Which console do you have? the 'Phat' , slim, or new 'super slim'? You can on a hacked / JB PS3 on the older consoles - most of the firmwares offer it (or they did last time i looked). Is 4.46 the latest? if genuine FW then I dont think you can. PS3hax.net used to be an invaluable resource, maybe worth a look

Pretty sure you can sort it another way too through re-encoding them but not sure off top of head - I'm sure some far more nerdy people will be along to help