Some Fruit Punch

There is a party tonight at the Puzzlaria Tavern and Ross asked me to get some orange juice and pineapple juice for the Fruit Punch he is preparing. Being already giddy with all the drinks I had had, I tried some mixing of my own. Grabbing the large orange juice jar (lets call it jar O), I added enough juice into the second jar containing pineapple juice (jar P) till its contents were doubled. Then, I poured some of the mixture back into jar O to double its contents.

Fairly sloshed now, I decide a good way to settle matters would be to again pour from Jar O into Jar P to double P’s contents and proceed to do so. At this point I realize there is an equal quantity of pineapple juice in each jar. If Jar P now has one more litre of orange juice than pineapple juice, can you tell this poor muddle-headed soul, how much more orange juice than pineapple juice there is in Jar O?

Help me! The party is in full swing and Ross is getting impatient !!