How do I add the "contains: ..." data to an mp3 file?

I am trying to get gmediaserver (v0.13.0-8) to serve all of my mp3s. Right now it sees only a portion of them. I noticed that the "file" command produces different results for the working files than the non-working ones. On a working file I get the following result:

$ file 01\ -\ 2112.mp3 
01 - 2112.mp3: Audio file with ID3 version 2.3.0, contains: MPEG ADTS, layer III, v1, 128 kbps, 44.1 kHz, JntStereo

on a non-working file I get the following result:

$ file 01\ -\ Prowler.mp3 
01 - Prowler.mp3: Audio file with ID3 version 2.3.0

I loaded the non-working file into audacity and exported it into a test folder, and gmediaserver was able to properly identify it. When I run "file" on the exported file I get the following result:

$ file 01\ -\ Prowler.mp3 
01 - Prowler.mp3: Audio file with ID3 version 2.4.0, extended header, contains: MPEG ADTS, layer III, v1, 320 kbps, 44.1 kHz, JntStereo

Does anyone know what the "contains:..." portion of the data is called and if there is a magic command I can use to add this to an mp3 file?

Is this a red herring. Could it possibly be an issue with the metadata container? If so, how do I display the metadata container version used by the file?

Does the string "extended header" have anything to do with it?

If I can find a magic command to add the right data to the file, I could write a script to do it to all of the ones that are not working. If anyone would like a copy of a non-working file, feel free to PM me and I'll get it to you for testing purposes.