Apalis i.MX6 video decode hw acceleration

running the following command on apalis-imx6 3.14.52 plays a video correctly and uses very little processor(~11% of one core, ~2.7% with Irix mode off):

gst-launch-1.0 filesrc location=path/video.mp4 ! decodebin ! autovideosink

Is it safe to assume the GPU is being used to do the decoding? If so where can I find the library handling the hw acceleration? Is there a way to disable the hw acceleration and compare processor utilization?

You’re assumptions are safe.
(To be more precise most of the hard work will be done by the VPU though.)

The imx specific plugins are build from these recipe with the help of libraries from here.

You could uninstall the two packages providing the gstreamer plugins which do the HW acclerated decoding and install the relevant plugins doing the task in SW.