topic Re: How to increase video performance from camera source on i.Mx35 ? in i.MX Processors

How to increase video performance from camera source on i.Mx35 ?

kaieckardt — Thu, 15 Aug 2013 09:06:44 GMT

Hello everyone,

we use an i.Mx35 and have to display a video from a camera without wasting cpu cycles. There are two examples provided in freescales BSP CAMAPP and TVIN. Both use DirectDraw and overlay to show the picture. But they still use a memcpy() to copy every line seperate into the overlay buffer.

from CameraWindow.cpp line 671 in CAMAPP example:

            // If height in bmiHeader is negative, the image is top-up, we just copy it.
            // Or esle the captured image should be bottom-up, so we vertically flip the image.
            if(pCamWin->m_PreviewDataFormat.VideoInfoHeader.bmiHeader.biHeight < 0)
            {
                for (height = 0; height < displayHeight; height++)
                {
                    memcpy(pbyDstBuffer,pbySrcBuffer,(displayWidth * pCamWin->m_ibiBitCount) / 8);

                    pbySrcBuffer += (pCamWin->m_DisplayInfo.imageWidth * pCamWin->m_ibiBitCount) / 8;
                    pbyDstBuffer += (displayWidth * pCamWin->m_ibiBitCount) / 8;
                }
            }

can anyone tell me if it is possible to do this using dma or another cpu cycles saving technique ? An example would be great..

best regards,

Kai

Re: How to increase video performance from camera source on i.Mx35 ?

Yuri — Mon, 19 Aug 2013 08:01:48 GMT

I am afraid the using memcpy() function is most suitable approach, assuming

that memcpy() is highly optimized.
Next, I do not think that SDMA using provides improvements in comparison

with standard memcpy() function, which applies ARM instructions LDM/STM.

And SDMA-based design will require additional efforts.

Re: How to increase video performance from camera source on i.Mx35 ?

kaieckardt — Thu, 22 Aug 2013 10:02:13 GMT

So as the IPU has an own DMA controller... is there no chance to simply configure the IPU to do the job without occupying the cpu ? ATM we use WinCE 6 (with an ARM4 compiler). So a memcpy will not use the latest arm instructions.

Re: How to increase video performance from camera source on i.Mx35 ?

Yuri — Wed, 30 Oct 2013 04:35:58 GMT

I am afraid we do not have an example (just) for memory-to-memory copying via the IPU.

Re: How to increase video performance from camera source on i.Mx35 ?

kaieckardt — Tue, 10 Dec 2013 10:22:38 GMT

This topic is still not solved. I need an example for a simple memory to memory dma transfer using windows ce6.