* These are my notes on streaming
[libav.git] / doc / HOWTO-STREAM
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1The FFserver streaming HOWTO
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3
4Philip Gladstone <philip-ffserver@gladstonefamily.net>
5Last updated: May 8, 2002
6
70. What is this HOWTO about?
8
9This covers only the streaming aspects of ffserver / ffmpeg. All questions about
10parameters for ffmpeg, codec questions, etc. are not covered here.
11
12You should also read the ffserver.txt file in this directory. It contains
13roughly the same information.
14
151. What can this do?
16
17When properly configured and running, you can capture video and audio in real
18time from a suitable capture card, and stream it out over the Internet to
19either Windows Media Player or RealAudio player (with some restrictions).
20
21It can also stream from files, though that is currently broken. Very often, a
22web server can be used to serve up the files just as well.
23
242. What do I need?
25
26I use Linux on a 900MHz Duron with a cheapo Bt848 based TV capture card. I'm
27using stock linux 2.4.17 with the stock drivers. [Actually that isn't true,
28I needed some special drivers from my motherboard based sound card.]
29
30I understand that FreeBSD systems work just fine as well.
31
323. How do I make it work?
33
34First, build the kit. It *really* helps to have installed LAME first. Then when
35you run the ffserver ./configure, make sure that you have the --enable-mp3lame
36flag turned on.
37
38LAME is important as it allows streaming of audio to Windows Media Player. Don't
39ask why the other audio types do not work.
40
41As a simple test, just run the following two command lines:
42
43./ffserver -f doc/ffserver.conf &
44./ffmpeg http://localhost:8090/feed1.ffm
45
46At this point you should be able to go to your windows machine and fire up
47Windows Media Player (WMP). Go to Open URL and enter
48
49 http://<linuxbox>:8090/test.asf
50
51You should see (after a short delay) video and hear audio.
52
534. What happens next?
54
55You should edit the ffserver.conf file to suit your needs (in terms of
56frame rates etc). Then install ffserver and ffmpeg, write a script to start
57them up, and off you go.
58
595. Troubleshooting
60
61* I don't hear any audio, but video is fine
62
63Maybe you didn't install LAME, or get your ./configure statement right. Check
64the ffmpeg output to see if a line referring to mp3 is present. If not, then
65your configuration was incorrect. If it is, then maybe your wiring is not
66setup correctly. Maybe the sound card is not getting data from the right
67input source. Maybe you have a really awful audio interface (like I do)
68that only captures in stereo and also requires that one channel be flipped.
69If you are one of these people, then export 'AUDIO_FLIP_LEFT=1' before
70starting ffmpeg.
71
72* The audio and video loose sync after a while.
73
74Yes, they do.
75
76* After a long while, the video update rate goes way down in WMP.
77
78Yes, it does. Who knows why?
79
806. What else can it do?
81
82There seems to be a bunch of code that allows you to replay previous
83video. I've never tried it, so it probably doesn't work properly. YMMV.
84In fact, in order to get some level of stability, ffserver now deletes
85all the previously sent video whenever it restarts.
86
87You can fiddle with many of the codec choices and encoding parameters, and
88there are a bunch more parameters that you cannot control. Post a message
89to the mailing list if there are some 'must have' parameters. Look in the
90ffserver.conf for a list of the currently available controls.
91
927. Tips
93
94* When you connect to a live stream, most players (WMP, RA etc) want to
95buffer a certain number of seconds of material so that they can display the
96signal continuously. However, ffserver (by default) starts sending data
97in real time. This means that there is a pause of a few seconds while the
98buffering is being done by the player. The good news is that this can be
99cured by adding a '?buffer=5' to the end of the URL. This says that the
100stream should start 5 seconds in the past -- and so the first 5 seconds
101of the stream is sent as fast as the network will allow. It will then
102slow down to real time. This noticeably improves the startup experience.