D435i Low Framerate when using 2 or more USB-Cameras about librealsense

[MartyG-RealSense]

Hi @Starblazer75 The impression that I get from the code is that when there are two cameras attached the script cannot distinguish between them as separate RealSense and non-RealSense devices.

The RealSense SDK is able to access RealSense and non-RealSense cameras simultaneously if the non-RealSense camera is designated as a Platform Camera. You can test this in the RealSense Viewer tool when both cameras are attached by clicking the Add Source button at the top of the Viewer's options side-panel and selecting the USB camera from a menu drop-down.

If the USB camera is successfully recognized by Add Source then you can display the RGB streams from the RealSense camera and the non-RealSense camera side by side.

There are not many examples of implementing Platform Camera recognition in Python though unfortunately, other than some code from a pyrealsense2 device handling script called realsense_device_manager.py that determines whether or not the camera is a Platform Camera by reading the identification name of the camera to see whether it contains the words 'platform camera'.

https://github.com/IntelRealSense/librealsense/blob/master/wrappers/python/examples/box_dimensioner_multicam/realsense_device_manager.py#L45

[Starblazer75]

When I try turning on any stream of the Platform Camera on realsense-viewer, it gives this error:

30/04 15:28:48,689 INFO [129723605150912] (synthetic-stream-gl.cpp:80) Initializing rendering, GLSL=0
30/04 15:28:48,689 INFO [129723605150912] (synthetic-stream-gl.cpp:89) 0 GPU objects initialized
30/04 15:28:48,729 INFO [129723605150912] (context.cpp:336) Found 2 RealSense devices (mask 0xff)
30/04 15:28:48,746 INFO [129723605150912] (rs.cpp:2697) Framebuffer size changed to 1850 x 1016
30/04 15:28:48,746 INFO [129723605150912] (rs.cpp:2697) Window size changed to 1850 x 1016
30/04 15:28:48,746 INFO [129723605150912] (rs.cpp:2697) Scale Factor is now 1
30/04 15:28:49,040 INFO [129723605150912] (context.cpp:336) Found 1 RealSense devices (mask 0xfe)
30/04 15:28:49,775 WARNING [129722531096128] (sensor.cpp:1291) Failed to add Backlight Compensation control for RGB Camera
30/04 15:28:49,783 WARNING [129722531096128] (sensor.cpp:1291) Failed to add Brightness control for RGB Camera
30/04 15:28:49,801 WARNING [129722531096128] (sensor.cpp:1291) Failed to add Contrast control for RGB Camera
30/04 15:28:49,821 WARNING [129722080020032] (messenger-libusb.cpp:42) control_transfer returned error, index: 100, error: Success, number: 0
30/04 15:28:49,829 WARNING [129722531096128] (sensor.cpp:1291) Failed to add Exposure control for RGB Camera
30/04 15:28:49,848 WARNING [129722531096128] (sensor.cpp:1291) Failed to add Gamma control for RGB Camera
30/04 15:28:49,866 WARNING [129722531096128] (sensor.cpp:1291) Failed to add Hue control for RGB Camera
30/04 15:28:49,885 WARNING [129722531096128] (sensor.cpp:1291) Failed to add Saturation control for RGB Camera
30/04 15:28:49,893 WARNING [129722531096128] (sensor.cpp:1291) Failed to add Sharpness control for RGB Camera
30/04 15:28:49,911 WARNING [129722531096128] (sensor.cpp:1291) Failed to add White Balance control for RGB Camera
30/04 15:28:49,912 WARNING [129722080020032] (messenger-libusb.cpp:42) control_transfer returned error, index: 100, error: Success, number: 0
30/04 15:28:49,930 WARNING [129722531096128] (sensor.cpp:1291) Failed to add Enable Auto Exposure control for RGB Camera
30/04 15:28:49,931 WARNING [129722080020032] (messenger-libusb.cpp:42) control_transfer returned error, index: 200, error: Success, number: 0
30/04 15:28:49,949 WARNING [129722531096128] (sensor.cpp:1291) Failed to add Enable Auto White Balance control for RGB Camera
30/04 15:28:53,377 WARNING [129723605150912] (device-model.cpp:437) Exception caught trying to detect presets: cannot parse device name from 'Platform Camera'
30/04 15:29:06,085 INFO [129723605150912] (sensor.cpp:1594) Request: YUYV Color,
Resolved to: YUYV Color,
Segmentation fault

A side note is that I am now using an x86 computer with Ubuntu 22.04, and when running realsense-viewer without sud o permissions, it gives an error that says it failed to set power state. This was a common problem for me, so I just gave the librealsense source file root permissions for it to keep working. Is this a potential problem?

I will keep working on a solution and let you know if I find anything

[Starblazer75]

Turns out to be a USB bandwidth problem. Not sure why some of the other errors were happening, but the specific one that I am worried about works fine when lowering the quality of the frames. Sorry about that, because it was only happening with the realsense camera I didn't think to modify the working cameras.

[MartyG-RealSense]

It's no problem at all. I'm pleased to hear that you diagnosed the problem. Thanks very much for the update!