Some mp3 files won't play in some players

[oubliette]

I have a set of mp3 files that won’t play using PlexAmp on iOS, PlexAmp on macOS, or the Plex app on AppleTV, but do play through the Plex web interface/client. (I also suspect these mp3 files of causing library radio playback via Alexa to stop abruptly, but I can’t prove it.)

The symptoms differ slightly per player, PlexAmp on macOS briefly displays “couldn’t start playback”, PlexAmp on iOS brings up the play sheet and then dismisses it, Plex on AppleTV “thinks it’s playing” - computes and displays a “soundprint” but makes no playback progress and produces no audio.

I’ve tried re-encoding the files, no change (they’re compressed using Lame from FLAC originals, which play correctly).

PMS: 1.21.1.3830-6c22540d5 (linux)
PlexAmp macOS: 3.4.0
PlexAmp iOS: 3.4.0
Plex tvOS: 7.11 (22422)

Any suggestions to diagnose would be appreciated.

[oubliette]

I couldn’t get much out of the PlexAmp logs, but I saw a message of the form:

Dec 25, 2020 13:42:52.590 [0x120f7000] ERROR - BASS: Error [ret = BASS_StreamCreateFileUser((DWORD)STREAMFILE_NOBUFFER, flags, &proc, context)] - 41

41 is BASS_ERROR_FILEFORM which led me to look carefully at the file(s) that wouldn’t play.

I think the playback engine (BASS - https://www.un4seen.com/) used is particularly intolerant of files with stream synchronization errors.

most other players play the my test file correctly, but mp3val (http://mp3val.sourceforge.net/docs/manual.html) reports:

Analyzing file "....mp3"...
WARNING: "/path/to/....mp3" (offset 0x280a): MPEG stream error, resynchronized successfully

I re-encoded the file (most of my library is encoded from FLAC rips) - mp3val no longer reports an error, and once the PlexAmp cache is cleared the file plays.

I was looking for a desktop player that uses the same playback library to see if I could confirm my theory, but haven’t so far.

[oubliette]

inconclusive but promising data for others who may find this thread:

I re-encoded mp3 files for which I have a flac original, and for those affected mp3’s I don’t (e.g. purchased tracks) I allowed mp3val to “fix” the files.

Since doing so (and confirming mp3val reports no errors), library radio playback has been reliable, both on AppleTV and via Alexa.