Get the process bar of ffmpeg

ffmpeg_backend.py

#!/usr/bin/env python3

from io import BytesIO
def ffmpeg_it(clip, input, output, overwriteopt='-y'):
    cmd = [ffmpeg, '-ss', clip['start'], '-i', input, '-c', 'copy',
           '-t', clip['end'], overwriteopt, output ]
    ffmpegp = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    buf = BytesIO()
    while True:
        # put the single char to IO buffer in case it's a multi-byte
        # character, utf8 for example
        out = ffmpegp.stdout.read(1)
        buf.write(out)
        # decode and display output only when \r or \n met
        # it doens't matter for '\n\r' sequence because there is no
        # more char in between, they will be printed in adjoint loop,
        # as without buffer
        if out in (b'\r', b'\n'):
            sys.stdout.write(buf.getvalue().decode().strip('\x00'))
            buf.truncate(0)

        if ffmpegp.returncode is None:
            if ffmpegp.poll() is not None: break
        else:
            break;