DIY DLAN screen projection solution under Linux

I used Python + FFmpeg + DLNA to complete a   screen projection solution under Linux . The disadvantage of this scheme is that the delay is a bit large.

Generally speaking, Android devices and Windows devices use the miracast protocol for screen projection, but this protocol requires the network card to support p2pwifi, and most network card drivers under Linux do not support p2pwifi.

So I used Python + FFmpeg + DLNA to complete a screen projection solution under Linux. The disadvantage of this scheme is that the delay is a bit large.

set up

Here's how to do it.

First install this DLNA library:

pip3 install dlna

Then use ​​pactl​​ to find “Monitor Source” (Chinese output) or “Monitor Source” (English output):

pactl list sinks

Sample output:

Sink #0
  State: RUNNING
  Name: alsa_output.pci-0000_05_00.6.HiFi__hw_Generic_1__sink
  Description: Family 17h (Models 10h-1fh) HD Audio Controller Speaker + Headphones
  Driver: module-alsa-card.c
  Sample Specification: s16le 2ch 44100Hz
  Channel Map: front-left,front-right
  Owner Module: 9
  Mute: no
  Volume: front-left: 53814 /  82% / -5.14 dB,   front-right: 53814 /  82% / -5.14 dB
          balance 0.00
  Base Volume: 65536 / 100% / 0.00 dB
  Monitor Source: alsa_output.pci-0000_05_00.6.HiFi__hw_Generic_1__sink.monitor
  Latency: 16676 usec, configured 16000 us...

Then create a CGI  script  ​​screen.flv​​. first. Create the directory where the script will be placed:

mkdir screencast
mkdir screencast/cgi-bin

Then create the script directly by ​​cat​​:

cat <screencast/cgi-bin/screen.flv
#!/bin/bash
echo "Content-Type:video/x-flv"
echo

ffmpeg -f pulse -i <监视器信源>   -f x11grab -i :0  -vcodec h264_nvenc  pipe:.flv
eof

Please replace ​​<monitor source>​​ in the file with the monitor source obtained above.

and set executable permissions for it:

chmod +x screencast/cgi-bin/screen.flv 

Note: If you don't have an Nvidia graphics card, or want to use other hardware acceleration, please replace the encoding scheme​​h264_nvenc​​ with the corresponding encoding scheme. Soft solution is not recommended because the delay is very high.

screencast

When you need to cast the screen, first start the local web server:

cd screencast
python3 -m http.server --cgi 9999&

Then, find your DLNA device and copy the URL after ​​location​​:

dlna device

Sample output:

=> Device 1:
{
    "location": "http://192.168.3.118:1528/",
    "host": "192.168.3.118",
    "friendly_name": "Kodi",
...

Find the LAN IP address of your Linux computer:

ip addr

Sample output:

3: wlp2s0:  mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 74:4c:a1:82:2e:3f brd ff:ff:ff:ff:ff:ff
    inet 192.168.3.117/24 brd 192.168.3.255 scope global dynamic noprefixroute wlp2s0
       valid_lft 58283sec preferred_lft 58283sec
    inet6 240e:3b3:2ee3:9530:d005:e492:6243:9/128 scope global dynamic noprefixroute 
       valid_lft 6738sec preferred_lft 3138sec
    inet6 240e:3b3:2ee3:9539:f289:6043:c56a:4e7b/64 scope global dynamic noprefixroute 
       valid_lft 7189sec preferred_lft 3589sec
    inet6 240e:3b3:2ee3:9539:3714:eaf0:c549:b8c9/64 scope global dynamic mngtmpaddr noprefixroute 
       valid_lft 7188sec preferred_lft 3588sec
    inet6 fe80::c746:2540:ab7b:20aa/64 scope link 
       valid_lft forever preferred_lft forever
    inet6 fe80::3543:2637:e0fc:3630/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

The command to start screencasting is as follows:

dlna play -d  http://<局域网 IP>:9999/cgi-bin/screen.flv

Please replace the ​​​​​ and ​​<LAN IP>​​ parameters accordingly. The command I replaced here is:

dlna play -d http://192.168.3.118:1528/ http://192.168.3.117:9999/cgi-bin/screen.flv

Then set up your TV to accept screencasting. Different TV devices have different screencasting methods. Please refer to the specific device instructions.

After a few moments, the video will appear on the TV. The screen projection effect is as follows:

About the Author:

calvinlin: An ordinary Shenzhen junior high school student.