I used to calculate the duration of MP3 files server-side using ffmpeg - which seemed to work fine. Today i discovered that some of the calculations were wrong. Somehow, for some reason, ffmpeg will miscalculate the duration and it seems to happen with variable bit rate mp3 files only.

When testing this locally, i noticed that ffmpeg printed two extra lines in green.

Command used:

ffmpeg -i song_9747c077aef8.mp3

ffmpeg says:

[mp3 @ 0x102052600] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate

After a nice, warm google session, i found some posts on this, but no solution was found.

I then tried to increase the maximum duration:

ffmpeg -analyzeduration 999999999 -i song_9747c077aef8.mp3

After this, ffmpeg returned only the second line:

[mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate

But in either case, the calculated duration was just plain wrong. Comparing it to VLC i noticed that here the duration is correct.

After more research i stumbled over mp3info - which i installed and used.

mp3info -p "%S" song_9747c077aef8.mp3

mp3info then returned the CORRECT duration, but only as an integer, which i cannot use as i need a more accurate number here. The reason for this was explained in a comment below, by user blahdiblah - mp3info is simply pulling ID3 info from the file and not actually performing any calculations.

I also tried using mplayer to retrieve the duration, but just as ffmpeg, mplayer is returning the wrong value.

Now i ran out of options.

If somebody knows how to get around this, any hints, tips, guides or corrections are welcome!

Thank You!