Replaygain tracking during playback

[Vchat20]

This is one thought that has crossed my mind. A few PC based players I know have the option where if a playing file doesn't have RG tags, it'll compute them as it decodes and plays the file and embeds it once done.

I don't have any idea of the implications of the function. And it's kinda hard to guess what the resource usage would be like when trying to compare against the PC either via standalone RG calculation or calculation on these players during playback. But curious what the feasibility is for this kind of function in rockbox?