What I don't get is why Infuse is the only player that rejects pure audio files. All others can play them, not this one. I just did the following for one album I have:
1 - First of all, all files are FLACs, not MP3s.
2 - Used an image and with Photoshop I added a text saying "Track 1: X", saved the image. This for each one of the 21 tracks.
3 - Opened Sony Vegas, added one FLAC and one image, removed the audio and saved only as .mp4 (only the video, but with the same length as the audio. I don't want any reencode).
4 - Used MKVToolnix and added both the FLAC and the MP4. Saved as .MKV. There is no reencode, according to the thread from the software, from Doom9.
After step #4, Infuse can readily recognize everything, the video is played while the audio can be heard.
However, to do all of this to countless tracks would take A LOT OF TIME.
And I must say that it takes a lot more disk space. For example, track #4 is wasting 31 MB for the video alone, saved as 4:3 (480p = 640x480), and 21 MB for the FLAC. Considering that FLAC already wastes more disk space than MP3, do the math and you'll see how this isn't ideal by any means.
BTW, I tried adding a FLAC to MKVToolnix and saved as .MKA (Matroska Audio). Infuse can't recognize. When I renamed the MKA to MKV, it could, but if you fast-forward at any moment, the playback stops immediately. This is only useful if you plan to listen from start to end.
I know Infuse is focused on videos, but no one these days use a 2nd player for audios only. Not even in my PC I use Winamp or similar software anymore, I rather use Media-Player Classic (or VLC) for all contents. The only exception are Blu-ray discs, then I use DVDFab Media Player. Still, this player is only useful if I want to see menus and some contents that can't be converted to MKV (and that require the authored disc to be played).