The last macro block of the last frame does not come out of the MPEG4 Part 2 Decoder. Why?
This issue can be resolved by sending 10-20 bytes of dummy data at the end of the frame. The dummy data does not cause an error in the output as it is ignored on restart up until the next VOL/VOP is detected in the bitstream.
See (Xilinx Answer 30157) for a detailed list of LogiCORE MPEG-4 Part 2 Simple Profile Decoder (MPEG-4 Part 2 SP) Release Notes and Known Issues.