Handle and ignore invalid bpm values in MP3 files

[uklotzde]

Fixes https://bugs.launchpad.net/mixxx/+bug/1832325

Actually caused by an ugly workaround to adjust non-standard bpm values.

[daschuer]

Good catch. LGTM.
Waiting for CI

[uklotzde]

Looks like util/fpclassify.h is incomplete and not portable :((

[igor47]

fun fact: my laptop was stolen and i was re-setting up mixxx on a new one. i had an unexpectedly out-of-date backup of .mixxx (already bad, i lost about two years of cue points, stars, plays, and crates), but trying to use it resulted in pegged CPU and unresponsive UI. i then spent about 8 hours trying various things. eventually, working on the assumption that it was the large number of files in my music library that was causing the problem, i moved a bunch of directories out, and was moving them in one letter at a time (like mv a* ~/Music/music) and re-scanning the library. this allowed me to eventually zero in on certain specific files that were not working.

really appreciate the speed of resolution here, since i am hoping to use Mixxx at an event this weekend and some of my files cannot be added to the library.

[igor47]

confirmed that applying https://github.com/mixxxdj/mixxx/pull/2157.patch fixes all my problems

[uklotzde]

Oh, no. The plugins failed to build!! I have to find a workaround for 2.2 without using fpclassify.

I will revert all changes and force push this branch when finished.

[uklotzde]

I found a solution that doesn't need the fpclassify workaround and hopefully works on all platforms.

[daschuer]

Nice solution. LGTM.
Waiting for CI

[uklotzde]

@igor47 Thanks for tracking this down, reporting, and providing the example file! The supply of malformed and corrupt files is endless, there is always a new edge case that has not been covered yet.

If you enable metadata export Mixxx will replace the invalid ID3v2.3 tag with a fresh and valid ID3v2.4 tag.

[mbrouillet]

I built from source today, and "Rescan Library" does no longer hang. Thank you !