Simple stream selection?

I’m trying to do some simple stream selection. Using ffmpeg directly, I’d use the map option. However, when trying to do this using ffmpeg-python, I can’t seem to get it correct. The map argument is getting put into a bracket, which doesn’t work.

>>> import ffmpeg
>>> infile = ffmpeg.input('test.mkv')
>>> stream = infile['1']
>>> outfile = ffmpeg.output(stream, 'test-out.mkv')
>>> ffmpeg.compile(outfile)
['ffmpeg', '-i', 'test.mkv', '-map', '[0:1]', 'test-out.mkv']

This fails with the error Output with label '0:1' does not exist in any defined filter graph, or was already used elsewhere.

What is the proper way to do stream selection when you don’t need complex video graphs?

[kkroening]

@whichken I think your example syntax in the first comment makes the most sense:

import ffmpeg
infile = ffmpeg.input('test.mkv')
outfile = ffmpeg.output(infile['1'], 'test-out.mkv')

And similarly for multiple streams:

infile = ffmpeg.input('test.mkv')
outfile = ffmpeg.output(infile['1'], infile['2'], 'test-out.mkv')

I consider it a bug that -map [0:1] is produced instead of -map 0:1. Will try to make a fix soon.

[kkroening]

Or perhaps eventually this shorthand would make things simpler:

infile = ffmpeg.input('test'.mk4')
outfile = ffmpeg.output(infile[[1, 2]], 'test-out.mkv')

or fluently:

(
    ffmpeg
    .input('test.mk4')
    [[1, 2]]
    .output('test-out.mkv')
    .run()
)

The [] operator would basically take either a single identifier (e.g. ['v']) or a list of identifiers (e.g. [[1, 2]]). This is similar to how a library like Pandas operates.