flv_size / mp4_size comparison is a little too sensitive

[John Grieve]

When downloading short episodes that compress well the code:

common.py

if abs(flv_size - mp4_size) < 0.1 * flv_size:
            os.unlink(infile)
            return True
        else:
            logging.error("The size of %s is suspicious, did the remux fail?", outfile)
            return False

is just a little bit too sensitive. Chaning 0.1 to 0.2 fixes the issue.

the ABC's "Hey Duggee S01E08" is an example.

[delx]

This should be fixed, now it uses the duration as reported by ffprobe :)