Updated to reflect the current state of ffserver (as I understand it).
[libav.git] / doc / ffserver-doc.texi
1 \input texinfo @c -*- texinfo -*-
3 @settitle FFserver Documentation
4 @titlepage
5 @sp 7
6 @center @titlefont{FFserver Documentation}
7 @sp 3
8 @end titlepage
11 @chapter Introduction
13 FFserver is a streaming server for both audio and video. It supports
14 several live feeds, streaming from files and time shifting on live feeds
15 (you can seek to positions in the past on each live feed, provided you
16 specify a big enough feed storage in ffserver.conf).
18 This documentation covers only the streaming aspects of ffserver /
19 ffmpeg. All questions about parameters for ffmpeg, codec questions,
20 etc. are not covered here. Read @file{ffmpeg-doc.[texi|html]} for more
21 information.
23 @chapter QuickStart
25 [Contributed by Philip Gladstone, philip-ffserver at gladstonefamily dot net]
27 @section What can this do?
29 When properly configured and running, you can capture video and audio in real
30 time from a suitable capture card, and stream it out over the Internet to
31 either Windows Media Player or RealAudio player (with some restrictions).
33 It can also stream from files, though that is currently broken. Very often, a
34 web server can be used to serve up the files just as well.
36 It can stream prerecorded video from .ffm files, though it is somewhat tricky
37 to make it work correctly.
39 @section What do I need?
41 I use Linux on a 900MHz Duron with a cheapo Bt848 based TV capture card. I'm
42 using stock linux 2.4.17 with the stock drivers. [Actually that isn't true,
43 I needed some special drivers from my motherboard based sound card.]
45 I understand that FreeBSD systems work just fine as well.
47 @section How do I make it work?
49 First, build the kit. It *really* helps to have installed LAME first. Then when
50 you run the ffserver ./configure, make sure that you have the --enable-mp3lame
51 flag turned on.
53 LAME is important as it allows streaming of audio to Windows Media Player. Don't
54 ask why the other audio types do not work.
56 As a simple test, just run the following two command lines (assuming that you
57 have a V4L video capture card):
59 @example
60 ./ffserver -f doc/ffserver.conf &
61 ./ffmpeg http://localhost:8090/feed1.ffm
62 @end example
64 At this point you should be able to go to your windows machine and fire up
65 Windows Media Player (WMP). Go to Open URL and enter
67 @example
68 http://<linuxbox>:8090/test.asf
69 @end example
71 You should see (after a short delay) video and hear audio.
73 WARNING: trying to stream test1.mpg doesn't work with WMP as it tries to
74 transfer the entire file before starting to play. The same is true of avi files.
76 @section What happens next?
78 You should edit the ffserver.conf file to suit your needs (in terms of
79 frame rates etc). Then install ffserver and ffmpeg, write a script to start
80 them up, and off you go.
82 @section Troubleshooting
84 @subsection I don't hear any audio, but video is fine
86 Maybe you didn't install LAME, or get your ./configure statement right. Check
87 the ffmpeg output to see if a line referring to mp3 is present. If not, then
88 your configuration was incorrect. If it is, then maybe your wiring is not
89 setup correctly. Maybe the sound card is not getting data from the right
90 input source. Maybe you have a really awful audio interface (like I do)
91 that only captures in stereo and also requires that one channel be flipped.
92 If you are one of these people, then export 'AUDIO_FLIP_LEFT=1' before
93 starting ffmpeg.
95 @subsection The audio and video loose sync after a while.
97 Yes, they do.
99 @subsection After a long while, the video update rate goes way down in WMP.
101 Yes, it does. Who knows why?
103 @subsection WMP 6.4 behaves differently to WMP 7.
105 Yes, it does. Any thoughts on this would be gratefully received. These
106 differences extend to embedding WMP into a web page. [There are two
107 different object ids that you can use, one of them -- the old one -- cannot
108 play very well, and the new one works well (both on the same system). However,
109 I suspect that the new one is not available unless you have installed WMP 7].
111 @section What else can it do?
113 You can replay video from .ffm files that was recorded earlier.
114 However, there are a number of caveats which include the fact that the
115 ffserver parameters must match the original parameters used to record the
116 file. If not, then ffserver deletes the file before recording into it. (Now I write
117 this, this seems broken).
119 You can fiddle with many of the codec choices and encoding parameters, and
120 there are a bunch more parameters that you cannot control. Post a message
121 to the mailing list if there are some 'must have' parameters. Look in the
122 ffserver.conf for a list of the currently available controls.
124 It will automatically generate the .ASX or .RAM files that are often used
125 in browsers. These files are actually redirections to the underlying .ASF
126 or .RM file. The reason for this is that the browser often fetches the
127 entire file before starting up the external viewer. The redirection files
128 are very small and can be transferred quickly. [The stream itself is
129 often 'infinite' and thus the browser tries to download it and never
130 finishes.]
132 @section Tips
134 * When you connect to a live stream, most players (WMP, RA etc) want to
135 buffer a certain number of seconds of material so that they can display the
136 signal continuously. However, ffserver (by default) starts sending data
137 in real time. This means that there is a pause of a few seconds while the
138 buffering is being done by the player. The good news is that this can be
139 cured by adding a '?buffer=5' to the end of the URL. This says that the
140 stream should start 5 seconds in the past -- and so the first 5 seconds
141 of the stream is sent as fast as the network will allow. It will then
142 slow down to real time. This noticeably improves the startup experience.
144 You can also add a 'Preroll 15' statement into the ffserver.conf that will
145 add the 15 second prebuffering on all requests that do not otherwise
146 specify a time. In addition, ffserver will skip frames until a key_frame
147 is found. This further reduces the startup delay by not transferring data
148 that will be discarded.
150 * You may want to adjust the MaxBandwidth in the ffserver.conf to limit
151 the amount of bandwidth consumed by live streams.
153 @section Why does the ?buffer / Preroll stop working after a time?
155 It turns out that (on my machine at least) the number of frames successfully
156 grabbed is marginally less than the number that ought to be grabbed. This
157 means that the timestamp in the encoded data stream gets behind real time.
158 This means that if you say 'preroll 10', then when the stream gets 10
159 or more seconds behind, there is no preroll left.
161 Fixing this requires a change in the internals in how timestamps are
162 handled.
164 @section Does the @code{?date=} stuff work.
166 Yes (subject to the caution above). Also note that whenever you start
167 ffserver, it deletes the ffm file (if any parameters have changed), thus wiping out what you had recorded
168 before.
170 The format of the @code{?date=xxxxxx} is fairly flexible. You should use one
171 of the following formats (the 'T' is literal):
173 @example
174 * YYYY-MM-DDTHH:MM:SS (localtime)
176 @end example
178 You can omit the YYYY-MM-DD, and then it refers to the current day. However
179 note that @samp{?date=16:00:00} refers to 4PM on the current day -- this may be
180 in the future and so unlikely to useful.
182 You use this by adding the ?date= to the end of the URL for the stream.
183 For example: @samp{http://localhost:8080/test.asf?date=2002-07-26T23:05:00}.
185 @bye