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Today's Topics:
1. Re: Tracking bats - how to increase the motion detection
frequency? (tosiara)
----------------------------------------------------------------------
Message: 1
Date: Tue, 23 Apr 2019 11:14:54 +0300
From: tosiara <tosi...@gmail.com>
To: Motion discussion list <motion-user@lists.sourceforge.net>
Subject: Re: [Motion-user] Tracking bats - how to increase the motion
detection frequency?
Message-ID:
<cachtdwr77qnk7b-ye2gtbab6c95_f9if1mpsrdpr5+jw0b-...@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Motion has hardcoded frame rate for motion detection - it is 3 fps
Here: https://github.com/Motion-Project/motion/blob/master/motion.c#L1835
You can try to alter this code and force process_thisframe=1 for every
frame, that should do the trick
On Fri, Apr 19, 2019 at 10:27 PM Andre Zibell <andre.zib...@gmail.com> wrote:
>
> Hi everybody,
>
> I am trying to set up a raspberry pi3 with NoIR camera and motion in
> order to track the activity of bats, so very small, very fast flying
> animals. In the worst case I am pointing the camera just at the sky with
> IR LEDs for illumination. So the event duration is only a fraction of a
> second.
>
> Therefore, to get at least some images from a single bat, I tried to
> squeeze the maximum number of frames out of the camera, by using the
> following control parameters (motion installed via
> pi_stretch_motion_4.2.2-1_armhf.deb). Please feel free to hint for more
> optimization.
>
> mmalcam_name vc.ril.camera
> mmalcam_control_params -md 7
> v4l2_palette 9
> width 640
> height 480
> framerate 90
> threshold 300
> noise_level 32
> disabling despeckle filter
> disabling video file output
>
> With these I get rather constant 90 FPS from the camera, being enough
> for nice "time-lapse" shots. I prefer the Raspberry Pi v1 Camera over
> the v2, since the 640x480 mode of the v2 camera seems to use only the
> center part of the sensor, resulting in a smaller field of view.
>
> Now to my question/issue: using the "text_changes on" command I noticed
> that the number of changed pixels written to the upper corner only
> changes every 30th or so frame, and thus the decision "threshold crossed
> or not?" also only happens every ~30th frame. For my application this
> leads to the following problems:
>
> 1) When this motion detection decision happens when the bat is already
> somewhere within the field of view, I miss the pictures of it entering
> the field of view. I got around this by setting the pre_capture option to 30
>
> 2) When the bat entrers AND leaves the camera field of view in during
> these ~30 frames in between these decision cycles, no event is generated
> at all, and I miss it.
>
> So my question is: is there an option to have the number of changed
> pixels being calculated in shorter intervals, ideally EVERY frame, or at
> least every third frame or so? I am aware this would increase the CPU
> load, but I am trying to minimize it on the other hand by using no image
> processing, no rescaling, writing only jpegs, etc.
>
> Thanks for your ideas and help on this - otherwise the software
> perfectly fits my needs for this application :) Maybe you can hint me to
> the location for this in the source code, so that I can recompile motion
> for this?
>
> Best regards
>
> Andre
>
>
>
>
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