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Using a Raspberry Pi to Show a CCTV Stream

I wanted to be able to watch the live footage from security cameras at home on a TV. I learnt that the DVR the cameras connect to can stream the video feeds over the local network with a password-protected RTSP connection. I was able to set this up, eventually figure out the URLs, and view the streams on my PC using VLC media player.

Further research showed that this could be played using omxplayer on a Raspberry Pi, and that even the Raspberry Pi Zero should be able to show the video with its hardware video-decoding capabilities. I thought this was perfect because this model is very small, very low-powered, and very cheap. In addition, most TVs now have USB ports which can be used to power the Raspberry Pi, making the deployment straightforward.

Considering the Raspberry Pi Zero does not have any networking capability built-in, I decided to get the Raspberry Pi Zero W which has built-in Wi-Fi and Bluetooth, one micro-USB port to charge, one micro-USB OTG port, and one mini-HDMI port.

With this plan in mind, I purchased it with a mini-HDMI adapter and HDMI cable. Originally, I intended to set up the RPi entirely on my PC, meaning I would not need to buy an adapter to plug a keyboard into it. This didn’t quite work out for me… over many attempts… which lasted weeks on end…

However, I did manage to work out the issues eventually! This guide does the installation without connecting a keyboard or display to the RPi.

Be aware, the micro-USB ports are very close together. I was not able to fit a cheap micro-USB-to-USB adapter alongside the micro-USB charging cable. I literally had to file away the plastic on one side of the adapter.

In addition, my normal keyboard did not work with the Raspberry Pi Zero W. The LED lights lit up, but I could not type anything. A different wireless battery-powered keyboard worked fine, so the issue may have been related to powering the keyboard.

The tools for the job including the mutilated microUSB adapter.

Installing Arch Linux ARM

In order to do a remote install of the Raspberry Pi Zero W, we will need:

  • The RPi itself with USB power accessories, and
  • A microSD Card for the RPi with a microSD Card Reader for your PC.

Once installed, we should be able to SSH in to the RPi without ever having to connect a keyboard or monitor to it. (Of course, for this project we will connect the RPi to a display later anyway to show the video stream.)

The basic installation is the same: https://archlinuxarm.org/platforms/armv6/raspberry-pi.

On top of this, we will set up the Wi-Fi so that when we turn the RPi on for the first time it will automatically connect.

Configure the Wi-Fi network

Generate the configuration file with wpa_passphrase <YOUR SSID> >> /etc/wpa_supplicant/wpa_supplicant-wlan0.conf. The command will request the Wireless Password PSK, which I entered as “PLAIN PASSWORD” for the output below.

network={
    ssid="SSID"
    #psk="PLAIN PASSWORD"
    psk="PSK"
}

The #PSK= line can be removed.

Automate the Wi-Fi connection

Enable the wireless service:

$ ln -s /usr/lib/systemd/system/wpa_supplicant@.service /etc/systemd/system/multi-user.target.wants/wpa_supplicant@wlan0.service

We also need to enable a DHCP client to obtain an IP address for the RPi. We will use systemd’s built-in DHCP client to avoid needing to install another client.

Create /etc/systemd/network/25-wireless.network with

[Match]
Name=wlan0

[Network]
DHCP=ipv4

Fix the Raspberry Pi Zero W booting issue

In addition, the Raspberry Pi Zero W may not boot properly without a HDMI display plugged in. This caught me out for a very long time.

Edit /boot/config.txt with the following additional line

hdmi_force_hotplug=1

We are now done and can now turn on the RPi

Now, we can move the microSD card to the RPi, connect the power, give it a minute to boot up, and SSH in from our PC.

My PiServer book has a plethora of additional notes on how to connect to, configure, secure and increase the lifespan of an RPi and its microSD card.

Playing the Video Stream over the Network

For this part, we will need:

  • A mini-HDMI cable connected to a monitor.

The video surveillance system outputs an RTSP video stream over the network. Most applications like VLC, MPV, and ffplay can play these streams.

