* Updated with new stream configuration items
[libav.git] / doc / HOWTO-STREAM
1 The FFserver streaming HOWTO
2 ----------------------------
4 Philip Gladstone <philip-ffserver@gladstonefamily.net>
5 Last updated: May 10, 2002
7 0. What is this HOWTO about?
9 This covers only the streaming aspects of ffserver / ffmpeg. All questions about
10 parameters for ffmpeg, codec questions, etc. are not covered here.
12 You should also read the ffserver.txt file in this directory. It contains
13 roughly the same information.
15 1. What can this do?
17 When properly configured and running, you can capture video and audio in real
18 time from a suitable capture card, and stream it out over the Internet to
19 either Windows Media Player or RealAudio player (with some restrictions).
21 It can also stream from files, though that is currently broken. Very often, a
22 web server can be used to serve up the files just as well.
24 2. What do I need?
26 I use Linux on a 900MHz Duron with a cheapo Bt848 based TV capture card. I'm
27 using stock linux 2.4.17 with the stock drivers. [Actually that isn't true,
28 I needed some special drivers from my motherboard based sound card.]
30 I understand that FreeBSD systems work just fine as well.
32 3. How do I make it work?
34 First, build the kit. It *really* helps to have installed LAME first. Then when
35 you run the ffserver ./configure, make sure that you have the --enable-mp3lame
36 flag turned on.
38 LAME is important as it allows streaming of audio to Windows Media Player. Don't
39 ask why the other audio types do not work.
41 As a simple test, just run the following two command lines:
43 ./ffserver -f doc/ffserver.conf &
44 ./ffmpeg http://localhost:8090/feed1.ffm
46 At this point you should be able to go to your windows machine and fire up
47 Windows Media Player (WMP). Go to Open URL and enter
49 http://<linuxbox>:8090/test.asf
51 You should see (after a short delay) video and hear audio.
53 4. What happens next?
55 You should edit the ffserver.conf file to suit your needs (in terms of
56 frame rates etc). Then install ffserver and ffmpeg, write a script to start
57 them up, and off you go.
59 5. Troubleshooting
61 * I don't hear any audio, but video is fine
63 Maybe you didn't install LAME, or get your ./configure statement right. Check
64 the ffmpeg output to see if a line referring to mp3 is present. If not, then
65 your configuration was incorrect. If it is, then maybe your wiring is not
66 setup correctly. Maybe the sound card is not getting data from the right
67 input source. Maybe you have a really awful audio interface (like I do)
68 that only captures in stereo and also requires that one channel be flipped.
69 If you are one of these people, then export 'AUDIO_FLIP_LEFT=1' before
70 starting ffmpeg.
72 * The audio and video loose sync after a while.
74 Yes, they do.
76 * After a long while, the video update rate goes way down in WMP.
78 Yes, it does. Who knows why?
80 * WMP 6.4 behaves differently to WMP 7.
82 Yes, it does. Any thoughts on this would be gratefully received. These
83 differences extend to embedding WMP into a web page. [There are two
84 different object ids that you can use, one of them -- the old one -- cannot
85 play very well, and the new one works well (both on the same system). However,
86 I suspect that the new one is not available unless you have installed WMP 7].
88 6. What else can it do?
90 There seems to be a bunch of code that allows you to replay previous
91 video. I've never tried it, so it probably doesn't work properly. YMMV.
92 In fact, in order to get some level of stability, ffserver now deletes
93 all the previously sent video whenever it restarts.
95 You can fiddle with many of the codec choices and encoding parameters, and
96 there are a bunch more parameters that you cannot control. Post a message
97 to the mailing list if there are some 'must have' parameters. Look in the
98 ffserver.conf for a list of the currently available controls.
100 It will automatically generate the .ASX or .RAM files that are often used
101 in browsers. These files are actually redirections to the underlying .ASF
102 or .RM file. The reason for this is that the browser often fetches the
103 entire file before starting up the external viewer. The redirection files
104 are very small and can be transferred quickly. [The stream itself is
105 often 'infinite' and thus the browser tries to download it and never
106 finishes.]
108 7. Tips
110 * When you connect to a live stream, most players (WMP, RA etc) want to
111 buffer a certain number of seconds of material so that they can display the
112 signal continuously. However, ffserver (by default) starts sending data
113 in real time. This means that there is a pause of a few seconds while the
114 buffering is being done by the player. The good news is that this can be
115 cured by adding a '?buffer=5' to the end of the URL. This says that the
116 stream should start 5 seconds in the past -- and so the first 5 seconds
117 of the stream is sent as fast as the network will allow. It will then
118 slow down to real time. This noticeably improves the startup experience.
120 You can also add a 'Preroll 15' statement into the ffserver.conf that will
121 add the 15 second prebuffering on all requests that do not otherwise
122 specify a time. In addition, ffserver will skip frames until a key_frame
123 is found. This further reduces the startup delay by not transferring data
124 that will be discarded.
126 * You may want to adjust the MaxBandwidth in the ffserver.conf to limit
127 the amount of bandwidth consumed by live streams.