Basically streaming videos does not change anything compared to streaming audio: you just have to use video files instead of sound files! For instance, if you want to stream a single file to an icecast server in ogg format (with theora and vorbis as codecs for audio and video) you can simply type:
source = single("video.mp4") output.icecast( %ffmpeg(format="ogg", %audio(codec="libvorbis"), %video(codec="libtheora") ),host="localhost", port=8000, password="hackme", mount="/videostream", source)
And of course you could have used a
playlist instead of
single to have multiple files, or used other formats for the stream.
In order to test a video stream, it is often convenient to use the
output.sdl operator (or
output.graphics) which will open a window and display the video stream inside. These can handle streams with video only, you can use the
drop_audio operator to remove the sound part of a stream if needed.
You should be expecting much higher resource needs (in cpu time in particular) for video than for audio. So, be prepared to hear the fan of your computer! The size of videos have a great impact on computations; if your machine cannot handle a stream (i.e. it’s always catching up) you can try to encode to smaller videos for a start.
Encoding with FFmpeg
%ffmpeg encoder is the recommended encoder when working with video. Not only does it support a wide range of audio and video formats but it can also send and receive data to many different places, using
output.url. On top of that, it also supports all the FFmpeg filters and passing encoded data, if your script does not need re-encoding.
The syntax for the encoder is detailed in the encoders page. Here are some examples:
# AC3 audio and H264 video encapsulated in a MPEG-TS bitstream %ffmpeg(format="mpegts", %audio(codec="ac3",channel_coupling=0), %video(codec="libx264",b="2600k", "x264-params"="scenecut=0:open_gop=0:min-keyint=150:keyint=150", preset="ultrafast")) # AAC audio and H264 video encapsulated in a mp4 file (to use with # `output.file` only, mp4 container cannot be streamed! %ffmpeg(format="mp4", %audio(codec="aac"), %video(codec="libx264",b="2600k")) # Ogg opus and theora encappsulated in an ogg bitstream %ffmpeg(format="ogg", %audio(codec="libopus"), %video(codec="libtheora")) # Ogg opus and VP8 video encapsulated in a webm bitstream %ffmpeg(format="webm", %audio(codec="libopus"), %video(codec="libvpx"))
Streaming with FFmpeg
The main input to take advantage of FFmpeg is
input.ffmpeg. It should be able to decode pretty much any url and file that the
ffmpeg command-line can take as input. This is, in particular, how
input.rtmp is defined.
For outputing, one can use the regular outputs but some of them have special features when used with
output.file is able to properly close a file after it is done encoding it. This makes it possible to encode in formats that need a proper header after encoding is done, such as
output.url will only work with the
%ffmpeg encoder. It delegates data output to FFmpeg and can support any url that the
ffmpeg command-line supports. *
output.harbor.hls should only be used with
%ffmpeg. The other encoders do work but
%ffmpeg is the only encoder able to generate valid
MP4 data segments for the HLS specifications.
Useful tips & tricks
Video is a really exciting world where there are lots of cool stuff to do.
Transitions at the beginning or at the end of video can be achieved using
video.fade.out. For instance, fading at the beginning of videos is done by
source = video.fade.in(transition="fade",duration=3.,source)
Adding a logo
You can add a logo (any image) using the
video.add_image operator, as follows:
source = video.add_image( width=30,height=30, x=10,y=10, file="logo.jpg", source)
Inputting from a webcam
If your computer has a webcam, it can be used as a source thanks to the
input.v4l2 operator. For instance:
Video in video
Suppose that you have two video sources
source2 and you want to display a small copy of
source2 on top of
source. This can be achieved by
source2 = video.scale(scale=0.2,x=10,y=10,source2) source = add([source,source2])
Adding scrolling text at the bottom of your video is as easy as
source = video.add_text.sdl( font="/usr/share/fonts/truetype/ttf-dejavu/DejaVuSans.ttf", "Hello world!", source)
You might need to change the
font parameter so that it matches a font file present on your system.
