This adds some shorthand operators for dealing with audio/video sub-streams.
Old:
input = ffmpeg.input('in.mp4')
audio = input['a'].filter("aecho", 0.8, 0.9, 1000, 0.3)
video = input['v'].hflip()
out = ffmpeg.output(audio, video, 'out.mp4')
New:
input = ffmpeg.input('in.mp4')
audio = input.audio.filter("aecho", 0.8, 0.9, 1000, 0.3)
video = input.video.hflip()
out = ffmpeg.output(audio, video, 'out.mp4')
The old method still works and is equivalent, but the new is probably more intuitive for most use cases.