[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 @section What do I need?
38 I use Linux on a 900MHz Duron with a cheapo Bt848 based TV capture card. I'm
39 using stock linux 2.4.17 with the stock drivers. [Actually that isn't true,
40 I needed some special drivers from my motherboard based sound card.]
42 I understand that FreeBSD systems work just fine as well.
44 @section How do I make it work?
46 First, build the kit. It *really* helps to have installed LAME first. Then when
47 you run the ffserver ./configure, make sure that you have the --enable-mp3lame
48 flag turned on.
50 LAME is important as it allows streaming of audio to Windows Media Player. Don't
51 ask why the other audio types do not work.
53 As a simple test, just run the following two command lines:
55 @example
56 ./ffserver -f doc/ffserver.conf &
57 ./ffmpeg http://localhost:8090/feed1.ffm
58 @end example
60 At this point you should be able to go to your windows machine and fire up
61 Windows Media Player (WMP). Go to Open URL and enter
63 @example
64 http://<linuxbox>:8090/test.asf
65 @end example
67 You should see (after a short delay) video and hear audio.
69 WARNING: trying to stream test1.mpg doesn't work with WMP as it tries to
70 transfer the entire file before starting to play.
72 @section What happens next?
74 You should edit the ffserver.conf file to suit your needs (in terms of
75 frame rates etc). Then install ffserver and ffmpeg, write a script to start
76 them up, and off you go.
78 @section Troubleshooting
80 @subsection I don't hear any audio, but video is fine
82 Maybe you didn't install LAME, or get your ./configure statement right. Check
83 the ffmpeg output to see if a line referring to mp3 is present. If not, then
84 your configuration was incorrect. If it is, then maybe your wiring is not
85 setup correctly. Maybe the sound card is not getting data from the right
86 input source. Maybe you have a really awful audio interface (like I do)
87 that only captures in stereo and also requires that one channel be flipped.
88 If you are one of these people, then export 'AUDIO_FLIP_LEFT=1' before
89 starting ffmpeg.
91 @subsection The audio and video loose sync after a while.
93 Yes, they do.
95 @subsection After a long while, the video update rate goes way down in WMP.
97 Yes, it does. Who knows why?
99 @subsection WMP 6.4 behaves differently to WMP 7.
101 Yes, it does. Any thoughts on this would be gratefully received. These
102 differences extend to embedding WMP into a web page. [There are two
103 different object ids that you can use, one of them -- the old one -- cannot
104 play very well, and the new one works well (both on the same system). However,
105 I suspect that the new one is not available unless you have installed WMP 7].
107 @section What else can it do?
109 There seems to be a bunch of code that allows you to replay previous
110 video. I've never tried it, so it probably doesn't work properly. YMMV.
111 In fact, in order to get some level of stability, ffserver now deletes
112 all the previously sent video whenever it restarts.
114 You can fiddle with many of the codec choices and encoding parameters, and
115 there are a bunch more parameters that you cannot control. Post a message
116 to the mailing list if there are some 'must have' parameters. Look in the
117 ffserver.conf for a list of the currently available controls.
119 It will automatically generate the .ASX or .RAM files that are often used
120 in browsers. These files are actually redirections to the underlying .ASF
121 or .RM file. The reason for this is that the browser often fetches the
122 entire file before starting up the external viewer. The redirection files
123 are very small and can be transferred quickly. [The stream itself is
124 often 'infinite' and thus the browser tries to download it and never
125 finishes.]
127 @section Tips
129 * When you connect to a live stream, most players (WMP, RA etc) want to
130 buffer a certain number of seconds of material so that they can display the
131 signal continuously. However, ffserver (by default) starts sending data
132 in real time. This means that there is a pause of a few seconds while the
133 buffering is being done by the player. The good news is that this can be
134 cured by adding a '?buffer=5' to the end of the URL. This says that the
135 stream should start 5 seconds in the past -- and so the first 5 seconds
136 of the stream is sent as fast as the network will allow. It will then
137 slow down to real time. This noticeably improves the startup experience.
139 You can also add a 'Preroll 15' statement into the ffserver.conf that will
140 add the 15 second prebuffering on all requests that do not otherwise
141 specify a time. In addition, ffserver will skip frames until a key_frame
142 is found. This further reduces the startup delay by not transferring data
143 that will be discarded.
145 * You may want to adjust the MaxBandwidth in the ffserver.conf to limit
146 the amount of bandwidth consumed by live streams.
148 @section Why does the ?buffer / Preroll stop working after a time?
150 It turns out that (on my machine at least) the number of frames successfully
151 grabbed is marginally less than the number that ought to be grabbed. This
152 means that the timestamp in the encoded data stream gets behind real time.
153 This means that if you say 'preroll 10', then when the stream gets 10
154 or more seconds behind, there is no preroll left.
156 Fixing this requires a require in the internals in how timestampts are
157 handled.
159 @section Does the @code{?date=} stuff work.
161 Yes (subject to the caution above). Also note that whenever you start
162 ffserver, it deletes the ffm file, thus wiping out what you had recorded
163 before. This behaviour is a temporary fix to various crashes. The aim is
164 to fix it so that the old data is saved if possible.
166 The format of the @code{?date=xxxxxx} is fairly flexible. You should use one
167 of the following formats (the 'T' is literal):
169 @example
170 * YYYY-MM-DDTHH:MM:SS (localtime)
172 @end example
174 You can omit the YYYY-MM-DD, and then it refers to the current day. However
175 note that @samp{?date=16:00:00} refers to 4PM on the current day -- this may be
176 in the future and so unlikely to useful.
178 You use this by adding the ?date= to the end of the URL for the stream.
179 For example: @samp{http://localhost:8080/test.asf?date=2002-07-26T23:05:00}.
181 @bye