lazycast: A Simple Wireless Display Receiver
lazycast is a simple wifi display receiver. It was originally targeted Raspberry Pi (as display) and Windows 8.1/10 (as source), but it might also work on other Linux platforms and Miracast sources. (For other Linux systems, skip the preparation section. For video playback from Android sources, modify the player_select option in d2.py.) For Windows 10 systems, the Miracast over Infrastructure (MICE) feature is also supported, which may provide better user experiences. In general, lazycast does not require re-compilation of wpa_supplicant to support various p2p functionalities, and should work on an "out of the box" Raspberry Pi.
The wpa_supplicant installed on the latest Raspbian distribution does not seem to work properly. (See this.) For Raspbian Buster, try downgrading the wpasupplicant package to the version for Raspbian Stretch. Here is one solution:
wget http://ftp.us.debian.org/debian/pool/main/w/wpa/wpasupplicant_2.4-1+deb9u6_armhf.deb
sudo apt --allow-downgrades install ./wpasupplicant_2.4-1+deb9u6_armhf.deb
It is highly recommended to replace the "Wireless & Wired Network" in Raspbian with NetworkManager, which can maintain much more stable p2p connection.
Note that installing NetworkManager will reset the network and cause Pi to be disconnected from existing network. Therefore, these steps should be done locally and not over SSH. After the installation, you can connect to the network once again using the NetworkManager interface.
Here is one solution (adopted from here):
sudo apt install network-manager network-manager-gnome openvpn openvpn-systemd-resolved network-manager-openvpn network-manager-openvpn-gnome
And,
sudo apt purge dhcpcd5
Additionally, systemd-resolved should be disabled since it does not seem to work well with NetworkManager, which causes DNS problems. (See here for details.) (It may take a while for the problems to show).
sudo systemctl disable systemd-resolved
Then reboot:
sudo reboot
Install packages used to compile the players:
sudo apt install libx11-dev libasound2-dev libavformat-dev libavcodec-dev
Compile libraries on Pi:
cd /opt/vc/src/hello_pi/libs/ilclient/
make
cd /opt/vc/src/hello_pi/hello_video
make
Clone this repo (to a desired directory):
cd ~/
git clone https://github.com/homeworkc/lazycast
Go to the lazycast directory and then make:
cd lazycast
make
Run ./all.sh to initiate lazycast receiver. Wait until the "The display is ready" message. The name of the display will appear after this message. Then, search for this name on the source device you want to cast. The default PIN number is 31415926. If backchannel control is supported by the source, keyboard and mouse input on Pi are redirected to the source as remote controls.
It is recommended to initiate the termination of the receiver on the source side. These user controls are often near the pairing controls on the source device. You can utilize the backchannel feature to remotely control the source device in order to close lazycast.
Set the resolution on the source side. lazycast advertises all possible resolutions regardless of the current rendering resolution. Therefore, you may want to change the resolution (on the source) to match the actual resolution of the display connecting to Pi.
Modify parameters in the "settings" section in d2.py to change the sound output port (hdmi/3.5mm) and preferred player.
The maximum resolutions supported are 1920x1080p60 and 1920x1200p30. The GPU on Pi may struggle to handle 1920x1080p60, which results in high latency. In this case, reduce the FPS to 1920x1080p50.
To change the default PIN number, replace the string 31415926 in all.sh to another 8-digit number.
After Pi connects to the source, it has an IP address of 192.168.173.1 and this connection can be reused for other purposes like SSH. On the other hand, since they are under the same subnet, precautions should be taken to prevent unauthorized access to Pi by anyone who knows the PIN number.
Two in-house players are written for Raspberry Pi 3. VLC, omxplayer or gstreamer can be used instead on other platforms. (See here for details of installing gstreamer.)
lazycast tries to remember the pairing credentials so that entering the PIN is only needed once for each device. However, this feature does not seem to work properly all the time with recent Raspbian images. (Using the latest Raspbian is still recommended from the security perspective. However, recent Raspbians randomize the MAC address of the p2p-dev-wlan0 interface upon reboot, while old Raspbians (example) do not. Any insights or suggestions on this issue are appreciated, and could make this important feature work again.) Therefore, re-pairing may be needed after every Raspberry Pi reboot. Try clearing the 'lazycast' information on the source device before re-pairing if you run into pairing problems.
