Delayed frames income with v4l2 and libArgus

Autonomous Machines Jetson & Embedded Systems Jetson Xavier NX
1

Hello,
I am tracking timings for my incomings frames. I am not doing any processing of frames, but still frames captured come in late (not very often, but it happens). I need to do some time-sensitive operation after I got a frame (what can have -0.5ms/+0.5ms variety, no problem) but I see big jumps, even 3ms.

This happends with v4l2 but also with libargus api.

I tried to set priority with “nice” but it didnt help out on this.
Do you have any explanation and maybe even a solution to this?

I made a graph that shows the timing between the actual and the last frame, which should be around 17500microseconds (since I am using slightly slower fps than 60).

timing-between-frames-microseconds

Best regards,
jb

1 Like
3

Maybe print the SOF from vi5_fops.c to confirm the frame coming consistently.

5

I can confirm that printing sof in vi5_fops.c, the difference in frame income is 2 microseconds max. So at this point, everything works fine. Any idea what can delay frames on the way to userspace?

6

Try boost the system to check.

sudo nvpmodel -m 2
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

echo userspace > /sys/devices/13e10000.host1x/15340000.vic/devfreq/15340000.vic/governor

echo 1 > /sys/kernel/debug/bpmp/debug/clk/vic/mrq_rate_locked
echo 1 > /sys/kernel/debug/bpmp/debug/clk/vic/state
cat /sys/kernel/debug/bpmp/debug/clk/vic/max_rate > /sys/kernel/debug/bpmp/debug/clk/vic/rate
7

No difference. The problem remains. I had most of these settings also on with the original test.
(jetson_clocks and MAXN mode and VIC high frequency)

8

Any ideas on how we can continue? Could you reproduce the problem? Do you see the possibility that this issue is fixed with real-time Linux kernel on the newest Jetpack release?

10

I would suggest try J5.0.2 due to the capture firmware different a lot.

Thanks

11

I found out, that I do not have this problem capturing with MMAP instead of USERPTR. Any idea why? Will test if I can get the same low latency with MMAP as with USERPTR.