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\input texinfo @c -*- texinfo -*-
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@settitle FFserver Documentation
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@titlepage
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@sp 7
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@center @titlefont{FFserver Documentation}
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@sp 3
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@end titlepage
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@chapter Introduction
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@c man begin DESCRIPTION
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FFserver is a streaming server for both audio and video. It supports
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several live feeds, streaming from files and time shifting on live feeds
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(you can seek to positions in the past on each live feed, provided you
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specify a big enough feed storage in ffserver.conf).
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FFserver runs in daemon mode by default; that is, it puts itself in
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the background and detaches from its TTY, unless it is launched in
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debug mode or a NoDaemon option is specified in the configuration
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file.
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This documentation covers only the streaming aspects of ffserver /
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ffmpeg. All questions about parameters for ffmpeg, codec questions,
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etc. are not covered here. Read @file{ffmpeg-doc.html} for more
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information.
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@section How does it work?
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FFserver receives prerecorded files or FFM streams from some ffmpeg
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instance as input, then streams them over RTP/RTSP/HTTP.
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An ffserver instance will listen on some port as specified in the
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configuration file. You can launch one or more instances of ffmpeg and
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send one or more FFM streams to the port where ffserver is expecting
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to receive them. Alternately, you can make ffserver launch such ffmpeg
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instances at startup.
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Input streams are called feeds, and each one is specified by a <Feed>
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section in the configuration file.
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For each feed you can have different output streams in various
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formats, each one specified by a <Stream> section in the configuration
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file.
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@section Status stream
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FFserver supports an HTTP interface which exposes the current status
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of the server.
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Simply point your browser to the address of the special status stream
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specified in the configuration file.
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For example if you have:
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@example
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<Stream status.html>
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Format status
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# Only allow local people to get the status
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ACL allow localhost
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ACL allow 192.168.0.0 192.168.255.255
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</Stream>
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@end example
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then the server will post a page with the status information when
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the special stream @file{status.html} is requested.
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@section What can this do?
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When properly configured and running, you can capture video and audio in real
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time from a suitable capture card, and stream it out over the Internet to
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either Windows Media Player or RealAudio player (with some restrictions).
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It can also stream from files, though that is currently broken. Very often, a
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web server can be used to serve up the files just as well.
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It can stream prerecorded video from .ffm files, though it is somewhat tricky
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to make it work correctly.
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@section What do I need?
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I use Linux on a 900 MHz Duron with a cheapo Bt848 based TV capture card. I'm
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using stock Linux 2.4.17 with the stock drivers. [Actually that isn't true,
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I needed some special drivers for my motherboard-based sound card.]
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I understand that FreeBSD systems work just fine as well.
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@section How do I make it work?
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First, build the kit. It *really* helps to have installed LAME first. Then when
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you run the ffserver ./configure, make sure that you have the
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@code{--enable-libmp3lame} flag turned on.
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LAME is important as it allows for streaming audio to Windows Media Player.
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Don't ask why the other audio types do not work.
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As a simple test, just run the following two command lines where INPUTFILE
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is some file which you can decode with ffmpeg:
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@example
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./ffserver -f doc/ffserver.conf &
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./ffmpeg -i INPUTFILE http://localhost:8090/feed1.ffm
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@end example
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At this point you should be able to go to your Windows machine and fire up
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Windows Media Player (WMP). Go to Open URL and enter
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@example
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    http://<linuxbox>:8090/test.asf
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@end example
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You should (after a short delay) see video and hear audio.
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WARNING: trying to stream test1.mpg doesn't work with WMP as it tries to
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transfer the entire file before starting to play.
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The same is true of AVI files.
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@section What happens next?
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You should edit the ffserver.conf file to suit your needs (in terms of
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frame rates etc). Then install ffserver and ffmpeg, write a script to start
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them up, and off you go.
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@section Troubleshooting
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@subsection I don't hear any audio, but video is fine.
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Maybe you didn't install LAME, or got your ./configure statement wrong. Check
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the ffmpeg output to see if a line referring to MP3 is present. If not, then
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your configuration was incorrect. If it is, then maybe your wiring is not
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set up correctly. Maybe the sound card is not getting data from the right
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input source. Maybe you have a really awful audio interface (like I do)
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that only captures in stereo and also requires that one channel be flipped.
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If you are one of these people, then export 'AUDIO_FLIP_LEFT=1' before
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starting ffmpeg.
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@subsection The audio and video loose sync after a while.
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Yes, they do.
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@subsection After a long while, the video update rate goes way down in WMP.
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Yes, it does. Who knows why?
