Nice idea! In my opinion, per-song volume adjustment is better than dynamic compression because it preserves the volumes within each song. But a few obstacles come to mind:

1) Getting the info into the tag. Do commonly used rippers/taggers add this info? If not, could I forego the ID3v2 thing altogether and maybe leverage the data Toby uses in the Info:Seek tool somehow? Maybe that's a better approach since it's automatically done by the player anyway? We'd just need to know how to glean the peak volume from his data, if that's possible.

2) Setting the volume. I can send VolUp and VolDown IR codes, but that's yucky. There might be an ioctl() somewhere for me to set it, but I'd have to set it as a percentage of the current volume, or relative to some baseline volume or something... Maybe re-use something that was provided with the volume boost stuff? Not sure if there were userland hooks to that stuff or not.

Otherwise, this might be doable!