Replaygain support

[phirestalker]

Would love replay gain support. The subsonic client list is abysmal for iOS and macOS.

[pR0Ps]

As this player just uses jPlayer to play files, adding ReplayGain support to it would probably be pretty difficult.

However, depending on your server-side setup, it may be possibly to apply the volume leveling there instead. For example, in my case, my music library consists almost entirely of FLAC files with ReplayGain information embedded in them which I use supysonic to serve. Supysonic allows you to configure what commands to run to transcode files. I've just set my decode_flac config option to flac --apply-replaygain-which-is-not-lossless --totally-silent -d -c %srcpath. The --apply-replaygain-which-is-not-lossless flag causes the volume adjustments to be baked into the file as it's transcoded. Obviously this exact solution only works for a very specific setup, but maybe it could be adapted into something that works for you as well.