Is there a way to get large thumbnails of videos I have posted from Facebook?

I'm trying to get large video thumbnails via FQL or the Graph Api.

When I request a thumbnail I get:

vthumb.ak.fbcdn.net/hvthumb-ak-snc4/hs1270.snc4/158204_144210235636391_144209442303137_10056_685_t.jpg

I randomly noticed today though that if you change the last t to a b you get:

vthumb.ak.fbcdn.net/hvthumb-ak-snc开发者_如何学运维4/hs1270.snc4/158204_144210235636391_144209442303137_10056_685_b.jpg

When I tried another older video I got:

vthumb.ak.fbcdn.net/vthumb-ak-sf2p/v33376/20/15/508029674/t508029674_402635544674_1192.jpg

The position of the t is different but if I switch it out to a b I get:

vthumb.ak.fbcdn.net/vthumb-ak-sf2p/v33376/20/15/508029674/b508029674_402635544674_1192.jpg

My question is switching the last t to b a reliable way to get large FB video thumbnails? This certainly isn't documented anywhere that I found. Is there any other way to get this link from FB reliably?

Thanks,

p.s. sorry for not posting images or links, i dont have enough reputation points.

they have many undocumented features. For now it works, so far so good. Set an error flag, and when the time comes and facebook does not respond to your hacked query, you can find a new way. I would not bother for long time issues. Facebook documentation is a mess, make the best out of it. btw, make sure that the error message gets you and makes itself noticed. do not forget to add some code to degrade gracefully. show the potential users another placeholder picture when the query returns no picture.