This is a set of programs for recording video continuously from Raspberry Pi camera, and extracting stills whenever there is motion detected. It is intended to run using two computers on the same LAN.
"PiMotion.py" runs on the Pi, recording 30-second segments of 1080p 8 fps video as .h264 from the camera to ramdisk. For each .h264 file, it also writes a .txt file recording the amount of motion detected every 2 frames (1/4 sec).
Separately, the shell script "push.sh" also runs on the Pi, copying each set of .h264 and .txt files on the ramdisc over ethernet to a remote host, then deleting them to make room for more files. Doing this on the SD memory card would be a little slower, and also eventually wear out the flash due to the amount data flushed through over time. This is running about 1 MB/sec on average, which is 86 GB per day (actually less in practice, during the night the camera bitrate drops).
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To make the 128MB ramdisk (on a 512MB Pi) I added this line to /etc/fstab:
'tmpfs /ram tmpfs rw,size=128M 0 0'
When a .h264 file is transferred it uses a large fraction of CPU. If that is a problem, you can rate-limit the ethernet speed and reduced peak CPU% by adding this line to /etc/rc.local:
sudo tc qdisc add dev eth0 root tbf rate 20mbit burst 10kb latency 70ms peakrate 30mbit minburst 1540
I found this to be unneccesary, after I set the main PiMotion.py (or testing version stest2.py) process to run at maximum priority using the util/startmo script.
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"proc.sh" and "batchjpeg.py" run together on the remote host, in the directory where the files are. They convert the raw .h264 files to .mp4 with MP4Box, and then use the 'avconv' program to extract the still frames with motion (marked out in the *.txt logfiles) and save them as jpegs.
MP4Box is easily installed by 'sudo apt-get install gpac' on any Debian-based system. Note I had to compile avconv from the current github source, because the standard apt-get version does not do frame-accurate seeking, which is needed for this application. My version from https://github.com/libav/libav says avconv version v12_dev0-151-g9a03c23
The remote host receiving the .h264 and .txt files is preferably something faster than a R-Pi. I am using a Acer C720 Chromebook running chrubuntu, plus external USB HDD and TU2-ET100 (Asix AX88772) USB-Ethernet adaptor. This system has plenty of performance in this application.
I originally tried this with the Pi simply writing to a remote folder via NFS, but that was not reliable. It may have been delays or buffering issues through the NFS system but the PiMotion video writer would frequently lock up. Writing from the camera to the ramdisk, where a separate process reads them off, works more reliably.
This code is "beta" phase. It has only been tested in one configuration on one system, but has been running 24/7 apart from occasional exposure-setting tweaks for over a month now, without problems. If you install it, you will need to configure the code to suit your setup.
-J. Beale 11 Oct / 29 Dec 2014