ffmpeg - is the default standard for video operations of all kind
If you just want to update some text on the screen the easiest method is to use the drawtext filter with the textfile and reload options.
ffmpeg -i input -vf "drawtext=textfile=songs.txt:reload=1" output songs.txt will be reloaded once per frame. Be sure to update it atomically, or it may be read partially, or even fail.
If you prefer an image instead of text you have to manually select the image demuxer, loop the image, and replace overlay.png atomically whenever you want it to be updated.
ffmpeg -i input -f image2 -loop 1 -i overlay.png -filter_complex overlay output
You can do this with v4l2loopback. First you need to install it:
sudo apt install v4l2loopback-dkms
sudo modprobe v4l2loopback
This is easy but older versions of v4l2loopback have some known bugs, so consider compiling it instead if you encounter any issues.
If it's not in the repository for your Ubuntu version, or you want the latest version, you can compile it:
sudo apt-get install build-essential checkinstall
wget https://github.com/umlaeute/v4l2loopback/archive/master.zip
unzip master.zip
cd v4l2loopback-master
make
sudo checkinstall --pkgname=v4l2loopback --pkgversion="$(date +%Y%m%d%H%M)-git" --default
sudo modprobe v4l2loopback
If you want to remove the package you compiled:
sudo apt-get remove v4l2loopback
Note that the actual video number may vary depending if an existing device is already using /dev/video0. Check output of ls /dev/video* or v4l2-ctl --list-devices.
Now run ffmpeg. Example for desktop using x11grab:
ffmpeg -f x11grab -framerate 15 -video_size 1280x720 -i :0.0 -f v4l2 /dev/video0
ffmpeg -re -i input.mp4 -map 0:v -f v4l2 /dev/video0
ffmpeg -re -loop 1 -i input.jpg -vf format=yuv420p -f v4l2 /dev/video0
Such as if you want to do some filtering. This example will flip the image vertically.
ffmpeg -f v4l2 -i /dev/video0 -vf vflip -f v4l2 /dev/video1
If you get error Unknown V4L2 pixel format equivalent then add the output option -vf format=yuv420p.
ffplay /dev/video0
- Unable to open V4L2 device '/dev/video0'
- Failed to open /dev/video0: No such file or directory
- Unknown V4L2 pixel format equivalent for yuvj422p
See this answer for solutions.
You can create a virtual desktop with Xvfb and stream that. To create a virtual X client and server:
$ Xvfb :100 -screen 0 800x600x24 & To open an X applications inside of the virtual client, set the $DISPLAY variable:
$ DISPLAY=:100 feh ~/pictures/stallman.jpg Now you can stream a video feed of the virtual X client to a server using ffmpeg and netcat:
$ ffmpeg -f x11grab -s 800x600 -r 30 -i :100 -an -q 10 -f mjpeg - | nc -lp 5000 And receive the video on another device on the LAN and play it back with ffplay:
$ nc 5000 | ffplay -
You can send keyboard events to the virtual X client with xdotool or xmacro. xmacro has a flag that allows it to receive stdin, as well as a recording tool that spits stdout. This can be combined with netcat to send key and mouse events.
$ xmacrorec | nc -lp 9002 and nc 192.168.100.100 9002 | xmacroplay :0
pavucontrol - gui client that can route audio
snd-aloop - is the kernel module for setting up virtual audio loopback devices.
$ sudo modprobe snd-aloop
creates two devices 0 & 1 under a new “Loopback” card for both playback & capturing, as shown below, respectively:
$ sudo aplay -l $ sudo arecord -l
Start recording audio from hw:2,1,4:
$ arecord -D hw:2,1,4 -f S16_LE -c 2 -r 48000 recorded.wav
Note that providing the sample format, channel count, frame rate in recording ensures that playback picks up the same settings – this is because there is no real hardware underneath it is just a virtual loopback connection.
And in parallel (from another shell) play an audio from audio.wav into hw:2,0,4:
$ aplay -D hw:2,0,4 audio.wav And you’d find that recorded audio contains the played one – a loopback in action. You may play the recorded audio as follows:
$ aplay recorded.wav This would play on your system’s default speaker.
Also, note that there may be problem in just playing any audio.wav file because of the mismatched audio format etc support. For that, just record a new wave file with your speech using the following command:
$ arecord -f S16_LE -c 2 -r 48000 audio.wav This would record from your system’s default mic.
Interestingly, audio loopback could also be achieved in user space using alsaloop from alsa-utils package. Here is a demo of the same. From the output of aplay -l, hw:1,0 is the analog out (speaker). Note that hw:1,0 is same as hw:1,0,0. Find the equivalent on your system. And, now let’s loopback the virtual audio capture device hw:2,1,4 to this:
alsaloop -C hw:2,1,4 -P hw:1,0 On another shell, do the earlier playing:
$ aplay -D hw:2,0,4 audio.wav
This time you should be able to hear the audio.wav directly through system’s default speaker – again a loopback in action – rather two loopbacks in action: audio.wav -> hw:2,0,4 -> (loopback through snd-aloop driver) -> hw:2,1,4 -> (loopback through alsaloop app) -> hw:1,0 -> heard on speaker.
https://askubuntu.com/questions/453109/add-fake-display-when-no-monitor-is-plugged-ingist
exporting a obs source to diffrent devices.