Time Stretch problem exporting to MP3

[inkwaterc72697461]

Exporting audiobook tracks out of Audition - all are typically around 1hour in length. Each track needs 10 or 12 markers at exact location to mark sub-chapters. These markers are used (in clickable 'link' form) so people can quickly find specific locations in the audio.

In short, the markers are created in Audition, but then don't match after export because the exported file is 20 second(ish) shorter. Like the file duration has been compressed or something.   If I open the exported MP3 back in Audition, the time appears to have corrected itself, and all the markers are in the 'correct' locations. But any web browser or windows audio player, will play that file it its shorter form - so all the markers are always off. 

So... the markers at the beginning of the playback are pretty close, but by the end they can be 15 or 18 or 20 seconds off their mark. Super annoying. 

Any suggestions as to what's going on here? Or how to correct it?

We're using a 32bit-float / 44100Hz mono source, going down to -> 64Kbps mono MP3.

[SteveG_AudioMasters_]

Audition can only use and store markers with Wav files, and even then they aren't a part of the metadata, but added in a small extension at the end of the audio. MP3 inherently doesn't support markers at all.

Everybody who creates audiobooks with chapters uses dedicated software to create the audiobooks, and also dedicated players to play the files on - players that are specifically designed to do this. There are various approaches to creating the files in the first place - one of them is quite devious and 'repurposes' an existing audiobook...

You might want to have a look at this: How to create an audiobook from mp3 files. Note carefully the bit that says:

"The M4A and M4B file formats contain metadata for chapters and bookmarking. Bookmarking allows you to stop listening in the middle of file and come back later to continue listening. MP3 files don’t allow that."

[inkwaterc72697461]

Thanks, I will definately look that up.

[inkwaterc72697461 · Accepted solution]

I solved my issue with Markers not ligning up after exporting to MP3. 

I've accepted that compressed MP3s are going to run slightly faster than the raw file. And that Adobe can't automatically compensate for that with the markers. I get it. So manipulating the audio inside Audition to manually compensate actually works.  Turns out, the marker locations don't move in multitrack mode, but DO move with edits to the waveform.

Heres how I did it:
- I right-clicked the exported file and found the final play length. (Example: 1:06:03 )

- Went into waveform view, in Audition and Effects->time and pitch->"stretched" the entire audio clip to match the output file's time. 

- Exported the markers to text file again, with their new updated locations.  Boom... success. 

Tips:

- It's helpful to do this time shift on the lowest quality setting. It takes a long time to process these time shifts. (10min in my case)
- If you're doing this to a lot of files at once, note the stretch percentage and use that instead of trying to find the final length of each file. Saves a step in the process.