Ach no. Funking around with the bitstream is way overkill for this purpose - the adjustment is basically static in sample terms, and the DSP has a perfectly good built-in volume control. We're talking about adjustments once per second max (limited by GPS data rate), and modifying samples at a 44.1KHz sample rate in order to achieve this is crazy.

Using the volume ioctls as I described above would mean that the display would always show the actual volume (ignoring volboost factors of course). But does that *really* matter?