Player2 seems to have a double-free bug which causes it to crash when playing some videos. Currently a workaround (that constantly monitors the liveliness of player2) is implemented.
Latency: Limited by the implementation of the rtp player used. (In VLC, latency can be reduced from 1200 to 300ms by lowering the network cache value.)
Due to the overcrowded nature of the wifi spectrum and the use of unreliable rtp transmission, you may experience some video glitching/audio stuttering. The in-house players employ several mechanisms to conceal transmission error, but it may still be noticeable in challenging wireless environments. Interference from other devices may cause disconnections.
Devices may not fully support backchannel control and some keystrokes/clicks will behave differently in this case. The left Windows key is not captured and when it is pressed, it makes the current window to be out-of-focus and thus disables the backchannel controls. If it is pressed again the window will be in-focus.
HDCP(content protection): Neither the key nor the hardware is available on Pi and therefore is not supported.
Append this line to /etc/xdg/lxsession/LXDE-pi/autostart:
@lxterminal -l --working-directory=<absolute path of lazycast> -e ./all.sh
For example, if lazycast is placed under ~/ (which corresponds to /home/pi/), append the following line to the file:
@lxterminal -l --working-directory=/home/pi/lazycast -e ./all.sh
For Windows 10 sources, Miracast over Infrastructure (MICE) is a feature that allows transmission of screen data over Ethernet or secure wifi networks. The spec of Miracast over Infrastructure (MICE) is available here. Compared to wifi p2p, it allows stabler connection and lower latency. Although MICE relies on Ethernet or secure wifi network almost entirely, in the device discovery phase, it still requires a wifi p2p device to broadcast beacon and probe response frames to the source. (However, it might be possible to use two Pis so that one of the two does not need to have wifi hardware or be physically close to the source. One Pi would be used to trasmit the beacon while the other (that runs ./project.py) is used to project. For such setting to work, the variable hostname in mice.py must be set to the hostname of the machine running project.py. In the future, it might be possible to emulate a wifi card by HW/SW on the source so that wifi p2p will not be necessary.)
Currently, this feature is tested to be working with a Windows 10 PC and a Pi (with manually assigned IPs) connected via Ethernet. More tests might be needed, especially for different DHCP, DNS and firewall configurations. Ports used include but are not limited to UDP 53 (DNS), UDP 5353 (mDNS), TCP 7236 and TCP 7250. Also, the encryption feature is not implemented yet so it should only be used over trusted networks and it should not be used for sensitive data. MICE works in ipv6 networks but currently only ipv4 is implemented.
Follow the steps in the previous preparation section. Note that installing NetworkManager is required for MICE.
Install avahi-utils:
sudo apt install avahi-utils
Make sure the Windows 10 PC is on the same network as the Pi. You can try pinging the Pi from the PC.
Make sure there is no p2p interface that has already been created and all.sh is not running. (You can disable all.sh to start on boot and then simply reboot.)
Run ./mice.py.
Use the "Connect" tab in Windows 10 and try to connect to the hostname of Pi (e.g., raspberrypi). Windows may try to connect using the traditional method first and therefore may ask for PIN. In that case, simply cancel the connecting process and try again. You can also try relaunching mice.py and see if it helps. Since no encryption is implemented at the moment, the prompt for PIN should not appear using MICE.
Windows 10 assigns the name of the display differently when using MICE. If the monitor connected to the Pi is successfully detected by the PC, the name of the display (e.g., raspberrypi) will be changed to the name of the monitor. If the detection fails, the name of the display will be changed to "Device". After disconnection, the name of the display will be changed back to the hostname of Pi (e.g., raspberrypi).
If you wish to run MICE and wifi p2p simultaneously, set the parameter concurrent to 1 in mice.py and only uses mice.py. When there are multiple IPs assigned to the Pi and mDNS does not seem to be working, manually set the ipstr variable in mice.py to the target IP of Pi and a PC will try to connect to this IP directly.
Some parts of the video player1 are modified from the codes on https://github.com/Apress/raspberry-pi-gpu-audio-video-prog. Many thanks to the author of "Raspberry Pi GPU Audio Video Programming" and, by extension, authors of omxplayer.
Using any part of the codes in this project in commercial products is prohibited.