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Category: Computer Vision

Cutting through the smoke with Retinex

Cutting through the smoke with Retinex

This year, most of August was unfit for bike riding due to wildfire smoke in the air. There was a 10 day stretch where the visibility scale reached zero. Standing on the shores at Shilshole, the smoke was so thick that land wasn’t visible across the Puget Sound. I wondered if land was still visible from a digital camera, even though I couldn’t see it. There is an imaging processing technique call Retinex that is used to enhance the dynamic…

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FFMpeg motion detection

FFMpeg motion detection

FFMpeg motion detection offers a way to create videos that are smaller and shorter becuase it only captures changed scenes. This post discussed the topic, https://superuser.com/questions/984841/ffmpeg-remove-parts-without-motion. Here is the command I used based off of this conversation. ffmpeg -i “http://viewr1:viewr1@192.168.6.184/mjpeg/stream.cgi?chn=0” -vf “select=gt(scene\,0.004),setpts=N/(25*TB)” IPCam4_Motion.mp4 The one thing I noticed was the timestamp in the video is being detected as a scene change, this introduces a higher noise floor. I found that my lowest scene value to be .004. This site, http://www.bogotobogo.com/FFMpeg/ffmpeg_thumbnails_select_scene_iframe.php…

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DVR Video from Images Captured from IP Cameras

DVR Video from Images Captured from IP Cameras

Working with thousands of image files captured from IP Cameras can be problematic. I’ve experienced issues with Caja hanging when simply browsing the folders that contain the captured images. To work around this, I compile video with FFMpeg from the image stock into a separate folder. First I’ll create a file list using this command ls /home/local/Videos/Security/IPCam3_20180726*.jpg > /home/local/Scripts/IPCam3_20180726.txt The results will then need to be processed so FFMpeg can use the file as a reference. Before – Not ready…

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