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Last modified: Sun, 22 Feb 2015
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Live streaming

Container
Codecs
Streaming services
- twitch.tv
- livestream.com
UDP streaming
Streaming with ffserver/avserver
RTMP streaming with nginx + RTMP module

Since SimpleScreenRecorder uses ffmpeg/libav libraries to handle the encoding and formatting, it can also make use of ffmpeg/libav's ability to do live streaming. Live streaming is not my highest priority, but if you're interested in streaming and you need some specific feature, feel free to contact me.

You will need a pretty powerful computer to do live streaming. When you're just recording a video, the codecs are configured for high performance, which will increase the bitrate but reduce the CPU load. But when you're doing live streaming, the bitrate should be as small as possible, so this can't be done. So unless you have a really powerful processor, you shouldn't try to record at high resolutions.

Hint

Unfortunately, the streaming support in ffmpeg/libav isn't nearly as robust as the rest of ffmpeg/libav. RTMP streaming (explained below) appears to be reliable, but many other protocols and containers are not. Don't be surprised if SimpleScreenRecorder closes or freezes without any explanation. Some useful hints:

Run SimpleScreenRecorder from a terminal, so you can see error messages produced by ffmpeg/libav or other libraries. These won't show up in the log in SimpleScreenRecorder.
Make sure you have a reliable internet connection. Avoid wireless if possible.
If you can't connect, check your firewall (for RTMP, ffmpeg/libav may kill the process without any error message if the connection is refused).
If possible, try to get the latest version of ffmpeg/libav (ffmpeg is preferred if you have a choice).

Container

Not all containers are suitable for streaming. Some containers (e.g. MP4) put important metadata at the end of the file, so if you try to stream those files, you won't see anything. Containers that are known to work are 'flv' and 'mpegts' (found under 'Other'). Matroska also appears to work, but not all players support it.

Note

In many cases, it takes some time before a stream starts playing, because the player has to wait for a keyframe. During this period you may even get error messages (e.g. complaining about missing frames). Wait at least 30 seconds before concluding that it doesn't work.
Some media players (VLC, ffplay) appear to be unable to play flv streams that have no audio.

Codecs

The codecs you can use are limited by the container that you're using. The most common codecs are H.264 for video and AAC for audio (this works for flv and mpegts).

If you're using H.264, SimpleScreenRecorder will by default use 'constant quality mode'. This means the bitrate will vary depending on the complexity of the video. This is great for normal recording, where you only care about the total file size, but not so much for live streaming. You can get around this by setting the codec to 'Other', and then choosing 'libx264'. This is the same codec, but now it will be used with a fixed bitrate, which is better suited for streaming.

Streaming services

You can stream to websites like twitch.tv and livestream.com if you know the RTMP URL.

Set the container to 'flv'.
Put the RTMP URL in the 'save as' field in SimpleScreenRecorder.
Uncheck 'separate file per segment'
Set the video codec to libx264 (not H.264, that one won't allow you to change the bit rate).
Set the bit rate to a reasonable value, for example 2000 kbps. The value should be significantly lower than the upload speed of your internet connection, otherwise it will not work well.
In the custom video codec options field, enter preset=faster,minrate=2000,maxrate=2000,bufsize=2000,keyint=60. The value of 'minrate', 'maxrate' and 'bufsize' should be equal to the bit rate. For more information about custom codec options, read this.
Set the audio codec to AAC.

twitch.tv

You can get a list of RTMP servers here (based on this). Pick one that's near you.

After picking a server, you should go your Twitch dashboard, log in, and click 'stream key'. Now click 'show key' to see your stream key. You then have to append this to the RTMP URL. Example:

rtmp://live-ams.twitch.tv/app/live_AgPUV1rXJnKm4Qg8

livestream.com

I haven't tested this, but this forum thread says that it's possible. The URL is:

rtmp://publish.livestream.com/mogulus/YOURCHANNELNAME/username=YOURUSERNAME/password=YOURPASSWORD/isAutoLive=true

The bandwidth is limited to 500kbps though (that's video and audio combined).

UDP streaming

This is probably the simplest way to do streaming, but it also has some serious downsides. UDP is an unreliable transport system: packets can go lost and this will lead to corrupted video. This is not a problem when you're streaming over your LAN where packet loss is extremely unlikely, but if you stream over the internet, or even over a wireless connection, you will probably lose some packets.

Since UDP is point-to-point, you can only play the stream on one computer, and you need to know the IP of that computer.

You can do UDP streaming by entering udp://ipaddress:port in the 'save as' field in SimpleScreenRecorder.

