Normalize audio

[loonies]

When playing tracks some are louder or quieter and I have to reach to volume control quite often. Think about audio filter that will normalize loudness.

Some ideas using ffmpeg

[c-jacquin]

We could modify this lib ffmpeg-normalize in order to use stream/buffer instead of file path and stream the normalized audio via the http api.

[nukeop]

Sounds like it'll be best to think about this after #335 and #342 so we can bundle it correctly on different systems.

[mlucas94]

I would like to start working on this. The ideas and repository linked are enough to get an idea of how to implement it? Or is there anything else I should know about before I start?

[nukeop]

Thanks for offering the help. It's an open ended problem so feel free to approach it however you like. Remember that you'll need a way to bundle the required binaries on all platforms, and probably use the http api (look at how the local library streaming is implemented).

[nukeop]

I removed the "good first issue" tag since it might turn out to be quite complicated.