We need the mobility of the Tegra platform. The desktop GPU test was mostly a proof of concept that (wrongly) assumed code could be ported, but also proved the hardware is capable.
Meanwhile doing some more testing on Tegra, setting I frame and IDR frame interval to 2, and using the motion reporting, it seems we can achieve similar results.
However, as stated earlier, setting V4L2_CID_MPEG_VIDEO_H264_8X8_TRANSFORM seems to have no effect on the reported motion vectors (nor does it generate any errors). In the same way setting V4L2_CID_MPEG_VIDEO_MPEG4_QPEL to 1 also seems to have no effect on the reported motion vectors. Am I missing something ?