DirecTiVo has no MPEG2 encoder like the SA models. DirecTiVo records the bitstrem directly from DirecTV's satellites. This means it is a perfect bit-for-bit digital copy of what your dish receives from DirecTV.

The recording time on the DirecTiVo box is stated as "about 35 hours" because it depends on the compression rate DirecTV is using for each channel. I know of people getting 40 hours on a DirecTiVo and some getting 20 hours. It all depends on what you're recording.