There are many of effects that you can use to add some fun to your videos:
video.lomo, etc. Read the documentation to find out about them. If you have compiled Liquidsoap with frei0r support, and have installed frei0r plugins, they will be named
video.frei0r.*. You can have a list of those supported on your installation as usual, using
Presenting weather forecast
You can say that a specific color should be transparent using
video.transparent. For instance, you can put yourself in front of a blue screen (whose RGB color should be around 0x0000ff) and replace the blue screen by an image of the weather using
img = single("weather.jpg") cam = input.v4l2() cam = video.transparent(color=0x0000ff,precision=0.2,cam) source = add([img,cam])
Let’s design an ``anonymizer’’ effect: I want to blur my face and change my voice so that nobody will recognise me in the street after seeing the youtube video. Here is what we are going to achieve:
This video was produced thanks to the following script:
# Input from webcam cam = input.v4l2() # Detect faces (this generates a white disk over faces) mask = video.frei0r.opencvfacedetect(cam) # Pixellize the video censored = video.frei0r.pixeliz0r(blocksizex=0.1,blocksizey=0.1,cam) # Generate a mask for video without the face unmask = video.frei0r.invert0r(mask) # Put the pixellized face over the video s = video.frei0r.addition( video.frei0r.multiply(mask,censored), video.frei0r.multiply(unmask,cam)) # We have to bufferize the source because its clock it GStreamer's clock s = buffer(buffer=0.1,mksafe(s)) # Input audio from microphone mic = input.pulseaudio(clock_safe=false) # Transpose sound to generate a funny voice mic = soundtouch(pitch=1.5,mic) # Add sound to video s = mux_audio(audio=mic,s) # Let's hear the sound output.pulseaudio(fallible=true,s) # Let's see the video output.sdl(fallible=true,drop_audio(s)) s = mksafe(s) # Output the video/sound into a file in theora/vorbis format output.file(%ogg(%theora(quality=63),%vorbis), "anonymous.ogv", s)
Controlling with OSC
In this example we are going to use OSC integration in order to modify the parameters in realtime. There are many OSC clients around, for instance I used TouchOSC :
Here is how the video was made:
# Set the OSC port to match TouchOSC's default port settings.osc.port.set(8000) # Input from the webcam s = input.v4l2_with_audio() s = mksafe(s) # We get the angle from fader 3 angle = osc.float("/1/fader3", 0.) # we rescale the position of fader 3 so that it corresponds to a 2π rotation angle = fun() -> angle() * 3.1416 * 2. # ...and we rotate the video according to the angle s = video.rotate(speed=0.,angle=angle,s) # Change brightness according to fader 1 s = video.frei0r.brightness(brightness=osc.float("/1/fader1",0.5),s) # Change contrast according to fader 2 s = video.frei0r.contrast0r(contrast=osc.float("/1/fader2",0.5),s) # We have to buffer here otherwise we get clocks problems s = buffer(s) # Output sound and video output.pulseaudio(fallible=true,s) output.sdl(fallible=true,drop_audio(s))
You want to show yourself in front of a video of a bunny, as in
The idea is to film yourself in front of a blue screen, make this blue screen transparent and put the resulting video in front of the bunny video (actually, I don’t have a blue screen at home, only a white wall but it still kinda works).
# The video of the bunny s = single("big_buck_bunny_720p_stereo.ogg") # Input from the webcam cam = input.v4l2() # Flip the video around a vertical axis so that it is easier # to position yourself cam = video.frei0r.flippo(x_axis=true,cam) # Make the white background transparent # I had to tweak the precision parameter so that I will be seen # but not the wall cam = video.transparent(color=0xffffff,precision=0.64,cam) # Superpose the two videos s = add([s,cam]) # Output to SDL output.sdl(fallible=true,drop_audio(s))