\input texinfo @c -*- texinfo -*-

 @settitle ffserver Documentation

 @titlepage

 @center @titlefont{ffserver Documentation}

 @end titlepage

 @top
 
 @contents
 

 @chapter Synopsys
 
 The generic syntax is:
 
 @example
 @c man begin SYNOPSIS
 ffserver [options]
 @c man end
 @end example

 @chapter Description

 @c man begin DESCRIPTION

 ffserver is a streaming server for both audio and video. It supports

 several live feeds, streaming from files and time shifting on live feeds
 (you can seek to positions in the past on each live feed, provided you
 specify a big enough feed storage in ffserver.conf).

 ffserver runs in daemon mode by default; that is, it puts itself in

 the background and detaches from its TTY, unless it is launched in
 debug mode or a NoDaemon option is specified in the configuration
 file.
 

 This documentation covers only the streaming aspects of ffserver /
 ffmpeg. All questions about parameters for ffmpeg, codec questions,

 etc. are not covered here. Read @file{ffmpeg.html} for more

 information.
 

 @section How does it work?
 

 ffserver receives prerecorded files or FFM streams from some ffmpeg

 instance as input, then streams them over RTP/RTSP/HTTP.
 
 An ffserver instance will listen on some port as specified in the
 configuration file. You can launch one or more instances of ffmpeg and
 send one or more FFM streams to the port where ffserver is expecting
 to receive them. Alternately, you can make ffserver launch such ffmpeg
 instances at startup.
 
 Input streams are called feeds, and each one is specified by a <Feed>
 section in the configuration file.
 
 For each feed you can have different output streams in various
 formats, each one specified by a <Stream> section in the configuration
 file.
 

 @section Status stream
 

 ffserver supports an HTTP interface which exposes the current status

 of the server.
 
 Simply point your browser to the address of the special status stream
 specified in the configuration file.
 
 For example if you have:
 @example
 <Stream status.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>
 @end example
 
 then the server will post a page with the status information when
 the special stream @file{status.html} is requested.
 

 @section What can this do?

 
 When properly configured and running, you can capture video and audio in real
 time from a suitable capture card, and stream it out over the Internet to
 either Windows Media Player or RealAudio player (with some restrictions).
 
 It can also stream from files, though that is currently broken. Very often, a
 web server can be used to serve up the files just as well.
 

 It can stream prerecorded video from .ffm files, though it is somewhat tricky
 to make it work correctly.
 

 @section What do I need?

 I use Linux on a 900 MHz Duron with a cheapo Bt848 based TV capture card. I'm

 using stock Linux 2.4.17 with the stock drivers. [Actually that isn't true,
 I needed some special drivers for my motherboard-based sound card.]

 
 I understand that FreeBSD systems work just fine as well.
 

 @section How do I make it work?

 
 First, build the kit. It *really* helps to have installed LAME first. Then when

 you run the ffserver ./configure, make sure that you have the
 @code{--enable-libmp3lame} flag turned on.

 LAME is important as it allows for streaming audio to Windows Media Player.

 Don't ask why the other audio types do not work.

 As a simple test, just run the following two command lines where INPUTFILE
 is some file which you can decode with ffmpeg:

 @example

 ffserver -f doc/ffserver.conf &
 ffmpeg -i INPUTFILE http://localhost:8090/feed1.ffm

 @end example

 At this point you should be able to go to your Windows machine and fire up

 Windows Media Player (WMP). Go to Open URL and enter

 @example

     http://<linuxbox>:8090/test.asf

 @end example

 You should (after a short delay) see video and hear audio.

 WARNING: trying to stream test1.mpg doesn't work with WMP as it tries to

 transfer the entire file before starting to play.
 The same is true of AVI files.

 @section What happens next?

 You should edit the ffserver.conf file to suit your needs (in terms of

 frame rates etc). Then install ffserver and ffmpeg, write a script to start
 them up, and off you go.
 

 @section Troubleshooting

 @subsection I don't hear any audio, but video is fine.

 Maybe you didn't install LAME, or got your ./configure statement wrong. Check
 the ffmpeg output to see if a line referring to MP3 is present. If not, then

 your configuration was incorrect. If it is, then maybe your wiring is not

 set up correctly. Maybe the sound card is not getting data from the right

 input source. Maybe you have a really awful audio interface (like I do)

 that only captures in stereo and also requires that one channel be flipped.
 If you are one of these people, then export 'AUDIO_FLIP_LEFT=1' before

 starting ffmpeg.
 

 @subsection The audio and video lose sync after a while.

 
 Yes, they do.
 

 @subsection After a long while, the video update rate goes way down in WMP.

