It is fixed in hardware, so to playback 48khz files we have to use software resampling. The resampling that Dave is using is known not to be particularly good quality, the problem is that higher quality algorithms are either complex to code or patented.

The code used internally within the Rio Car player software is pretty good at resampling, but unfortunately that is not part of the open source side of the Rio Car, so we can't use that.