Regarding AE exposure time settings

[Naoki.Nishimura]

Hello. I have a question about the “min_exp_time” and “max_exp_time” in the device tree.

I am using Jetson Xavier NX r32.6.1.

I have created a device tree for an image sensor with multiple operating modes and performed verification testing.
As an example of the mode settings, let’s say it is described as follows:

mode0 {
    ...
    min_exp_time = "14";
    max_exp_time = "8333";
    ...
};
mode1 {
    ...
    min_exp_time = "18";
    max_exp_time = "16666";
    ...
};
mode2 {
    ...
    min_exp_time = "22";
    max_exp_time = "33333";
    ...
};

In this case, I execute the following command:

gst-launch-1.0 nvarguscamerasrc sensor-id=0 sensor-mode=1 ! "video/x-raw(memory:NVMM), framerate=30/1" ! nvvidconv ! videoconvert ! ximagesink

I expected the AE control range to be 18 to 16666 [us], but the actual behavior was 22 to 8333 [us]. This behavior was the same even when starting with mode0 or mode2.

For example,

gst-launch-1.0 nvarguscamerasrc sensor-id=0 sensor-mode=1 exposuretimerange="18000 16666000" ! "video/x-raw(memory:NVMM), framerate=30/1" ! nvvidconv ! videoconvert ! ximagesink

did not change the behavior.

However,

gst-launch-1.0 nvarguscamerasrc sensor-id=0 sensor-mode=1 exposuretimerange="16666000 16666000" ! "video/x-raw(memory:NVMM), framerate=30/1" ! nvvidconv ! videoconvert ! ximagesink

resulted in the control being applied within the range of 18 to 16666 [us].

Is this behavior due to the AE specifications, or is it a problem with my device tree configuration?

[JerryChang]

hello Naoki.Nishimura,

it’s known issue that Argus is using the smallest of the max_exp_time property out of all the modes. that’s due to we’ve initialize AE limits after iterating through all sensor modes.

so,
it’s currently not supported for allowing per-mode exposure time settings.

[Naoki.Nishimura]

Thank you for your quick response.
I understand the current specifications.