This post on the raspi forums suggests that motion can use a small resolution feed from the raspi camera to perform motion detection and then save a larger resolution version of the frame in question. The purpose of this maneuver would be to keep processing time down. Which is something I am interested in since I am running on a Raspi Zero.
Here's the quote:
The clever part of this version of motion is that the Pi's camera feeds low resolution video to the motion detection algorithm - so that the Pi's processor isn't too heavily loaded - and at the same time, higher resolution stills and videos of the detected movement can be saved.
The post goes on to describe the following options for the motion.config file.
width 320 height 188 framerate 4 mmalcam_secondary_buffer_upscale 5 pre_capture 4 output_both_pictures on output_secondary_pictures on target_dir /run/shm snapshot_filename lastsnap picture_filename preview movie_filename %Y%m%d%H%M%S
I have included these lines in my config file but it seems to cause motion to break. The logs describe an 'event' starting but then all activity stops. Like it's getting hung up on something during the image saving process.
Furthermore I can't find any documentation on the options:
Does anyone have any insight on how I can enable this behavior?