Can the post processor in the i.MX8m Hantro decoder be used?

[crg7475]

I noticed that the Hantro decoder in the imx-vpu-hantro package seems to be disabled, since in the Makefile_G1G2 file, the ENABLE_PP macro is not definef.

Is there a reason for this? Being able to do postprocessing with the VPU sounds quite useful, for example for downscaling decoded frames prior to further processing it if only small resolution is needed (one example use case would be some sort of object recognition processes that don't need lots of pixels).

[jamesbone]

The imx-vpu-hantro depends on ION memory allocator APIs which became obsolete after kernel 4.12.

It seems that these kernel APIs were changed after 4.12 to use a dma buffers similar to the V4L2 APIs.

The Hantro video decoders are not unique to the i.MX8M.  They are also in several Rockchip designs and as such a common driver stack is being developed that works regardless of the SoC being used.  This stack will likely leverage the V4L2 API.  You can see some work down this path at the following URL:

[PATCH v2 0/9] Rename Rockchip VPU driver to Hantro, add initial i.MX8M support

There was a customer who successfully replaced the driver solution with the V4L2 implementation from Rockchip.

https://www.mail-archive.com/linux-media@vger.kernel.org/msg147671.html

There are plans for using V4L2 interface for controlling the Hantro VPU, but it will be based on the VeriSilicon driver and we don’t have a public roadmap as of today.

There are no plans for the moment to use DMABUF instead of ION in imx-vpu-hantro.

[crg7475]

So, the reason why the post processor is not enabled is simply because not much development is being done on the imx-vpu-hantro package?

Note that imx-vpu-hantro still works, even with kernel 4.19. Also, I know about the V4L2 mem2mem efforts, that's not my question. My question is why the postprocessor in imx-vpu-hantro wasn't enabled.

[jamesbone]

Yes, the reason basically it is related to software development, since most of this libraries are directly provided by Hantro.