 
 Yes, it does. Who knows why?
 

 @subsection WMP 6.4 behaves differently to WMP 7.

 
 Yes, it does. Any thoughts on this would be gratefully received. These
 differences extend to embedding WMP into a web page. [There are two

 object IDs that you can use: The old one, which does not play well, and
 the new one, which does (both tested on the same system). However,

 I suspect that the new one is not available unless you have installed WMP 7].
 

 @section What else can it do?

 You can replay video from .ffm files that was recorded earlier.

 However, there are a number of caveats, including the fact that the

 ffserver parameters must match the original parameters used to record the

 file. If they do not, then ffserver deletes the file before recording into it.

 (Now that I write this, it seems broken).

 
 You can fiddle with many of the codec choices and encoding parameters, and
 there are a bunch more parameters that you cannot control. Post a message

 to the mailing list if there are some 'must have' parameters. Look in

 ffserver.conf for a list of the currently available controls.
 

 It will automatically generate the ASX or RAM files that are often used
 in browsers. These files are actually redirections to the underlying ASF
 or RM file. The reason for this is that the browser often fetches the

 entire file before starting up the external viewer. The redirection files
 are very small and can be transferred quickly. [The stream itself is

 often 'infinite' and thus the browser tries to download it and never

 finishes.]
 

 @section Tips

 * When you connect to a live stream, most players (WMP, RA, etc) want to

 buffer a certain number of seconds of material so that they can display the
 signal continuously. However, ffserver (by default) starts sending data

 in realtime. This means that there is a pause of a few seconds while the

 buffering is being done by the player. The good news is that this can be

 cured by adding a '?buffer=5' to the end of the URL. This means that the

 stream should start 5 seconds in the past -- and so the first 5 seconds

 of the stream are sent as fast as the network will allow. It will then

 slow down to real time. This noticeably improves the startup experience.

 
 You can also add a 'Preroll 15' statement into the ffserver.conf that will
 add the 15 second prebuffering on all requests that do not otherwise
 specify a time. In addition, ffserver will skip frames until a key_frame
 is found. This further reduces the startup delay by not transferring data
 that will be discarded.
 
 * You may want to adjust the MaxBandwidth in the ffserver.conf to limit
 the amount of bandwidth consumed by live streams.

 @section Why does the ?buffer / Preroll stop working after a time?

 
 It turns out that (on my machine at least) the number of frames successfully
 grabbed is marginally less than the number that ought to be grabbed. This

 means that the timestamp in the encoded data stream gets behind realtime.
 This means that if you say 'Preroll 10', then when the stream gets 10
 or more seconds behind, there is no Preroll left.

 Fixing this requires a change in the internals of how timestamps are

 handled.
 

 @section Does the @code{?date=} stuff work.

 Yes (subject to the limitation outlined above). Also note that whenever you
 start ffserver, it deletes the ffm file (if any parameters have changed),

 thus wiping out what you had recorded before.

 The format of the @code{?date=xxxxxx} is fairly flexible. You should use one

 of the following formats (the 'T' is literal):
 

 @example

 * YYYY-MM-DDTHH:MM:SS     (localtime)
 * YYYY-MM-DDTHH:MM:SSZ    (UTC)

 @end example

 You can omit the YYYY-MM-DD, and then it refers to the current day. However

 note that @samp{?date=16:00:00} refers to 16:00 on the current day -- this
 may be in the future and so is unlikely to be useful.

 
 You use this by adding the ?date= to the end of the URL for the stream.

 For example:   @samp{http://localhost:8080/test.asf?date=2002-07-26T23:05:00}.

 @c man end

 @chapter Options

 @c man begin OPTIONS

 @include avtools-common-opts.texi

 @section Main options
 

 @table @option

 @item -f @var{configfile}

 Use @file{configfile} instead of @file{/etc/ffserver.conf}.

 @item -n
 Enable no-launch mode. This option disables all the Launch directives

 within the various <Stream> sections. Since ffserver will not launch
 any ffmpeg instances, you will have to launch them manually.

 @item -d
 Enable debug mode. This option increases log verbosity, directs log

 messages to stdout and causes ffserver to run in the foreground

 rather than as a daemon.

 @end table
 @c man end
 
 @ignore
 

 @setfilename ffserver

 @settitle ffserver video server

 
 @c man begin SEEALSO

 ffmpeg(1), ffplay(1), ffprobe(1), the @file{ffserver.conf}

 example and the FFmpeg HTML documentation

 @c man end
 

 @c man begin AUTHORS

 The FFmpeg developers

 @c man end
 
 @end ignore
 

 @bye