Redirecting Captured Video Frames to IPU

[denizdayan]

I am trying to compose capture frames with another frame, but my goal is not to display the resulting frames on screen. I am trying to send the frames via Ethernet. Since I am working on a 1920x1080 video stream, getting camera frames to user-space has a big penalty for my system. So I thought that somehow if I link capture output to IPU task's input, and link overlay frames (from /dev/fb1) to IPU task's overlay paddr, I can perform a zero-copy composition. I looked over some IPU API examples, and it seems that linking can be done by assigning physical addresses (paddr member of ipu task struct). And then I looked over V4L2 capture examples, but I couldn't find a way to access physical addresses of the capture buffers.

How can I achieve this? There are 3 ways to store capture buffers: MMAP, USERPTR and DMABUF. DMABUF method seemed the right one, but I could not find a comprehensive example to understand the method.

And more importantly, is this the right way to approach this problem? Thanks in advance.

[art · Accepted solution]

Yes, the approach you describe is the right one.

The MMAP method seems to be the right one to allocate physical memory.

Some useful information on that matter can be found here:

https://linux-kernel-labs.github.io/master/labs/memory_mapping.html

Have a great day,
Artur

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