Dedicated SBC Camera Monitor

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A guide to setup an SBC (Beaglebone black) or Desktop that will monitor a video feed from ZM. Simply add power, and the video feed will appear on boot.

OS will be Devuan Jessie, WM will be dwm, terminal st, and browser will be surf. It will be a minimal installation. Leaner than LXDE, the default DE for beaglebone.

I'll include optional steps to setup Device Trees and the I2C peripheral (Beaglebone specific) and read a sensor. Combine with ZMTrigger.

This is noticeably more difficult than connecting a coaxial cable to a CRT such that an analog, older setup would have. But is more flexible. A desktop is generally recommended here, but SBC's can be used as well.

After you setup this OS once, it's advisable to copy to an img and then deploy on as many machines as necessary. A good size for the single OS root partition might be 4GB.

Tested in 03/2017 on a Desktop and Beaglebone with Devuan Jessie

Note that in the end, due to faulty video display, I ended up using an old laptop instead. A BBB is able to handle one stream, but seemed to have a bug in the final deployment.

Update: 08/2018 Tested with Rpi3 and Debian Stretch migrated to Devuan Ascii here Dedicated_RPI_Camera_Monitor

Another companion to this guide is the Desktop_SBC_Camera_Monitor

11/2018: See also Zoneminder Blogspot - ODroid XU4 Zoneminder Client guide.

Setup

Installation

Requirements

  • At least 4GB SD
  • SBC / Desktop / Laptop
  • Internet connection
  • Computer monitor
  • HDMI cable for BBB (I use a HDMI to DVI adaptor)

Install Beaglebone Black Debian Jessie using elinux.com's BeagleBoardDebian page.

Use the direct image (under Demo, below NetInstall). Not the netinstall, which is slower, unless you know what you are doing.

After booting from the SD card, make sure the network interface is set to load in: 

nano /etc/network/interfaces

Next, migrate to Devuan using Dev1fanboy Upgrade-Install-Devuan wiki guide. Skip most of the part about the display environment. Reboot after apt-get dist-upgrade. Try the purge of libsystemd0 in DE section, if you like. May not work. RCN repo seems to want it.


Complete the following commands 

 su root

Remove non-free from /etc/apt/sources 

 nano /etc/apt/sources.list
 apt-get install xorg libx11-dev libxft-dev libxinerama-dev gcc make htop sudo tcpdump git

For Surf 

 apt-get install libwebkitgtk-dev libgtk2.0-dev linux-headers-$(uname -r)

Download simple programs 

 git clone http://git.suckless.org/dwm && git clone git://git.suckless.org/st && git clone git://git.suckless.org/surf

Edit the config for dwm 

 nano dwm/config.def.h
  • Later Disable the bar
  • Later Remove all workspaces except for 1 (*tags)
  • Set Mod4Mask as modkey (redmond key)
  • Set MODKEY|Shiftmask to 0 and XK_c to XK_F12 for killclient (personal preference)
  • Later disable spawm of dmenucmd and termcmd, but for now leave enabled.
cd dwm
make
make install
cd ../st
nano config.def.h
  • Set termname[] to xterm (resolves some issues with programs that don't understand default termname).
make
make install
cd ../surf
nano config.def.h
  • Review options
  • Later set runinfullscreen to TRUE
  • Later set kioskmode to TRUE once debugging is over
make
make install

Cleanup

apt-get remove nfs-common rpcbind wpasupplicant avahi-daemon ofono apache2

Leave wpasupplicant if you use wifi. Net installer may want to install acpid. Beware of removing cron. Just disable the service. Remove Exim4 if you want.

At this point maybe 40MB RAM, and <5% CPU. Compare to LXDE.

Clock

Only needed if you are keeping time. 

# apt-get install openntpd

You can run ntpdate for manual updates but an ntpd daemon seems to run better (albeit, it opens ports and uses more resources).

Auto Start

Edit .xinitrc, /etc/rc.local, /etc/inittab, and .bash_profile to auto startx without requiring a login, load surf with the path of the zm server monitor feed, and disable the screensaver.


Added to /etc/inittab (comment out existing, and add this below. Replace username with your new user): 

1:2345:respawn:/bin/login -f USERNAME tty1 </dev/tty1 >/dev/tty1 2>&1

Copy /etc/profile to user that will be auto logging in: 

cp /etc/profile /home/USERNAME/.bash_profile

Appended to /home/USERNAME/.bash_profile : 

exec startx

When startx loads, it will pull settings from ~/.xinitrc for USERNAME so edit that (note that .xinitrc requires & after all commands that are not the final wm). 

#!/bin/bash
/usr/local/bin/surf "localhost/zm/cgi-bin/nph-zms??mode=jpeg&monitor=1&scale=100&maxfps=5&buffer=1000&user=user&pass=pass" &
exec dwm


Add an additional user beside the one used for the auto login, otherwise ssh will fail. ssh will try to startx when it loads, and it won't be able to. Add USERNAME2 permissions to sudoers. 

