D435 control RGB module speed
Hi,
We are using the D345 camera in an outdoors project and we are facing issues with the RGB module. We are using the auto-exposure setting and requiring the camera images with a resolution of 720p at 15 FPS (as for our application we don't need more frames). The camera is mounted on a vehicle that moves at 5 km/h. With this setting, even with sunny days we are getting blurred images and we started wondering if we could get the camera information.
1. The first and foremost problem is that we cannot access the real exposure-time and gain when auto-exposure mode is enabled. We've seen some "old" posts that say it isn't possible. Is there, currently, any way we can access it?
2. Since the problem appears to be in the exposure time, we wanted to know if it would be possible to limit the exposure time and gain when the auto-exposure is enabled. We've seen the setting that allows to prioritize the frame-rate to the exposure time. However, it is counterproductive to flood the system with data (by asking the camera to provide, for instance, 60 FPS if we only need 15 FPS) because we also require the other images available (ir and depth) and the USB doesn't have that much bandwidth. So the question is: is there a way to set a maximum exposure time when auto-exposure is enabled?
Thank you for your time!
-
1. Exposure and gain values do not update whilst auto-exposure is enabled. You can though get the actual values from the camera's metadata. When auto-exposure is turned off, the camera reads the last known manual values. You could then switch auto-exposure back on after the values have been updated. Details about using metadata to get exposure and gain values after auto-exposure is turned off can be found here:
https://github.com/IntelRealSense/librealsense/issues/1624#issuecomment-389085387
Metadata support is enabled by default on Windows, and needs to be patched in on Linux.
2. When auto-exposure is enabled, you can avoid the risk of FPS dropping if exposure exceeds the FPS period by disabling the "Auto-Exposure Priority" control to enforce constant FPS.
-
Thanks for the quick reply!
Regarding the point 1, we'll try the proposed solution.
With respect to the second point, we know about the "Auto-Exposure Priority" control. However, what we would like to be able to do is the following:
Suppose we compute that the maximum exposure time to avoid blurring given our conditions is 20 ms, however, with the camera working at 15 FPS, using the "Auto-Exposure Priority", the maximum exposure time would be saturated at 67 ms. To achieve what we need, we would have to set the camera to 60 FPS (17 ms). However, because of the usb bandwidth, we cannot do this. So we would like to tell the camera: saturate the exposure time to 20 ms independently of the FPS.
That's how we feel the "Auto-Exposure Priority" control should work. In this way, you can tune accurately the camera performance independently of the video.
Could this be done somehow?
-
I have carefully thought about the problem and cannot think of a way to reduce blur with the SDK when auto-exposure is enabled except to use a high FPS. An alternative might be to try using 30 FPS and dropping the resolution to 640x480 to reduce the amount of data generated.
I would speculate that you could cap the exposure externally by putting some kind of physical device on the camera. This could include an external shutter, a custom material to cover the imagers in place of the default transparent material, or applying a micro-thin filter film over the camera's IR imager to limit the amount of light that can enter the camera. All of these should alter the properties of the light entering the IR sensor.
Given that you are only moving at 5 mph, I wonder if a D415 camera instead of a D435 might help. Its IR imager is less wide than the D435's and so lets less light in. Although the D435 excels at tracking motion due to its global shutter, 5 mph may be slow enough for the D415 to cope with without motion blur occurring, since it can usually cope with human walking-pace motion without problems
Please sign in to leave a comment.
Comments
3 comments