iMX6 v4l2 capture 2 buffers queue

edison_fernande — Mon, 26 Feb 2018 18:19:09 GMT

Hi,

I have an application where I have my camera configured with a long exposure and I need to capture one frame and analize it to detect a certain event.

My problem is that, due to the minimum 2 buffers queue that v4l has, when I dqueue a buffer, I get the oldest in the queue and given the long exposure it is too old for the application as I need the frame to be as close as possible to the time I try to dqueue it so my question is.

Is there a way of avoiding this minimum 2 buffers queue? This is, queuing one buffer only.

If not, is there a way of dqueuing the newest buffer in the queue?

Any help will be appreciated.

Regards,

Edison

Re: iMX6 v4l2 capture 2 buffers queue

igorpadykov — Tue, 27 Feb 2018 10:36:07 GMT

Hi Edison

drivers are based on V4L2 Linux standard API specification available at
v4l2spec.bytesex.org/spec and described in Chapter 9 Video for Linux Two (V4L2) Driver

attached Linux Manual. One can check sources in linux/drivers/media/platform/mxc, in particular
mxc_v4l_dqueue() in mxc_v4l2_capture.c

and queue ioctl descriptions on
https://www.linuxtv.org/downloads/v4l-dvb-apis-old/vidioc-qbuf.html

Best regards
igor
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iMX6 v4l2 capture 2 buffers queue

Re: iMX6 v4l2 capture 2 buffers queue