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@subsection WMP 6.4 behaves differently to WMP 7.
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Yes, it does. Any thoughts on this would be gratefully received. These
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differences extend to embedding WMP into a web page. [There are two
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object IDs that you can use: The old one, which does not play well, and
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the new one, which does (both tested on the same system). However,
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I suspect that the new one is not available unless you have installed WMP 7].
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@section What else can it do?
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You can replay video from .ffm files that was recorded earlier.
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However, there are a number of caveats, including the fact that the
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ffserver parameters must match the original parameters used to record the
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file. If they do not, then ffserver deletes the file before recording into it.
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(Now that I write this, it seems broken).
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You can fiddle with many of the codec choices and encoding parameters, and
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there are a bunch more parameters that you cannot control. Post a message
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to the mailing list if there are some 'must have' parameters. Look in
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ffserver.conf for a list of the currently available controls.
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It will automatically generate the ASX or RAM files that are often used
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in browsers. These files are actually redirections to the underlying ASF
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or RM file. The reason for this is that the browser often fetches the
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entire file before starting up the external viewer. The redirection files
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are very small and can be transferred quickly. [The stream itself is
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often 'infinite' and thus the browser tries to download it and never
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finishes.]
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@section Tips
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* When you connect to a live stream, most players (WMP, RA, etc) want to
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buffer a certain number of seconds of material so that they can display the
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signal continuously. However, ffserver (by default) starts sending data
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in realtime. This means that there is a pause of a few seconds while the
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buffering is being done by the player. The good news is that this can be
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cured by adding a '?buffer=5' to the end of the URL. This means that the
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stream should start 5 seconds in the past -- and so the first 5 seconds
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of the stream are sent as fast as the network will allow. It will then
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slow down to real time. This noticeably improves the startup experience.
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You can also add a 'Preroll 15' statement into the ffserver.conf that will
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add the 15 second prebuffering on all requests that do not otherwise
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specify a time. In addition, ffserver will skip frames until a key_frame
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is found. This further reduces the startup delay by not transferring data
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that will be discarded.
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* You may want to adjust the MaxBandwidth in the ffserver.conf to limit
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the amount of bandwidth consumed by live streams.
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@section Why does the ?buffer / Preroll stop working after a time?
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It turns out that (on my machine at least) the number of frames successfully
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grabbed is marginally less than the number that ought to be grabbed. This
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means that the timestamp in the encoded data stream gets behind realtime.
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This means that if you say 'Preroll 10', then when the stream gets 10
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or more seconds behind, there is no Preroll left.
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Fixing this requires a change in the internals of how timestamps are
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handled.
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@section Does the @code{?date=} stuff work.
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Yes (subject to the limitation outlined above). Also note that whenever you
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start ffserver, it deletes the ffm file (if any parameters have changed),
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thus wiping out what you had recorded before.
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The format of the @code{?date=xxxxxx} is fairly flexible. You should use one
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of the following formats (the 'T' is literal):
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@example
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* YYYY-MM-DDTHH:MM:SS     (localtime)
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* YYYY-MM-DDTHH:MM:SSZ    (UTC)
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@end example
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You can omit the YYYY-MM-DD, and then it refers to the current day. However
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note that @samp{?date=16:00:00} refers to 16:00 on the current day -- this
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may be in the future and so is unlikely to be useful.
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You use this by adding the ?date= to the end of the URL for the stream.
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For example:   @samp{http://localhost:8080/test.asf?date=2002-07-26T23:05:00}.
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@c man end
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@chapter Invocation
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@section Syntax
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@example
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@c man begin SYNOPSIS
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ffserver [options]
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@c man end
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@end example
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@section Options
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@c man begin OPTIONS
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@table @option
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@include fftools-common-opts.texi
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@item -f @var{configfile}
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Use @file{configfile} instead of @file{/etc/ffserver.conf}.
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@item -n
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Enable no-launch mode. This option disables all the Launch directives
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within the various <Stream> sections. FFserver will not launch any
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ffmpeg instance, so you will have to launch them manually.
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@item -d
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Enable debug mode. This option increases log verbosity, directs log
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messages to stdout and causes ffserver to run in the foreground
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rather than as a daemon.
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@end table
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@c man end
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@ignore
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@setfilename ffserver
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@settitle FFserver video server
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@c man begin SEEALSO
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ffmpeg(1), ffplay(1), the @file{ffmpeg/doc/ffserver.conf} example and
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the HTML documentation of @file{ffmpeg}.
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@c man end
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@c man begin AUTHOR
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Fabrice Bellard
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@c man end
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@end ignore
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@bye