Adding dmaiperf in decode (or loopback) pipeline either corrupts video or fails
to init sink. Below pipeline does not work :
... ! TIViddec2 ! dmaiperf ! TIDmaiVideoSink ....
root cause: dmaivideosink supports peer buffer and since dmaiperf is based on
transform class it sends peer alloc request to downstream
and as expected dmaivideosink responds to its event but if padAlloc is not
enabled on TIViddec2 then sink will not able to share the buffer
between TIViddec2 and TIDmaiVideoSink.
soln: like other tranform elements (e.g identity, tividderesizer) implement
prepare_output_buffer function which pushes the same buffer to downstream.