Streaming media with ffserver

Introduction

If you need to ​stream your audio/video content over the internet, you'll usually need a streaming (broadcasting) server, one of which is ​ffserver. It is able to collect multiple input sources (usually ffmpeg applications) and transcode/remux/broadcast each of them using multiple output streams. The simple diagram is shown on the image below:

Various input sources (ffmpeg applications) can be used to "feed" the broadcasting server (ffserver) with multimedia content that will be distributed to multiple clients for viewing. The purpose of the above image is to visually show the ability to separate parts of your streaming system into pieces that can be deployed around the world, allowing you to broadcast various live events without the need to change the structure of your streaming media system.

Let's take a closer look of ffserver, to better describe its possibilities. Consider the following image:

There are several elements shown on the image. Let's name them all first:

• Input sources (I)
• Feeds (F)
• Streams (S)
• Media players (P)

Input sources

These elements are not part of internal structure of ffserver tool, but rather represent external applications (usually ffmpeg), which can send audio/video streams to ffserver that will be distributed (broadcast) to all the viewers (media players). Since ffmpeg is mostly used as an input source, we'll describe it here in this document.

Input sources will connect to ffserver and bind themselves with one or more feeds if those feeds are not bound with some other input source at that moment. Binding one input source to multiple feeds is possible and makes sense only if the input source can produce different stream input for each feed it is bound to. It's useless for the input source to provide the same stream input to several feeds, since ffserver already has got a way of associating a single feed to multiple output streams.

Feeds

Feed element is an internal part of ffserver which has a purpose to associate one input source with one or more output streams. The possibility to associate a feed with more output streams is useful when you want to stream one input source (for example, your webcam with audio) using several different output formats (for example, streaming a full HD video and a small-size preview video for mobile phones) at the same time. Shortly speaking, each feed element logically represents each of your input sources. It can be considered as an "input jack" of ffserver, to which you connect your audio/video sources.

Streams

A stream element is internal part of ffserver and represents a connection point for all your viewers who wish to get a specific stream. For example, if you want to stream one full HD video and a small-size preview video for mobile phones, you will create one feed element (to connect your input to) and associate it with two stream elements (which will define different frame size, encoding type and/or output format). Each stream element can handle multiple connecting clients, just like one web server can handle multiple web clients. It can be considered as an "output jack" of ffserver, to which your viewers (media players) can connect to view your audio/video stream. The obvious difference between a feed element and a stream element (between input/output jack) is that a single stream element can handle multiple connections with viewers, while a single feed element is always connected to only one input source.

Media players

Media player elements are not internal part of ffserver. They just represent your viewers from the "outside world" that are connecting to the various stream elements to view your multimedia content. Some of the popular media players are: ​ffplay, ​VLC, ​Winamp, ​Windows Media Player, etc.

Running ffserver

To be able to successfully start ffserver, you'll need a valid ​configuration file first. Once you create a valid config file, you can start ffserver simply by running the following command:

ffserver -f /etc/ffserver.conf

Depending on your configuration file, your ffserver will start or not :) But more often it will not start until you debug all the issues that usually occur, including syntax errors, so you'll most probably want to run your ffserver in debug mode with "-d" option, until you sort out everything, like this:

ffserver -d -f /etc/ffserver.conf

You can always get a full list of options with:

ffserver --help

When you finally build a valid configuration file, you'll want to run your ffserver in the background (as a daemon), which can be accomplished using either a trailing ampersand character (&) in a shell command or more conveniently you can comment out "NoDaemon" directive inside your config file (works on Windows too).

Connecting your input sources

Once your ffserver is up and running, it's time to connect input sources to it. Without input sources, your ffserver is not going to broadcast anything to the outside world and will be pretty much useless. So, let's see how we can connect input sources to ffserver. The simplest way is to use the ffmpeg tool and the general syntax for such command is:

ffmpeg <inputs> <feed URL>

Of course, if you want to use one input source (ffmpeg) and bind it to multiple feeds (if you like to have only one application started), you might use:

ffmpeg <inputs> <feed URL> <more inputs> <another feed URL> <even more inputs> <yet another feed URL>

but, keep in mind that, if that input source crashes, all its bound feeds will become unavailable. So it's a good practice to use one input source (ffmpeg) pear each feed (1-1).

The parameter "<feed URL>" has got the following form:

http://<ffserver_ip_address_or_host_name>:<ffserver_port>/<feed_name>

All these things are defined in your ffserver configuration file:

• <ffserver_ip_address_or_host_name> - using the "BindAddress" directive
• <ffserver_port> - using the "Port" directive
• <feed_name> - using the "<Feed>" block

Let's assume that we want to stream our webcam video + audio to our friends. We will simply run an ffmpeg command line that will capture our webcam video and audio input and forward it to ffserver. The command line will look something like this:

ffmpeg \
	-f v4l2 -s 320x240 -r 25 -i /dev/video0 \
	-f alsa -ac 1 -i hw:0 \
	http://localhost:8090/feed1.ffm

This is the same thing as this:

ffmpeg -f v4l2 -s 320x240 -r 25 -i /dev/video0 -f alsa -ac 1 -i hw:0 http://localhost:8090/feed1.ffm

but it looks better and makes it more clear to understand each part of the command line.

