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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| Name | Target Usage | Source | ffmpeg flags | Description | Size |
|---|---|---|---|---|---|
| x264 -pix_fmt yuv420p | 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. Final review, e.g. lighting | |||
| x264 -pix_fmt yuv444p10le | Final review, e.g. lighting | 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 | ||
| x264rgb | x264rgbFinal review, e.g. lighting | This is a variant of the above, its essentially using x264, but not converting to YCrCb. | |||
| Prores 4444 | For delivery to editorial | -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 | |||
DnxHD | For delivery to editorial | ||||
| Prores 422 HQ | For delivery to editorial | 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 | |||||
x264
Key flags (see https://trac.ffmpeg.org/wiki/Encode/H.264 )
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- An excellent starting point for this is: https://trac.ffmpeg.org/wiki/colorspace
- https://github.com/RxLaboratory/DuME/blob/master/src/FFmpeg_COLORS.md
- https://medium.com/invideo-io/talking-about-colorspaces-and-ffmpeg-f6d0b037cc2f
- https://docs.nvidia.com/video-technologies/video-codec-sdk/ffmpeg-with-nvidia-gpu/
- https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.1886-0-201103-I!!PDF-E.pdf - the BT1886 spec, esentially gamma 2.4 rec709 primaries.
- https://github.com/bbc/qtff-parameter-editor - A BBC open source app, for setting quicktime NCLC attributes.
- https://vimeo.com/349868875 - Video from baselight, reviewing setting the right NCLC tags for apple colorsync.
Notes
The big issue here is that by default if you start converting images to another format, and ffmpeg cannot determine the colorspace it will default to bt601. So many of the flags below are to:
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C: Do as clean a conversion from RGB to YUV as possible.
RGB/
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YCrCb Colorspace Conversion
As a rule of thumb, we would like ffmpeg to do as little as possible in terms of color space conversion. i.e. what comes in goes out. The problem is that most of the codecs are doing some sort of RGB to YUV conversion (technically YCrCb). The notable exception is x264rgb (see above). For more information, see: https://trac.ffmpeg.org/wiki/colorspace and
While it is possible to do the encoding outside of ffmpeg (see later).
For examples comparing these see: https://richardssam.github.io/ffmpeg-tests/tests/chip-chart-yuvconvert/compare.html
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This is the most basic colorspace filtering. bt470bg is essentially part of the bt601 spec. See: https://www.ffmpeg.org/ffmpeg-filters.html#colormatrix
colorspace filter
ffmpeg -y -i ../sourceimages/chip-chart-1080-noicc.png -sws_flags spline+accurate_rnd+full_chroma_int -vf "colorspace=bt709:iall=bt601-6-625:fast=1" -c:v libx264 -preset placebo -qp 0 -x264-params "keyint=15:no-deblock=1" -pix_fmt yuv444p10le -qscale:v 1 -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 ./chip-chart-yuvconvert/spline444colorspace.mp4
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The docs are pretty sparse for this, some of the better info is FFmpeg/pixfmt.h at master · FFmpeg/FFmpeg · GitHub
links:
Color Range
Uses the flag -color_range e.g. -color_range 1 or -color_range tv
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- https://vimeo.com/349868875
- https://developer.apple.com/documentation/avfoundation/media_assets_and_metadata/sample-level_reading_and_writing/tagging_media_with_video_color_information
- https://www.iso.org/standard/73412.html - Note this has a link to the download of the earlier version of the doc, the latest and paywalled version is here: https://www.iso.org/standard/57794.html
- https://github.com/bbc/qtff-parameter-editor - A BBC open source app, for setting quicktime NCLC attributes.
- https://vimeo.com/349868875 - Video from baselight, reviewing setting the right NCLC tags for apple colorsync.
Web Browser Deliverables
How should we be encoding content for a web browser.
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