MPEG4 encoding is not supported at all on the Pi due to licence costs. (IIRC the hardware only supported up to 720P30 anyway)
H264 encoding is supported on all variants of the Pi, and is specified to run at up to level 4.1 (1080P30) although it can be overclocked to get a bit more out.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.