FFmpeg is frequently used by different studios for encoding their media, however the documentation for ffmpeg is often poor, or cryptic so its often harder than it should be to come up with a good starting point. We are aiming to come up with recommendations for different scenarios as well as document what the different flags are doing with the aim to make this easier to get to a good baseline.
...
| Name | Source | ffmpeg flags | Description | Size |
|---|---|---|---|---|
| colorspace_yuv444p10le | https://trac.ffmpeg.org/wiki/colorspace | -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" -pix_fmt yuv444p10le -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625:fast=1" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 | ||
| Prores 4444 | -c:v prores_ks -profile:v 4444 -qscale:v 1 -pix_fmt yuv444p10le -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625:fast=1" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 | |||
| -profile:v 4444 is equivalent to -profile:v 4 | ||||
| shotgun_diy_encode | https://support.shotgunsoftware.com/hc/en-us/articles/219030418-Do-it-yourself-DIY-transcoding', | -vcodec libx264 -pix_fmt yuv420p -g 30 -vprofile high -bf 0 -crf 2 | ||
| Prores 422 HQ | Some FFMpeg commands I need to remember for converting footage for video editing. http://bit.ly/vidsnippets · GitHub |
| ||
Note the -profile:v 3 is equivalent to -profile:v hq | ||||
VMAF
I did explore using VMAF - Video Multi-Method Assessment Fusion as a way to quantify the compression, the notes for setting this up are below, however I think we are going with a fairly high compression factor , so I think this is probably not really going to help us much.
...
Uses the flag -color_range e.g. -color_range 1 or -color_range tv
| Numeric value | String Values | Numeric range | Notes |
|---|---|---|---|
| 0 | Unspecified | ||
| 1 | tv mpeg | 16-135 | This is the default. |
| 2 | pc jpeg | 0-255 |
Color Space
This defines the YUV colorspace type, as defined by ISO/IEC 23091-2_2019 subclause 8.3
...
This is a subset of the full list of values, for more details, see FFmpeg/pixfmt.h at master · FFmpeg/FFmpeg · GitHub
| Numeric Value | String values | Description |
|---|---|---|
| 0 | rgb | |
| 1 | bt709 | Typically set it to this. |
| 2 | unspecified | |
| 9 | bt2020nc bt2020_ncl | ITU-R BT2020 non-constant luminance system |
| 10 | bt2020c bt2020_cl | ITU-R BT2020 constant luminance system |
Color Primaries
Chromaticity coordinates of the source primaries. These values match the ones defined by ISO/IEC 23091-2_2019 subclause 8.1 and ITU-T H.273.
...
This is a subset of the full list of values, for more details, see FFmpeg/pixfmt.h at master · FFmpeg/FFmpeg · GitHub
| Numeric Value | String Values | Description |
|---|---|---|
| 1 | bt709 | |
| 9 | bt2020 |
Color Transfer Characteristic aka color_trc
...
This is defines the OETF, which typically is the gamma.
| Numeric Value | String Values | Description |
|---|---|---|
| 1 | bt709 | Note this is the camera gamma i.e. ~1.95 this is NOT bt1886 |
| 2 | Image characteristics are unknown or are determined by the application. | |
| 4 | gamma22 | |
| 5 | gamma28 | |
| 8 | linear | Linear |
| 9 | log log100 | |
| 14 | bt2020_10 bt2020_10bit | Note this is the camera gamma i.e. ~1.95 |
| 15 | bt2020_12 bt2020_12bit | Note this is the camera gamma i.e. ~1.95 |
| Numeric Value | String Values | Description |
|---|---|---|
| 1 | bt709 | Note this is the camera gamma i.e. ~1.95 this is NOT bt1886 |
| 2 | Image characteristics are unknown or are determined by the application. | |
| 4 | gamma22 | |
| 5 | gamma28 | |
| 8 | linear | Linear |
NOTE: -color_trc 1 - is not bt1886, but is actually the camera gamma, so has a gamma of ~1.95 rather than the 2.4 that is defined by bt1886. In order to get a gamma 2.4, you will need to use a quicktime hack (see below), but this only works on OSX. However, we suspect that chrome ignores the setting (see the following tests).
...