topic Latency between camera and display in i.MX Graphics

Latency between camera and display

OlivierG — Mon, 17 Feb 2025 08:07:28 GMT

Hi
I have an IMX93 evk card
I tried the following manipulation:
I coded a digital clock with a resolution of 1 millisecond
I filmed this clock with the RPI-CAM-MIPI camera https://www.nxp.com/design/design-center/development-boards-and-designs/RPI-CAM-MIPI
I used gstreamer to display:
gst-launch-1.0 v4l2src device=/dev/video0 ! autovideosink

I took picture of both clock and display (Westland X Windows)
By making the difference between the 2 I have a difference of 100 ms

By measuring the acquisition time with the open CV function
cv::VideoCapture camera(0, cv::CAP_V4L2);
camera >> frame;
I have a time of 23 ms

the difference seems to be due to the display

Greetings

Olivier

Re: Latency between camera and display

pengyong_zhang — Tue, 18 Feb 2025 08:03:33 GMT

Hi @OlivierG

I think you are right, Could you explain more details about your this phenomenon?

B.R

Re: Latency between camera and display

OlivierG — Tue, 18 Feb 2025 08:40:05 GMT

I must precise that the display is done by a MIPI / HDMI converter

IMX-MIPI-HDMI Product Information|NXP

Greetings

Olivier

Re: Latency between camera and display

pengyong_zhang — Thu, 20 Feb 2025 02:01:56 GMT

Hi @OlivierG

So, What are your specific problems right now?

B.R

Re: Latency between camera and display

OlivierG — Tue, 25 Feb 2025 10:17:32 GMT

Latency is due to a CPU rate that is too high (75%) The acquisition is done by an OpenCV function I'm looking for why it consumes so much

Re: Latency between camera and display

pengyong_zhang — Thu, 27 Feb 2025 13:20:23 GMT

Hi @OlivierG

Did you run any other application? or run the top command See which thread has the highest occupancy rate？

B.R