How to use argument with dash in name in ffmpeg-python?

Question

Following is a simple ffmpeg command line for encoding an input video into a AV1 output with CRF 30:

ffmpeg -i input.mkv -c:v libsvtav1 -crf 30 output.mkv

Converting that command line into the syntax of ffmpeg-python is pretty straight-forward:

(
    ffmpeg
    .input('input.mkv')
    .output('output.mkv', vcodec='libsvtav1', crf=30)
    .run()
)

However, what happens if we want to specify the fast-decode option? In ffmpeg that would mean extending our command line to include -svtav1-params fast-decode=1, i.e.:

ffmpeg -i input.mkv -c:v libsvtav1 -crf 30 -svtav1-params fast-decode=1 output.mkv

How do we specify the same thing in ffmpeg-python? Adding svtav1-params='fast-decode=1' into the output arguments results in invalid Python code since variables are not allowed to have dash in the name:

(
    ffmpeg
    .input('input.mkv')
    .output('output.mkv', vcodec='libsvtav1', crf=30, svtav1-params='fast-decode=1')
    .run()
)
# Error: Expected parameter name

Replacing the dash with an underscore in the name makes ffmpeg-python read it literally which doesn't translate into a valid ffmpeg command line.

How is it possible to specify fast-decode and other svtav1-params specific arguments in ffmpeg-python?

Abrar Ahmed · Accepted Answer · 2023-05-08 13:20:19Z

3

According to the documentation, you can use the ** syntax to pass additional arguments for Special option names like this

(
    ffmpeg
    .input('input.mkv')
    .output('output.mkv', vcodec='libsvtav1', crf=30, **{'svtav1-params': 'fast-decode=1'})
    .run()
)

answered May 8, 2023 at 13:20

Abrar Ahmed

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