ffserver man page on aLinux

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FFSERVER(1)							   FFSERVER(1)

NAME
       ffserver - FFserver video server

SYNOPSIS
       ffserver [options]

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, pro‐
       vided 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 / ffm‐
       peg. All questions about parameters for ffmpeg, codec questions, etc.
       are not covered here. Read ffmpeg-doc.html for more information.

       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 con‐
       figuration 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.

       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:

	       <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>

       then the server will post a page with the status information when the
       special stream status.html is requested.

       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.

       What do I need?

       I use Linux on a 900MHz 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.

       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
       "--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 INPUT‐
       FILE is some file which you can decode with ffmpeg:

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

       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

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

       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.

       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.

       Troubleshooting

       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 get‐
       ting 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.

       The audio and video loose sync after a while.

       Yes, they do.

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

       Yes, it does. Who knows why?

       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].

       What else can it do?

       You can replay video from .ffm files that was recorded earlier.	How‐
       ever, 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 record‐
       ing 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.]

       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 dis‐
       play 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 net‐
       work 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 other‐
       wise 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.

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

       It turns out that (on my machine at least) the number of frames suc‐
       cessfully 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.

       Does the "?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 "?date=xxxxxx" is fairly flexible. You should use one
       of the following formats (the 'T' is literal):

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

       You can omit the YYYY-MM-DD, and then it refers to the current day.
       However note that ?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:   http://localhost:8080/test.asf?date=2002-07-26T23:05:00.

OPTIONS
       -version
	   Show version.

       -L  Show license.

       -formats
	   Show available formats, codecs, protocols, ...

       -h  Show help.

       -f configfile
	   Use configfile instead of /etc/ffserver.conf.

       -n  Enable no-launch mode. This option disables all the Launch direc‐
	   tives within the various <Stream> sections. FFserver will not
	   launch any ffmpeg instance, so you will have to launch them manu‐
	   ally.

       -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.

SEE ALSO
       ffmpeg(1), ffplay(1), the ffmpeg/doc/ffserver.conf example and the HTML
       documentation of ffmpeg.

AUTHOR
       Fabrice Bellard

				  2008-08-28			   FFSERVER(1)
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