ASI for LP input (Low priority) and 2 ASI for HP (High Priority).
fact that you have 2 for both HP and LP is just a redundancy: In
of failure of one input, you can use the other one.
Now, what means HP and LP?
Actually, this is for what is called
hierarchical mode: On HP, incoming TS will be modulated at low bit
(for DVB-H stream typically) and on LP, TS will be modulated at
rate (DVB-T streams). This is thus a way to transmit DVB-H and DVB-T
streams at same frequency.
On HP, modulation is at low bit rate since the information required
display on a handset is much smaller than the one to display on
screen. But the modulation on HP is much more robust compared to