How do I get one of the pearls in "Beyond Good and Evil"?

I've tried and tried to get the pearl that's through the "transit" door in Pedestrian's city...I don't have a problem getting through the beams on the conveyor belts until you get to what looks like the last one- only when I get to what looks like the conveyor belt that goes by where the pearl and crates are, it's going the wrong way. I've tried and tried to run up the conveyor belt fast enough to go underneath the first beam before one of the machines comes down the belt, but I can't manage to get past both beams to where I could possibly jump to where the pearl is!! I've finally given up- I've tried quite a few different times, but never manage to do it and it's driving me nuts! Help!