I've been told most DVR's and recorders use 192 or 448 Kbps AC3, with a sample rate of 48KHz. Supposedly that rate is constant regardless whether you record your DVD at SP speed (2 hours) or SLP speed (6 hours). Is this true? I've been contemplating recording some of the DirecTV radio channels overnight (for later conversion to MP3), and if the audio fidelity is the same regardless of my DVD record speed, then I should go for the six hour setting. Comments?