[mambodog]

Interestingly the N64's RSP has some instructions specifically intended for implementing MPEG decoding (ctrl+f for "MPEG"in http://ultra64.ca/files/documentation/silicon-graphics/SGI_N...)

[giovannibajo1]

Yes unfortunately they're very specific of MPEG1, so they're not really useful for other codecs in the MPEG family. I'm not using them in my H264 implementation (see sibling answer).