FFmpeg filter graph

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FFmpeg filter graph by Ciro Santilli 34 Updated 2024-12-15 +Created 1970-01-01
Filter graphs are a thing of great beauty. What an amazingly obscure domain-specific language, but which can produce striking results with very little!!!
ffplay -autoexit -nodisp -f lavfi -i '
sine=frequency=500[a];
sine=frequency=1000[b];
[a][b]amerge, atrim=end=2
'
which creates a graph:
                              +--------+
[sine=frequency=500]--->[a]-->|        |
                              | amerge |-->[atrim]-->[output]
[sine=frequency=1000]-->[b]-->|        |
                              +--------+
and plays 500 Hz on the left channel and 1000 Hz on the right channel for 2 seconds.
So we see the following syntax patterns:
  • sine, amerge and atrim are filters
  • sine=frequency=500: the first = says "araguments follow"
    • frequency=500 sets the frequency argument of the sine filter
    • for multiple arguments the syntax is to separate arguments with colons e.g. sine=frequency=500:duration=2
  • ;: separates statements
  • [a], [b]: sets the name of an edge
  • ,: creates unnamed edge between filters that have one input and one output
A list of all filters can be obtained ith:
ffmpeg -filters
and parameters for a single filter can be obtained with:
ffmpeg --help filter=sine
Related question: stackoverflow.com/questions/69251087/in-ffmpeg-command-line-how-to-show-all-filter-settings-and-their-parameters-bef
TODO dump graph to ASCII art? trac.ffmpeg.org/wiki/FilteringGuide#Visualizingfilters mentions a -dumpgraph option, but haven't managed to use it yet.
Bibliography:
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