How does Adobe encode/compile marker data into the MP3 file?

Report · Apr 15, 2022

Hey there! I am wondering if anybody knows how Adobe encodes marker data into mp3 files.

I used Python's Pydub libray to look at all the MP3 information of an MP3 file that has Adobe Audition markers, but I do not see the markers anywhere (see images below). My guess is the markers are compiled into the MP3 and are hidden so only Adobe products can acess them.

Thanks!

Report · Apr 15, 2022

Those aren't any indication of markers - they're just the ID3 metadata that can be stored along with the file. MP3 famously doesn't support markers at all - which is why things like talking books have to be encoded in a different format that does support them, and generally played on special players.

Audition can write markers to an MP3 file that it can open - but when this happens it's decoded into a Wav file - Audition's working format. Markers can be stored with Wav files, but they are appended onto the end of the file. There's even an app that can edit these separately for anybody who needs additional flexibility with them - but the moment you re-save your file as an MP3, they all disappear - because MP3 simply doesn't support markers.

Report · Apr 15, 2022

Thanks for the all the information Steve. Sorry if I am misundertanding, but if the MP3 format does not support markers how does Audition appear to access markers purely from an MP3?

I took an MP3, loaded into Audition, added markers and saved the MP3 with "save markers" option checked. When I close/re-open Audition and load in that saved MP3 the markers show up - are the markers stored in Audition's cache if they are not in the MP3?

Appreciate your time!

Report · Apr 15, 2022

Not quite. As I said, MP3 famously doesn't store markers. What it can do though is store relative information in an MP3's XMP Media Management metadata. This takes the form of 'derived from' information, and in this case it looks at the file you entered the markers in (which was a wav file, so it supports them) which is referred to as the 'original document' and notes some history entries, which it stores as Resource Events.

So they aren't markers as such - they are just interpreted as markers as long as you open the MP3 file in the (late) version of Audition you created it on. If you try opening the MP3 file in an earlier version of Audition - like Audition 3, or Audacity, or pretty much any other software you can think of, it may see the references and document ID in the metadata, but it cannot interpret them - this is unique to later versions of Audition. You will find all this information in Audition's Metadata screen, under XMP>Media Management but the Resource events don't have readable times on them - they just refer to the file that had the markers in, and just note that 'something' happened at that point. The information is cumulative, and reveals what version you made the changes in. But there's nothing else you can do with the information, I'm afraid. And I have to say that it would make a lot more sense if it didn't re-interpret this as markers - because it fools people into thinking that it's doing something that it really isn't.