These are the boot params I use:
console=ttyS2,115200n8 root=/dev/mmcblk0p2 rw rootdelay=1 devfs=mount omapfb.mode=dvi:1024x768MR-24@60 omapfb.vram=0:2M,1:4M

Mount some mmc partition with some videos and run:
gst-launch playbin2 uri=file://$PWD/video.avi

Unfortunately I didn't test audio support... sorry.