Clarify Replay Gain specification

[khers]

I have a user whose library contains files tagged for replay gain and it is exposed through his Open Subsonic server. However, the project I am working on only supports the EUB R128 specs for perceived loudness. Up front, I am not an audio person and the details of the differences between ReplayGain 1.0, ReplayGain 2.0, and EUB R128 are not clear to me, especially how the three specs relate to each other. However, I believe that it is not possible to use RG 1.0 values in a system that implements either RG 2.0 or EUB R128 (but it may be possible to convert between RG 2.0 and EUB R128, please correct any of these assumptions if they are wrong). What specification is intended with the ReplayGain response type?

[Tolriq]

This was not really managed at that time.
I guess most servers just report the data from the tags and so for anything but Opus it's RG2 and EUB for Opus.

Technically this does not change a lot it's just the reference / target Db that changes, and it's easy to normalize (but client needs to offer the choice to normalize toward what).

You can add a PR to add a new field that explicit the type of RG data.

[khers]

Thanks, I have created the PR.