ffmpeg time position rounding

**missing.bracket** · May 16th, 2010

I've written a bash script that extracts the audio out of a movie file and saves it out in separate .wav files using ffmpeg. Here is the key ffmpeg command:

Code:

ffmpeg -i $movie_file -vn -ss $start_time -t $duration ${file_name}_${counter}.wav

$start_time and $duration are floating point numbers that contain time information in the form of seconds and milliseconds (ss.xxx). It is important that I am able to control the time down to the millisecond.

My script works exactly as hoped on .avi files.

My script needs to work on an existing archive of .mov files. My problem is, when I try to use it on a .mov, the audio files created always have start times and durations that have been rounded up to the nearest half-second. This breaks up the audio in the wrong spots, and creates files that last too long and have too much extra audio.

What can I do to make my ffmpeg command create .wav files from .mov files that properly recognize a specific number of milliseconds? Or, asked another way, how can I eliminate the rounding behavior?

Thanks!

**missing.bracket** · May 17th, 2010

Any ideas? Would it be helpful if I supplied more information? Is there a better place for me to direct this question?

**FakeOutdoorsman** · May 17th, 2010

Have you tried placing -ss (and possibly -t) before your input? I'm not sure if it will help, but it is worth a try. Stop by the #ffmpeg IRC channel and ask there too.

**missing.bracket** · May 18th, 2010

I hadn't considered changing the order of the input parameters. I've given it a shot and (alas) it doesn't change the rounding in the creation of the output file. Thanks for the input, though!