Ffmpeg-python: How can you pipe the output to ffplay?

[oveddan]

Is there a way to pipe the output live to ffplay so it can be viewed immediately?

[kkroening]

One way is to run the ffmpeg process with raw video output over a pipe, and then have ffplay decode the raw video. Something like this:

import ffmpeg
import subprocess

in_filename = 'in.mp4'
width, height = 1920, 1080  # (or use ffprobe or whatever)

process1 = (
    ffmpeg
    .input(in_filename)
    # (filters/etc. go here)
    .output('pipe:', format='rawvideo', pix_fmt='rgb24')
    .run_async(pipe_stdout=True)
)
process2 = subprocess.Popen(
    [
        'ffplay',
        '-f', 'rawvideo',
        '-pix_fmt', 'rgb24',
        '-s', '{}x{}'.format(width, height),
        '-i', 'pipe:',
    ],
    stdin=process1.stdout,
)
process1.wait()
process2.wait()

FYI there's no direct support for ffplay in ffmpeg-python currently.

[NiccoloGranieri]

@kkroening thanks so much for this! I wanted to ask a question related to the code above:

If I implement any kind of filtering in the section you marked with: # (filters/etc. go here) I seem to be unable to live affect the args given to the filters. So if for example blur the image by calling:

.filter('gblur', sigma=blurIndex)

and I try to increment blur index in time only the first value seems to affect the video. Do you know if it's even possible to affect the filter parameters live?

[kkroening]

Do you know if it's even possible to affect the filter parameters live?

There is no way that I know of to change ffmpeg filter graphs dynamically.