Streaming video with VLC
Occasionally one wants to stream video for various reasons, whether it’s within the institutional network or a live feed from a conference venue. A few years ago Greg Tourte and I wrote a paper about the process of streaming video from a DV camera using FireWire, encoding into Ogg Theora/Vorbis, and transmitting the result to an audience via IceCast. For no adequately explored reason I have found myself playing with VLC’s inbuilt streaming methods for various purposes over the last week or so, and since VLC isn’t especially well documented, I’ve put the results up here.
1) Streaming video to an icecast server.
Once you have the icecast server set up this is actually shockingly easy to do. Set up a mountpoint on the server side, in your icecast.xml setup (/usr/local/etc/icecast.xml by default):
<mount>
<mount-name>/test.ogg</mount-name>
<username>myusername</username>
<password>mypassword</password>
<max-listeners>10</max-listeners>
<burst-size>65536</burst-size>
</mount>
for example.
Now, on the client side (which could be anything from Windows to Linux to MacOS, because VLC is cross-platform, but this example is Windows), try
C:\Users\Em>”c:\Program Files (x86)\VideoLAN\VLC\vlc.exe” “C:\Users\Public\Videos\My Video.wmv” –sout=#transcode{vcodec=theo,vb=800,scale=1,acodec=vorb,ab=128,channels=2,samplerate=44100}: std{access=shout,mux=ogg,dst=myusername:mypassword@myicecastserver.domain.com:port/test.ogg}
It should transcode on the fly into Ogg Vorbis/Theora and throw it at your icecast server. Viewers who go to myicecastserver.domain.com:port should be able to view it from there. Note that you can change various settings on the transcode process (for example scale=0.5, vb=400), so you can reduce the network bandwidth required, for example, but that paradoxically reducing some of these settings will actually increase the time taken for the transcoding process, so it can result in the transcode getting laggier than it was already.
Why transcode? Well, icecast only handles a limited format set. It’s really designed for audio data, not audiovisual. It’ll handle pretty well anything in an Ogg wrapper, though, and it is free. So if you want to stream video with Icecast, transcoding will probably be involved somewhere.
2) Streaming from a DVD (previously recorded event)
One would expect this to be as simple as
“c:\Program Files (x86)\VideoLAN\VLC\vlc.exe” dvdsimple:///E:/#1
but as it happens this seldom works, and the reason is the reaction time. Icecast is contacted with a header as soon as the streaming process begins. If it takes too long to get the DVD spun up and begin the process of streaming, icecast simply times out on you, leaving an error message along the lines of ‘ WARN source/get_next_buffer Disconnecting source due to socket timeout’.
Having tested this on various platforms, I find that the following string: “vlc dvdsimple:///dev/dvd –sout=’#transcode{vcodec=theo,vb=200,scale=0.4,theora-quality=10,fps=12,acodec=vorb,ab=48,channels=2}:std{access=shout,mux=ogg,dst=username:password@myicecastserver.domain.com:port/destination.ogg}’ –sout-transcode-audio-sync –sout-transcode-deinterlace” works very well in some cases. Apparently the DVD drive I first tested this with is just unusually slow. This DVD, being homegrown, doesn’t require libdvdcss to view/transcode.
3) Streaming with ffmpeg2theora
Bit of a Linux solution, this one. Install libvpx, libkate, scons and ffmpeg (all available as Slackbuilds for those who are that way inclined). Install ffmpeg2theora. Install libshout and oggfwd.
Then: try a command line along the lines of the following:
ffmpeg2theora /source/material/in/ffmpeg/readable/format.ext -F 16 -x 240 -c 1 -A 32 –speedlevel 2 -o /dev/stdout - | oggfwd myicecastserver.domain.com server_port password /test2.ogg
Obviously the output of this is not exactly high-quality; it’s been resized to a width of 240 pixels, audio has been reduced in quality, framerate’s been reduced to 16. But all these configuration options can be played with. Here’s a useful help page: http://commons.wikimedia.org/wiki/Help:Converting_video/ffmpeg2theora
Having called this a Linux solution, it’s worth pointing out that ffmpeg2theora is available for Windows (http://v2v.cc/~j/ffmpeg2theora/download.html) and that oggfwd/ezstream (http://www.icecast.org/ezstream.php/) have been used successfully on Windows as well. It’s also worth noting that, again, VLC can do the ogg/theora encoding too (and has done since 2006)- it’s just a question of seeing what’s better optimised for your purpose on your platform.
Note also that in this instance no username is needed, and the password used in this case is that set in the ‘<source-password>’ directive in icecast.xml.
4) Streaming without icecast
Icecast is a useful default solution if you want to broadcast your event/recording to multiple people across the web. It’s also useful because, operating via HTTP, it doesn’t suffer from the sort of firewall/router problems that UDP-based video streaming, for example, typically encounters. On the other hand, if you’re streaming across a local LAN (for example, into the next room), there’s (usually) no network border police to get in your way — and VLC does also offer a direct VLC-to-VLC HTTP-based streaming solution. Unlike Icecast, though, it’s not ideal for one-to-many broadcast.
The Videolan documentation has a graphical explanation of this setup: http://www.videolan.org/doc/streaming-howto/en/ch02.html
5) Mixing video for streaming
An obvious application to test in this context is FreeJ. Sadly it’s a bit of a pain to compile as it doesn’t seem to have been touched for a while. You’ll need to use the following approach for configuring the code:
CXXFLAGS=-D__STDC_CONSTANT_MACROS ./configure –enable-python –enable-perl –enable-java –disable-qt-ui
Typing ‘make’ will result in : error: ‘snprintf’ was not declared in this scope. Add #include <stdio.h> to any files afflicted in this way.
You then come across a crop of errors resulting from changes in recent ffmpeg. Some of these can be resolved with a patch, the rest, you’re better off going to the git repository rather than trying a stable version.
In principle you probably want to enable-qt-gui, but since it doesn’t currently compile I have left it as an exercise for some other day.
And once you have FreeJ working, you need to read the tutorial. Note this advice regarding addition of an audio track to FreeJ output.
