About d:

The ARM is not good enough to play full resolution screen, but the SoC includes a hardware decoder and a version of mplayer that can play 4Mbit/s 768x576 resolution divx/h264 files without skipping frames. We do not have source for this mplayer, so you can use it in the original firmware, or (with some hacks) in Mer. If you do not want to do this, or you have a file with encoding that is not supported by the hardware decoder, you are limited to using the 667MHz ARM11 core. We do have Xvideo driver for Q7, so at least scaling and colour space conversion are ofloaded from the CPU.