• The first part "-f v4l2 -s 320x240 -r 25 -i /dev/video0" represents the first input for ffmpeg and captures our webcam video. For more info, you can read more about How to capture a webcam input.
• The second part "-f alsa -ac 1 -i hw:0" represents the second input for ffmpeg and captures our audio, depending on our system audio configuration. For more info, you can read more about Capturing audio with FFmpeg and ALSA.
• The last, but not the least important, part "http://localhost:8090/feed1.ffm" represents the feed URL, which tells ffmpeg to connect to ffserver and send it the audio + video streams for broadcast. In this example we used the hostname "localhost" which means that everything is running on our computer, but if you need to feed the live online ffserver, you'll need to change the "localhost" to the real host name or IP address of your ffserver computer. Also make sure that your feed name ends with ".ffm" and if it's not the case, then add "-f ffm" before your feed URL, to manually specify the output format (because ffmpeg won't be able to figure it out automatically any more), like this "-f ffm http://localhost:8090/blah.bleh".

As soon as you type the command above, you should see ffmpeg displaying some statistics about your input streams and counting output frames, which is a pretty good sign that everything works (so far).

For this example, you would need at least the following things defined in your config file (three dots "..." represent the other data that is irrelevant for this topic):

Port 8090
BindAddress 0.0.0.0

...

<Feed feed1.ffm>

	...

</Feed>

...

Viewing your streams

If you've done all the steps so far without errors, you're now ready to view your streams. The simplest way to do so is to use ffplay to connect to ffserver and view a specific stream. The general syntax for such command is:

ffplay <stream URL>

The parameter "<stream URL>" has got the following form:

http://<ffserver_ip_address_or_host_name>:<ffserver_port>/<stream_name>

All these things are defined in your ffserver configuration file:

• <ffserver_ip_address_or_host_name> - using the "BindAddress" directive
• <ffserver_port> - using the "Port" directive
• <stream_name> - using the "<Stream>" block

For example if you have appropriate stream element defined in your ffserver configuration file, you could type:

ffplay http://localhost:8090/test1.mpg

and your stream should appear (depending on the encoding used and caching enforced) relatively shortly in a matter of seconds. In this example we used the host name "localhost" which means that everything is running on our computer, but if you need to view streams from the live online ffserver, you'll need to change the "localhost" to the real host name or IP address of ffserver computer.

For this example, you would need at least the following things defined in your config file (three dots "..." represent the other data that is irrelevant for this topic):

Port 8090
BindAddress 0.0.0.0

...

<Stream test1.mpg>

	...

</Stream>

...

Creating the configuration file

It would be very wise to start off reading the ffserver's ​sample configuration file. It is self-documented with a lot of comments and it is a good starting point for beginners, since it contains various examples too. It would be a waste of time and space to write about it again here. Also, ​ffserver's documentation page might help too. In general, the configuration file is consisted of global directives, list of feed elements, list of stream elements and a specification of a special status stream element, which is used to provide a way for you to view the status of all your running streams.

Examples of configuration files

Streaming H.264 video with AAC audio in FLV format

Port 8090
BindAddress 0.0.0.0
MaxHTTPConnections 2000
MaxClients 1000
MaxBandwidth 1000
CustomLog -
#NoDaemon

<Feed feed1.ffm>
	File /tmp/feed1.ffm
	FileMaxSize 200K
	ACL allow 127.0.0.1
</Feed>

# if you want to use mpegts format instead of flv
# then change "live.flv" to "live.ts"
# and also change "Format flv" to "Format mpegts"
<Stream live.flv>
	Format flv
	Feed feed1.ffm

	VideoCodec libx264
	VideoFrameRate 30
	VideoBitRate 512
	VideoSize 320x240
	AVOptionVideo crf 23
	AVOptionVideo preset medium
	# for more info on crf/preset options, type: x264 --help
	AVOptionVideo flags +global_header

	AudioCodec aac
	Strict -2
	AudioBitRate 128
	AudioChannels 2
	AudioSampleRate 44100
	AVOptionAudio flags +global_header
</Stream>

##################################################################
# Special streams
##################################################################
<Stream stat.html>
	Format status
	# Only allow local people to get the status
	ACL allow localhost
	ACL allow 192.168.0.0 192.168.255.255
</Stream>

# Redirect index.html to the appropriate site
<Redirect index.html>
	URL http://www.ffmpeg.org/
</Redirect>
##################################################################

Streaming Theora video with Vorbis audio in Ogg format

Port 8090
BindAddress 0.0.0.0
MaxHTTPConnections 2000
MaxClients 1000
MaxBandwidth 1000
CustomLog -
#NoDaemon

<Feed feed1.ffm>
	File /tmp/feed1.ffm
	FileMaxSize 200K
	ACL allow 127.0.0.1
</Feed>

<Stream live.ogg>
	Format ogg
	Feed feed1.ffm

	VideoCodec libtheora
	VideoFrameRate 24
	VideoBitRate 512
	VideoSize 320x240
	VideoQMin 1
	VideoQMax 31
	VideoGopSize 12
	Preroll 0
	AVOptionVideo flags +global_header

	AudioCodec libvorbis
	AudioBitRate 64
	AudioChannels 2
	AudioSampleRate 44100
	AVOptionAudio flags +global_header
</Stream>

##################################################################
# Special streams
##################################################################
<Stream stat.html>
	Format status
	# Only allow local people to get the status
	ACL allow localhost
	ACL allow 192.168.0.0 192.168.255.255
</Stream>

# Redirect index.html to the appropriate site
<Redirect index.html>
	URL http://www.ffmpeg.org/
</Redirect>
##################################################################