Bit Rate Limitations for CSI?


I am troubleshooting issues with streaming 2x 4K image sensors. Currently I have the sensors configured to use a 1440Mbps lane rate across 4 lanes each. More often then not (4 out of 5 times), when streaming both sensors at the same time, one sensor will error out with nvarguscamerasrc and I will se tegra-vi errors with dmesg. When I boost the nvcsi, vi, and isp clock speeds for debugging my issue seems to go away. This leads me to believe that I may be running into upper limits on data rates. Is this the case? Is there documentation for guidance on these speeds?

Thank you,

hello joe_kale,

please check developer guide for the Software Features.
dual 4K camera sensors running simultaneously has only validate on Xavier series.

you should also access Jetson TX2 Series OEM Product Design Guide, each data lane has a peak bandwidth of up to 2.5Gbps, the max CSI bandwidth is 30Gbps, (i.e. 2.5Gbps/lane * 4lane/brick * 3brick)
for your sensor pixel rate calculation, please also consider 15% protocol overhead.
here’s an example for CSI data rate calculation, assume it’s a 4K@90fps,10-bit camera sensor,
i.e. 3840x2160@90-fps,10-bit = 3840* 2160* 90* 10 *1.15* (15% protocol overhead) = 8584704000 ~= 8 Gbps.

hello JerryChang,

Thank you for the response. My sensors are only streaming at 30 frames a second so my combined rate of both sensors is only ~7Gbps (including protocol overhead). We have previously used this sensor streaming 2 simultaneously in Leopard Imaging development kits with no issue, but their data rate was set to 891Mbps.

I forgot to mention that I am using a TX2 NX. Is there any difference in ability between how the TX2 chip functions between the 2 SoMs?

hello joe_kale,

CSI bandwidth is remain the same between TX2 and TX2 NX.
however, we’ve not validate the use-case for dual 4K camera sensors running simultaneously on TX2 NX.

you may have a try,
please refer to Jetson/l4t/Camera BringUp - to boost the clocks if you’re having stability issues.

hello JerryChang,

Boosting the clocks seems to make the stability issues go away.

Is this a recommended change to support the sensors?
Is there a way to make these changes permanent with the pinmux settings?
Are there any drawbacks to pushing those clocks to their max rate?

Thank you

hello joe_kale,

as I mentioned previously, we have never validate the use-case for dual 4K camera sensors on TX2 NX.
so, please do have workarounds for your solution, you may also have scripts to configure clocks internally.

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