We will use omxplayer on the RPi because it just works. Unfortunately, I ran into issues with both MPV and ffplay when trying to output the video directly on to the framebuffer without the X11 window server running.

# pacman -S --needed omxplayer
$ omxplayer "rstp://user:pass@host:port/path/subpath" --avdict rtsp_transport:tcp --no-osd --live --with-info --stats

Description of parameters:

  • --avdict rtsp_transport:tcp was used because I experienced significant packet loss with the default UDP transport, which periodically caused the bottom half of the video to be overrun with artefacts.
  • --no-osd removes some annoying logging output on the terminal.
  • --live because this is a live stream - but I didn’t notice any difference…
  • --with-info outputs some stream information before the video starts playing.
  • --stats outputs ongoing information.

In addition, there is a --refresh parameter which will change the output resolution and frame rate to match the video (apparently, but I noticed no change). However, it is dangerous because if omxplayer does not exit gracefully (i.e. press q not <CTRL>-c), then the screen will just be black!

Having Everything Just Work Out-of-the-Box

We can configure systemd to automatically log a user in on boot.

First, create a restricted user:

$ useradd --create-home cctv
$ passwd --lock cctv

This will help protect the device despite automatically logging a user in.

Then, edit its .bashrc to immediately play the stream when the user logs in:

while true; do
    omxplayer "rstp://user:pass@host:port/path/subpath" --avdict rtsp_transport:tcp --no-osd --live --with-info --stats;
    sleep 1
done

This will also restart the video if there are any errors, for example if the internet connection is lost.

Finally, override the initial virtual console configuration to log the user in automatically when the device starts; systemctl edit getty@tty1:

[Service]
ExecStart=
ExecStart=-/sbin/agetty --autologin cctv --noclear %I $TERM

With this trio of changes, when power is connected to the RPi, the device will boot into Linux TTY1. This will immediately log the cctv user in without prompting for a password. Then, the user’s bash initialisation will automatically start the video stream which will output via HDMI.

We note that we can always switch to another TTY to login if we need to do maintenance using <CTRL> + <ALT> + <F2>.

Some Rough Edges

There are a few rough edges:

  • The Raspberry Pi Zero W running Arch Linux ARM takes just over 30 seconds to boot-up before the user is logged in. Plus there is an additional several seconds for the Wi-Fi to connect and the video to start playing. This means it feels like the device takes an eternity to play the video when it is powered on. This is annoying/problematic if the USB port on the TV disables the power output when the TV is off.
  • We will need to SSH in periodically to upgrade the system. Perhaps this could be automated?
  • Automatically logging a user in and use .bashrc to play the stream may not be the most secure method. There are alternatives using systemd.
  • Connecting to a new Wi-Fi network is a little painful, but it can be done by plugging in a keyboard, or pulling out the SD card to edit it on your PC.
  • The SD Card is not encrypted, leaving the Wi-Fi and RTSP stream credentials exposed, and the device vulnerable to attack. In addition, considering how small the device is, it could easily be stolen. However, I think these are insignificant issues considering the usage of the device.

Conclusion

Now we have a portable device requiring minimal maintenance that can be plugged in anywhere at home simply with HDMI and USB cables in order to view CCTV footage.

Bonus: Quickly Pulling up the Stream on your PC

We could create a keyboard shortcut to a script that pulls up the stream on our PC!

#!/usr/bin/sh

(cvlc --no-osd --fullscreen --key-quit q "rtsp://user:password@host:port/path/subpath" 2>/dev/null) &

Bonus: Connecting to Multiple Wi-Fi Networks

The Wi-Fi configuration shown earlier will connect to one specific Wi-Fi network automatically. We can list further networks in the same file, and even assign the order in which to try to connect to, e.g. priority=100.

We can auto-connect to any unsecure Wi-Fi network as a fallback with:

network={
   key_mgmt=NONE
   priority=-999
}