# adduser USERNAME2
nano /etc/sudoers


Disable screensaver for the first USERNAME per Arch Wiki: Display Power Management SIgnaling 

nano /home/USERNAME/.xinitrc

export DISPLAY=:0 &
xset s off &
xset -dpms &

These go before the other commands in .xinitrc, as they have the & symbol. The total .xinitrc will be something like: 

#!/bin/bash
export DISPLAY=:0 &
xset s off &
xset -dpms &
/usr/local/bin/surf "localhost/zm/cgi-bin/nph-zms??mode=jpeg&monitor=1&scale=100&maxfps=5&buffer=1000&user=user&pass=pass" &
exec dwm

Note: When troubleshooting xset. You must be the same user that is running X (ssh in as different user, then su to user). And, you must export DISPLAY to :0 or similar. Finally xset q should query the current settings.

Fine Tuning

At this point, you should be able to boot the SBC or desktop and receive a video feed without user interaction. However there are two problems (Beagle). One, it is not full screen. Two, video may be flickering.

Flickering Video

This is a known issue with Beaglebone. The simple solution is: install devmem2 or some other memory editing program, change an address. For details of why this is occuring see: [1] and [2] or search online.

Steps: 

git clone https://github.com/VCTLabs/devmem2
cd devmem2
make
make install

Append the memory adjustment to rc.local 

nano /etc/rc.local
devmem2 0x4c000054 w 0x00FFFFF10

Watch syslog and FIFO errors should immediately stop upon entering write command on memory.

Install steps source: Scivision: Devmem2 on the beaglebone black The author of devmem2 (Jan-Derk Bakker, website and code found at lartmaker.nl), his website is down at the moment. You can view the root domain at internet archive, but the page for devmem2 is not available. Others like VCTLabs above have copied his code to various spots. See also the Notes section below.

Full Screen Video Feed

Two options come to mind:

  • Point browser to a local html page with the link to the monitor embedded in an img tag

OR

  • have a local web server run and point surf to a hosted html page.

First Is easiest. Make an html file. Be sure to include http prefix. 

<html>
<img width="###px" height=###px" src="http://serverip/zm/cgi-bin/nph-zms?mode=jpeg&monitor=####&scale=100&maxfps=5&user=username&pass=password" />
</html>

Call it on .xinitrc before dwm 

surf file:///home/username/file.html &

Customize the width and height of the img tag to fit your monitor. In my case I put st in the .xinitrc of my beagle instead of surf, restarted, and from the terminal ran xrandr to see what display it was using. I had 1440x900 but the width and height I could get out of surf without borders causing trouble was 1415 and 875. Multiple img tags can be embedded into an html file however you like. See also Example Camera View HTML

Refresh Screen Periodically

You will want to have the web browser refresh every few minutes. Otherwise, if the feed drops out, it will not return unless you reboot. The way I accomplished this was:

Install xdotool 

# apt-get install xdotool

Edit surf config.h and add the following to the keybindings section, then make and make install. 

{ 0, GDK_F5,  reload, { .b = FALSE } },

Add to /etc/crontab 

DISPLAY=:0
*/5 * * * * username /usr/bin/xdotool key F5

To make sure this works, with the browser watching a camera stream, restart apache2 on the ZM server, and the browser feed will freeze. A successful F5 from xdotool will refresh the screen, as long as surf has a keybinding for it.

Accessing headless X via VNC

In the case that you have a headless device (no monitor attached) yet X is running, here's some tips for accessing the desktop via VNC. 

sudo apt-get install xserver-xorg-legacy
add:
allowed-users:anybody 
in /etc/X11/Xwrapper.config
apt-get install x11vnc

Final command may be something like 

ssh -L 5900:localhost:5900 user@pineboard  x11vnc -safer  -localhost -nopw -once -auth /tmp/serverauth*   -display :0

If you are doing headless on vnc, get rid of startx on bash profile and just run it manually.

Test x11vnc with 

x11vnc -display :0

But none of the other flags to start. When in doubt, break the commands down to make troubleshooting easier.

Todo

  • Make a guide similar to the above, but using stali, sabotage, or a similar static binary distro (would be faster / leaner).
  • This link here [3] goes a step further into optimizing video processing for the beaglebone black. While the kernel is probably already optimized for bbb hardware, there is room on the software side to compile for optimizations.
  • Also, consider the RPi and its Hardware encoding capabilities, roughly documented here in the forums.

Notes / Errata

  • The above install requires about 2GB (make partition 3GB or 4GB to be safe). dd or clonezilla the partition to an img to reuse later.
  • When troubleshooting any dropouts from watching the video feed, make sure to downscale the video, per Example_Camera_View_HTML for clients.

Troubleshooting

Installing and updating is slow!

On an SBC a counterfeit SD card could be the cause. A counterfeit or non name brand SD may take one day, what takes 2 hours to do with a name brand card.

Video monitor flickers, syslog says FIFO underflow!

See install steps regarding adjusting memory addresses with devmem2.

How do I disable keypresses for kiosk mode?

I don't have the need, but it's possible to do further lockdown. Look online.

Video is still flickering after devmem2 changes!

See my note. More research is needed. I was able to see the BBB running a ~3FPS 720p stream without error at one point, but at a later point, it began to drop out occasionally. It may be best to either run the viewing feed at a lower resolution, or to use a more powerful ARM based board (or a desktop if you don't need low power).

See Also

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