That does not have influence on the size of the PiP decoder. The 7251 is really a very basic SoC and it comes with limitations.Sounds like these kind of boxes Socs cannot handle full picture PIP.... FOR h7, HD51 and also for the vs1500 this is an alternative mode from the SOC...
Can you explain what are this limitations?
Ex. if i set Boxmode: 12, and set video output in 480p, can i have a full screen pip ? (i need to view a channel but listen audio from another)