y3egjsk wrote: ↑
Thu Nov 16, 2017 3:50 pm
Thanks 6by9! The max_video_height and max_video_width did not make a difference in the behavior. You should know that with this problem, the image does respond throughout the range of V4L2_CID_EXPOSURE_ABSOLUTE, it is just that the exposure varies thru a much darker range. With my temporary set to h264, the image varies over a brighter range. When using 640x480 mode, things are brighter still, and my workaround is not needed.
It is very helpful to know that 720p (1280x720) is at the top of the default YUYV video threshold. This image is just as bright as the 640x480, and does not need any workaround, either the h264 I used, or the driver load parameters you mentioned.
Since this is for astrophotography, brightness and resolution are important. Switching to 1280x720 is big improvement. I appreciate your answer!
It sounds like we may have a typo then.
If you run "dmesg" to print out the kernel log, loading the V4L2 driver should have logged
Code: Select all
bcm2835-v4l2: V4L2 device registered as video0 - stills mode > 1920x1080
Having said that, playing with qv4l2(*), JPEG appears at 1280x720 appears to be giving a different image brightness to any of the raw image formats at that resolution. Switching up to 1280x960(**) (ie stills mode) appears to give similar results between the two. So something appears to be wrong there, but it'll require a fair amount of investigation to find out what.
I assume you are setting a low frame rate too if you want 1sec exposures. Either that or setting V4L2_CID_EXPOSURE_AUTO_PRIORITY so that AE is allowed to alter the frame rate as required.
(*) one of the standard V4L2 test apps available with apt-get. Uncheck "Use OpenGL Rendering" from the Capture menu to get it to work.
(**) Annoyingly you can't change resolution in qv4l2. Quit the app, run "v4l2-ctl -v width=1280,height=960" (or whatever resolution), and then rerun qv4l2 (remembering to disable OpenGL again).
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