maybe you can. you will have to hack out i2s signal from your comp (I don't know if it is possible) and feed it to your dvdp's dac's i2s input. However, I am not sure if your dvdp will even realize that there is signal present at the input, as its fw may think otherwise if there is no dvd being played. Though you can fool it by playing some random dvd.
Give it a try if you have time and patience.