Convert from Opus to Mp3 format results in unmatch length of track

[duytrung]

Hi all,

I used Freac converter which convert a mp3 track to opus then from the opus back to mp3. However, the lengths of the original and converted is now different. Could you give explanation?

Kind regards

Will

[rillian]

How much different?

Opus supports sample-accurate audio durations, but the older mp3 format does not. I'm not familiar with freac. It's possible it doesn't implement trimming correctly, or that it changed the sample rate in a way which made it impossible to match the duration between the two mp3 versions. Either of those could cause a slight change in the playback length.

If you mean the size of the compressed files, that's normal. Both opus an mp3 are lossy compression techniques, and depending on the exact compression settings and the details of the input audio, the size (in bytes) of the compressed file can vary widely.

[jmvalin]

The duration of a file (for encoding or decoding) is a tools issue, not something that libopus can do anything about. Would be better to file your bug against the tools you're using.