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.
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| Codec | Target Usage | Description | |||
|---|---|---|---|---|---|
| x264 | Proxy playback, for web review, and non-color critical workflows, e.g. animation, modeling, etc. | This should be a lightweight compression, capable of supporting HD with a reasonable bit-rate, hopefully supporting a wide range of web browsers. | |||
| x264 | Final review, e.g. lighting | This would still be using the vanilla x264 encoding, but may be using some of the more advanced settings, so may not function on all web browsers, the goal would be the best maintenance of color, possibly at 10-bit. | |||
x264rgb | Final review, e.g. lighting | This is a variant of the above, its essentially using x264, but not converting to YCrCb. | ProresDnxHD | For delivery to editorial.g. lighting | This is a variant of the above, its essentially using x264, but not converting to YCrCb. |
ProresDnxHD | For delivery to editorial |
x264
Key flags (see https://trac.ffmpeg.org/wiki/Encode/H.264 )
- -crf 23 - This is the constant rate factor, controlling the default quality (see: https://slhck.info/video/2017/02/24/crf-guide.html ) where -crf 0 is uncompressed. By default this is set to 23, which is probably good enough for our needs.
- -qp 23 - Quantization Parameter - it is recommended that you do not use this, in preference to -crf above (see: https://slhck.info/video/2017/03/01/rate-control.html )
- -preset slow - https://trac.ffmpeg.org/wiki/Encode/H.264#FAQ
- -tune film - Optionally use the tune option to change settings based on specific inputs - https://trac.ffmpeg.org/wiki/Encode/H.264#FAQ
TODO:
- Suggestions for max-bitrate?
- Suggestions for preset - ? slow
- Suggestions for tune
Color Preservation
Testing Methodology
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| 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.
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https://ottverse.com/vmaf-ffmpeg-ubuntu-compilation-installation-usage-guide/ - building VMAF on ubuntu.
ffmpeg flags
Codec
x264
x264rgb
Prores
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RGB/YCrVb Colorspace Conversion
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