You can then receive this stream in a video player like VLC or MPlayer. In VLC you would do this by clicking Media > Open Network Stream and entering udp://@:port. With some containers (e.g. flv), you should start the player before you start streaming to receive anything at all, while with other containers (e.g. mpegts) you can start the player whenever you want.

Streaming with ffserver/avserver

There's a utility called ffserver/avserver that can act as a streaming server for ffmpeg/libav. Theoretically it should be possible to make this work with SimpleScreenRecorder, but I haven't figured out how. The program is a bit weird, instead of just re-streaming whatever ffmpeg/libav sends to it, it actually tells ffmpeg/libav what format and codec it should use, and I have no idea how SimpleScreenRecorder is supposed to react to that.

It doesn't really matter though, because the next method works perfectly.

RTMP streaming with nginx + RTMP module

This takes more time to set up, and it's not particularly easy, but I think it's worth it. You will need:

The nginx source code
The nginx RTMP module source code
Optionally, a flash player to embed the stream in a webpage, like Flowplayer. You can also use a media player like VLC, but it's easier to point people to a webpage.

I don't particularly like flash, but there really are no good alternatives at this point (HLS comes close, but apparently the latency is a lot higher, and not all browsers support the same codecs).

The nice thing about RTMP is that the same protocol can be used not just to play a stream, but also to supply it. This means SimpleScreenRecorder can simply stream to rtmp://localhost:10200/live/nameofstream (just put that URL in the 'save as' field), and other clients will then be able to play that same URL. SimpleScreenRecorder doesn't need to act as a server and isn't exposed to the internet.

First you should set up the RTMP server. You have to compile nginx together with the RTMP module, instructions can be found at the github page for the RTMP module. Then you need to configure the server by modifying the nginx configuration file. All options are explained on the nginx and RTMP module websites. Here's the configuration that I used:

worker_processes 1;

events {
    worker_connections 100;
}

http {
    include mime.types;
    default_type application/octet-stream;
    server {
        
        listen 10201;
        
        location /live/ {
            try_files /live/live.html =404;
        }
        location = /stats {
            allow 127.0.0.1;
            deny all;
            rtmp_stat all;
            rtmp_stat_stylesheet stat.xsl;
        }
        
    }
}

rtmp {
    server {
        
        listen 10200;
        
        wait_key on;
        wait_video on;
        
        application live {
            
            live on;
            
            allow publish 127.0.0.1;
            deny publish all;
            
            allow play all;
            
        }
        
    }
}

This tells nginx to run an RTMP server on port 10200 and an HTTP server on port 10201. The HTTP server hosts an HTML page (/live/live.htm) and the flash player (Flowplayer). Here's a simple example of what the HTML page could look like:

<html>

<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<script type="text/javascript" src="../flowplayer-3.2.12.min.js"></script>
<title>Live video stream</title>
</head>

<body>

<h1>Live video stream</h1>

<div id="player" style="width:854px;height:480px"></div>

<p id="streaminfo"></p>

<script type="text/javascript">

m = location.href.match(/^http:\/\/([a-zA-Z0-9._-]+):[0-9]+\/live\/(.*)$/);
host = m[1];
name = m[2];

document.getElementById("streaminfo").innerHTML = "Streaming: <b>rtmp://" + host + ":10200/live/" + name + "</b>";

flowplayer("player", "../flowplayer-3.2.16.swf", {
    clip: {
        url: name,
        live: true,
        scaling: "fit",
        provider: "rtmp"
    },
    plugins: {
        rtmp: {
            url: "flowplayer.rtmp-3.2.12.swf",
            netConnectionUrl: "rtmp://" + host + ":10200/live"
        }
    }
});

</script>

</body>

</html>

Nginx is set up so that every URL starting with /live/ gets redirected to that page, and then that page simply uses javascript to read the full URL and decide what stream should be played. If you go to http://localhost:10201/live/nameofstream, it will stream from rtmp://localhost:10200/live/nameofstream.

You can also get statistics by going to http://localhost:10201/stats (you should get the stat.xsl file from the RTMP module source code).

You can also use other streaming servers (e.g. Red5), I'm pretty sure that those will work too.

Comments

Dubslow

Comment #1: Mon, 9 Sep 2013, 7:37 (GMT+1, DST)

Maarten Baert's website

Navigation

Log in

Live streaming

Hint

Container

Note

Codecs

Streaming services

twitch.tv

livestream.com

UDP streaming

Streaming with ffserver/avserver

RTMP streaming with nginx + RTMP module

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