Don't give subprocess our stdin, give it os.devnull instead.

[mwoenker]

When calling subprocess.Popen to call ffmpeg, the process inherits our standard input. Apparently ffmpeg modifies the terminal parameters if it is given a TTY on standard in. Usually this isn't a problem, because ffmpeg sets them back to what they were when it is done. However if you're calling AudioSegment.from_file() or AudioSegment.export() from multiple threads at once, the multiple ffmpeg process race each other in setting/getting the shared terminal parameters.

On my machine at least, this pretty consistently leaves my terminal hosed when my program exits -- turning off echoing, and other weirdness, which is only fixed by blindly typing reset into the terminal.

The easy solution seems to be to just give ffmpeg/avconv a file descriptor to os.devnull on stdin, which fixes the problem for me. Tested with ffmpeg, not with avconv, but I would be surprised if it broke anything.