Why does the AVC use more memory than the HEVC codec?
See Table 3-9 of (PG252):
This is because AVC requires extra intermediate buffers when it is using multiple cores. The Zynq UltraScale+ MPSoC VCU AVC Encoder uses multiple cores when the resolution is >= 1080p60.
The AVC standard does not support tile processing like the HEVC standard does.
As a result, in order to support the parallel processing when using multiple cores, the AVC encoder requires two intermediate buffers.
This is the reason for the ~100MB delta between the HEVC and AVC CMA requirements for 3840x2160 in Table 3-9: VCU Encoder CMA Requirements in (PG252).