8PSK
From MythTV Official Wiki
8PSK (8 Phase Shift Keying) is a modulation method. It is basically an extension of the old QPSK modulation method to use eight states rather than four. This requires slightly more DSP cycles but allows more data to be transitted in the same bandwidth.
Other modulation methods include QPSK, QAM, 8-VSB and COFDM
