When I want to grab multi-camera data, the vi-output occupies the cpu 100%

Hi, I’m using the samples from jetson_multimedia_api to check my cameras.
The sample which I was using is “12_camera_v4l2_cuda”, and I found an interesting phenomenon.
When I trigger /dev/video0~/dev/video3 simultaneously, the occupancy of “vi-output” on cpu raises to 100% quickly.
When I trigger /dev/video0 and /dev/video4 simultaneously, the occupancy of “vi-output” would not raise and always be approximate 7%.
The occupancy of “vi-output” will block the images update, and I can not get new images.
How can I decrease the occupancy when I trigger /dev/video0~/dev/video3, and I also want to grab images from /dev/video0 to /dev/video5 simultaneously.

Could you give detail reproduce steps here?


Dear @ShaneCCC ,
Thanks for your reply.
Firstly, I comment out the code related to visualization in sample “camera_v4l2_cuda”.
And then, I open 4 terminals to run “camera_v4l2_cuda” separately. I set the “-d” from “/dev/video0” to “/dev/video3” in 4 terminals.
Next, I get high cpu usage caused by “vi-output”.
Finally, I try to use “v4l2-ctl” to check the images are dropped or not. When I use v4l2-ctl to check camera on “/dev/video0 ~ /dev/video3” simultaneously, the usage of cpu is high too, and lots of image are dropped.

Could you boost the clocks to try.

sudo nvpmodel -m 0
sudo jetson_clocks
sudo su
echo 1 > /sys/kernel/debug/bpmp/debug/clk/vi/mrq_rate_locked
echo 1 > /sys/kernel/debug/bpmp/debug/clk/isp/mrq_rate_locked
echo 1 > /sys/kernel/debug/bpmp/debug/clk/nvcsi/mrq_rate_locked
echo 1 > /sys/kernel/debug/bpmp/debug/clk/emc/mrq_rate_locked
cat /sys/kernel/debug/bpmp/debug/clk/vi/max_rate |tee /sys/kernel/debug/bpmp/debug/clk/vi/rate
cat /sys/kernel/debug/bpmp/debug/clk/isp/max_rate | tee  /sys/kernel/debug/bpmp/debug/clk/isp/rate
cat /sys/kernel/debug/bpmp/debug/clk/nvcsi/max_rate | tee /sys/kernel/debug/bpmp/debug/clk/nvcsi/rate
cat /sys/kernel/debug/bpmp/debug/clk/emc/max_rate | tee /sys/kernel/debug/bpmp/debug/clk/emc/rate

Dear @ShaneCCC ,
Thanks for your advise.
I have set the working mode to Max which is mode 0, and boost the clocks,
But, there are still high usage and image data dropped

That’s weird for the 400186200.60 fps ?!
Could you check if each sensor working well while launch individually.


Thank you for your reply.
I have checked all camera are good working individually.
The reason of 400186200.60 fps is lots of images are blocked, and they are send out in a very short period of time.
But when I active a single camera, images will not be blocked.

What’s the BSP version?
Did you verify on latest release J5.1.1?

@ShaneCCC ,thank you
How can I check the BSP version?
The version of jetpack which i am using is 5.0.1-b231.

Check by below command and the latest release is r35.3.1

cat /etc/nv_tegra_release.

Hi @ShaneCCC ,
Here is the BSP version, R35, and version details are in the image

I didn’t see this kind of problem with reference 6 cameras design.
From your configure didn’t looks like bandwidth cause the problem.
Suppose it could be sensor output problem cause the problem.

Well, this issue often occurs after plugging and unplugging USB devices.
Does any other one encounter this problem?

Please upgrade to the latest JetPack 5.1.1 release to see if still can reproduce this issue.

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