store mp3 preview files (fixes #66)

[ngokevin]

For reliable cross-browser audio previews and to support BeatSaver Viewer on platforms such as Safari/iOS. Went with MP3 over AAC due to Firefox support.

I guess optimally, these things would be done using a task queue, but I think the upload frequency is enough to do it on demand.

Using an exec / shell call-out vs php-ffmpeg because want to do it in background to not hold up the HTTP response.

[ngokevin]

Is anyone open to check this out? Much appreciated!

[Assistant]

Would it be possible to use a dynamic name that matches the current song name rather than a static preview.mp3?
i.e., songName.ogg -> songName.mp3.
Ideally iterating over each difficulty and performing the operation on each if that same ogg file hasn't been converted already.

[ngokevin]

Done! I store it as their original filenames and handles per difficulty.

[Assistant]

@lolPants could you take a look at it as well?

[luludotdev]

I'll check it out later today

[ngokevin]

@Assistant Also, are you handling the script for retroactive conversions?

[Assistant]

I can handle it, however I can't promise I'll be fast since I have a lot on my plate currently. If you want to help with it, that'd be welcome too.

[ngokevin]

Sure. What kind of environment is it? Do I just need to write a script that manually runs in the storage directory?

[ngokevin]

So good to go? I can write like a Node script that does the conversions in a queue if that sounds good.

[ngokevin]

Sorry to bump this (also thanks for testing the spaces in paths!). Anything else to do after the PR gets approved?

[sinfuljosh]

Since this is still a thing.... has anyone thought about using https://github.com/brion/ogv.js/

It’s the same setup Wikipedia uses to play ogg files one iOS