how to install camera support for OpenALPR on a raspberry pi

gistfile1.txt

This is a scratchpad for now.
please do not use it for anything...


Status a/o 2016 01 14: alprd will not connect to the mjpeg stream as configured using this tutorial. not sure why.
according to this: https://groups.google.com/forum/#!topic/openalpr/oGgXBGCRYws you need to compile opencv with support
for libavcodec-dev, libavformat-dev, and libswscale-dev . previous tutorial does not include this and may break when 
these are included. going back to test.   


Assumes you have traversed https://gist.github.com/amstanley/9da7febc9a3e3c2228ee and installed openALPR on your PI

Back up your Pi to an image so if you screw it up somehow you can reset to a known point without having to recompile everything:
diskutil list

pick the correct disk to back up. in my case it is /dev/disk2. note that in the command you will refer to this as /dev/rdisk2. 
sudo dd if=/dev/rdisk2 bs=1m | gzip > /path/to/backup.gz

to restore:
unmount the disk:
diskutil unmountDisk /dev/disk2

then restore the image:
gzip -dc /path/to/backup.gz | sudo dd of=/dev/rdisk2 bs=1m 


follow the instructions on the raspberry Pi camera box to physically install the camera
when you power up, you will need to enter setup and enable camera support:
sudo raspi-config

scroll down to enable camera support and press <enter>, follow the prompts to enable, and then reboot the pi

test camera support by taking a picture: 
raspistill -p 100,100,400,400

Set Up the camera to stream mjpeg. to do this follow this tutorial exactly:
http://www.linux-projects.org/modules/sections/index.php?op=viewarticle&artid=14
the steps are: 
curl http://www.linux-projects.org/listing/uv4l_repo/lrkey.asc | sudo apt-key add -

Add the following line to the file /etc/apt/sources.list :
deb http://www.linux-projects.org/listing/uv4l_repo/raspbian/ wheezy main  <- SHOULD THAT BE JESSIE?

sudo apt-get update
sudo apt-get install uv4l uv4l-raspicam
sudo apt-get install uv4l-raspicam-extras
sudo apt-get install uv4l-server
sudo apt-get install uv4l-mjpegstream

restart: 
shutdown -r now

test the uv4l server by going to http://127.0.0.1:8080/stream/video.mjpeg in the web browser.

edit the alprd daemon config:
cd /etc/openalpr
sudo nano alprd.conf

below the line that says '[daemon]' add or edit the foloowing lines to look like this:

; country determines the training dataset used for recognizing plates. Valid values are us, eu
country = us

; text name identifier for this location
site_id = raspberry_pi

; Declare each stream on a separate line
; each unique stream should be defined as stream = [url]

stream = http://127.0.0.1:8080/stream/video.mjpeg
;stream = http://127.0.0.1/example_second_stream.mjpeg
;stream = webcam

; topn is the number of possible plate character variations to report
topn = 10

; Determines whether images that contain plates should be stored to disk
store_plates = 0
store_plates_location = /var/lib/openalpr/plateimages/

; upload address is the destination to POST to
upload_data = 0
upload_address = http://localhost:9000/push/

Save the file, exit and reboot by typing:
shutdown -r now

whent he reatart is complete reopen tthe terminal and type:
alprd -f 
and see if the daemon connects to the stream.

----------------------
note: there is additonal information out the mjpg-stream command line parms that is relevant at http://rpm.pbone.net/index.php3/stat/45/idpl/23775320/numer/1/nazwa/mjpg_streamer

when you are done, reboot before issuing the final command to run the streamer:
raspistill --nopreview -w 640 -h 480 -q 5 -o /tmp/stream/pic.jpg -tl 100 -t 9999999 -th 0:0:0 &

note that the portion of the command where it says 'tl 100' is the time between stills in milliseconds. 
This was generating dropped frames when I ran it, so I have modifed this to 'tl 5000' to generate a frame every 5 seconds

now make it all run automagically:
cd /etc
sudo nano rc.local

at the bottom of the file, BEFORE it says 'exit 0' insert the following lines:
mkdir /tmp/stream
raspistill --nopreview -w 640 -h 480 -q 5 -o /tmp/stream/pic.jpg -tl 2500 -t 9999999 -th 0:0:0 & 
LD_LIBRARY_PATH=/usr/local/lib mjpg_streamer -i "input_file.so -f /tmp/stream -n pic.jpg" -o "output_http.so -w /usr/local/www" &

^O to write the file, ^X to back out
shutdown -r now to reboot

again, test the streamer by opening a browser and going to:
http://localhost:8080/stream_simple.html

Installing the alprd daemon and getting the results
Documents and files: These are the references I found for the next section:
openalprd daemon: http://doc.openalpr.com/alprd.html#open-source-agent
openalprd daemon relies on beanstalkd: http://kr.github.io/beanstalkd/
programmatically accessing beanstalkd requires beanstalkc: https://github.com/earl/beanstalkc
Installing beanstalkd on a raspberry pi: http://raspberrypirobot.blogspot.com/2012/09/raspberry-configuration.html

Install beanstalkd (and all of the rest just to get a Python interface library) for inter-process queue management:
sudo apt-get install beanstalkd

Install PIP (all the rest is to get support for Python):
sudo apt-get install python-pip python-dev build-essential
sudo pip install --upgrade pip
sudo pip install --upgrade virtualenv

Install PyYAML:
sudo apt-get build-dep python-yaml
sudo pip install PyYAML

install beanstalkc:
sudo pip install beanstalkc

add a line to rc.local to start beanstalkd automatically on boot:
cd /etc
sudo nano rc.local

on the second last line, immediately before 'exit 0' add the following line:
beanstalkd &

^O to save, ^X to exit