must have '-flags +loop') |
| directpred | Specify the direct MV prediction mode. | 0 — none, 1 — spatial 2 — temporal 3 — auto | main, high, baseline, smooth_streaming — 1, roku — 3 |
| aq-strength | Specify the amount of Adaptive Quantization(AQ) that is applied to the frames. | Positive float number 0.5 – low AQ 1.5 – strong AQ | 1.0 |
| force-cfr | Enable constant framerate. | 1, 0 | 0 |
For level parameter
Drop the decimal, for example 3.0 is 30, 1.3 is 13.