i.MX8M Plus MIPI-CSI Inquiry.

[daehyeb1]

Hello, I'm developing using i.MX8M Plus.

We want to implement an around view by entering 4 cameras.

(I understand that 8Mplus does not support virtualID, it is MIPI-CSI4Lanex2ch,

I understand that i.MX8quadmax supports this matter.)

Nevertheless, the reason why I want to use 8Mplus is because there is an NPU that does not have 8quad.

So can I input 2-lane instead of 4-lane in mipi-csi 1,2 and use it?

So, can you process the input signals of four cameras?

[daehyeb1]

I thought about how to use usb communication in a different way.

Would it be possible to use 4 usb camera signals in the form of a usb hub and receive them as one usb input?

[joanxie]

unfortunately imx8mp couldn't support 4 camera in the same time,  you couldn't split 4 data lane to 2 two data lane then connect dual camera in one mipi csi port(in fact, you can connect 2 camera in one mipi csi port via switch), but you couldn't run them in the same time, the reason is what you knew already, imx8mp mipi csi doens't have virtual channels

[daehyeb1]

I thought about how to use usb communication in a different way.

Would it be possible to use 4 usb camera signals in the form of a usb hub and receive them as one usb input?

[kef2]

Regarding USB cameras. You could use even 10 or more of them via the same HUB, if total USB bandwidth declared in camera endpoint descriptors could fit available USB bandwidth.

Usually USB camera developers don't care about this aspect and reserve much more bandwidth than is actually required for given data stream, which may lead to just single VGA camera working via the same USB host controller. It heavily depends on particular cameras used.

[joanxie]

yes, you are correct, my answer isn't precise before, you can connect more camera you want, but need to consider the performance, some customers tested dual usb camera on usb 2.0 and usb 3.0, the performance isn't good enough, some issue with higher resolution, if you can accept lower resolution and frame rate, you can try it, depends on you detailed user case, you need share more detailed information of your application

[daehyeb1]

I will use 4 cameras with resolution of hd (1280x720).
I'm going to use one usb hub
Will these configurations be available?

[kef2]

It heavily depends on USB camera models. If you have them at hand, try connecting all 4 for example to Windows PC via the same USB HUB and try playing them all simultaneously. If all 4 play, then practically no reason then couldn't work on your LInux device. Of course your device may be to slow to handle your requirements, but first you should, you should verify your cameras may stream properly simultaneosly via the same host USB controller. 

1280x720 uncompressed UVC video frame takes 1.843.200 bytes. Isochronous USB2 video bandwidth is 24.576.000 bytes per second. Not taking OS reserved bandwidth, it could be up to 13 such uncompressed 1280x720 frames per second. Or up 6FPS for two such cameras simultaneously. With compressed format you may stream more, but as I already wrote, it all depends on how well your camera is made so that it doesn't reserve more USB bandwidth than is actually required. Technically no problems having more than 4 such cameras even with uncompressed format at very low FPS. No problems having the same at moderate FPS but in compressed format. Just try playing your cameras simultaneously on PC and see if you get live video simultaneously from all of them.