IMX.35 Video Capture Causing Blank Video output

Martinnike — Wed, 22 Aug 2012 09:22:44 GMT

Hello,

I'm using v4l on an IMX35 based platform, and have seen a sporadic issue when enabling v4l overlay capture causes video output to stop and the result is a blank screen. The blank screen happens when using the VIDEOC_OVERLAY ioctl on the v4l device.

When this happens, I notice that a the SDC_PIX_SKIP is set in IPU_TASKS_STAT (Which is set to 0x2203) It happens mainly on first attempt at video capture, and the frequency is perhaps 1/20 times.

Attempts to stop capture throw up an warning that tasks cannot be stopped (

DMASDC_0_BUSY is set in the IDMAC_CHA_BUSY register, and never seems to go to zero).

- BG plane is being used for Qt graphics.

- FG plane is being used to capture video, but switched around so graphics is rendered on top (I'm using a key colour.)

I see this error as I am using an EOF interrupt to detect if video capture has stopped [Video freeze has been spotted in certain environmental conditions, and Freescale advised us to use the EOF interrupt as a means to check if capture has frozen] (I write a flag into the IMX internal RAM every frame, and check this value in userland and reset the flag. If the flag never gets detected, then I have to reset video capture. In the case when the 'blank screen' occurs the flag is never written and attempts to stop video capture just give the warning.)

I don't know what the relevance of SDC_PIX_SKIP is, as I cannot find it documented anywhere. It seems a bit suspicious that this bit is set, as it appears to indicate some sort of error condition. Does anyone know what this is?

I don't know whether it's relevant, but Linux is booted from u-boot which has a IMX35 fb driver installed. The drivers are mainly the standard v4l drivers, with a new module for an external analogue->digital converter.

Thanks in advance for any help!

Oh, one thing I noticed is that when the v4l driver is a loadable module, the blank screen happened more frequently than if it was compiled into the kernel.

topic IMX.35 Video Capture Causing Blank Video output in i.MX Processors

IMX.35 Video Capture Causing Blank Video output