mirror of
https://git.ffmpeg.org/ffmpeg.git
synced 2024-12-14 19:25:01 +00:00
ce83897796
Originally committed as revision 825 to svn://svn.ffmpeg.org/ffmpeg/trunk
162 lines
6.6 KiB
Plaintext
162 lines
6.6 KiB
Plaintext
The FFserver streaming HOWTO
|
|
----------------------------
|
|
|
|
Philip Gladstone <philip-ffserver@gladstonefamily.net>
|
|
Last updated: July 26, 2002
|
|
|
|
0. What is this HOWTO about?
|
|
|
|
This covers only the streaming aspects of ffserver / ffmpeg. All questions about
|
|
parameters for ffmpeg, codec questions, etc. are not covered here.
|
|
|
|
You should also read the ffserver.txt file in this directory. It contains
|
|
roughly the same information.
|
|
|
|
1. 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.
|
|
|
|
2. 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 from my motherboard based sound card.]
|
|
|
|
I understand that FreeBSD systems work just fine as well.
|
|
|
|
3. 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-mp3lame
|
|
flag turned on.
|
|
|
|
LAME is important as it allows streaming of 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:
|
|
|
|
./ffserver -f doc/ffserver.conf &
|
|
./ffmpeg 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 see (after a short delay) 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.
|
|
|
|
4. 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.
|
|
|
|
5. Troubleshooting
|
|
|
|
* I don't hear any audio, but video is fine
|
|
|
|
Maybe you didn't install LAME, or get your ./configure statement right. 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
|
|
setup correctly. Maybe the sound card is not getting 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
|
|
different object ids that you can use, one of them -- the old one -- cannot
|
|
play very well, and the new one works well (both on the same system). However,
|
|
I suspect that the new one is not available unless you have installed WMP 7].
|
|
|
|
6. What else can it do?
|
|
|
|
There seems to be a bunch of code that allows you to replay previous
|
|
video. I've never tried it, so it probably doesn't work properly. YMMV.
|
|
In fact, in order to get some level of stability, ffserver now deletes
|
|
all the previously sent video whenever it restarts.
|
|
|
|
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 the
|
|
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.]
|
|
|
|
7. 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 display the
|
|
signal continuously. However, ffserver (by default) starts sending data
|
|
in real time. 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 says that the
|
|
stream should start 5 seconds in the past -- and so the first 5 seconds
|
|
of the stream is sent as fast as the network 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 otherwise
|
|
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.
|
|
|
|
8. Why does the ?buffer / Preroll stop working after a time?
|
|
|
|
It turns out that (on my machine at least) the number of frames successfully
|
|
grabbed is marginally less than the number that ought to be grabbed. This
|
|
means that the timestamp in the encoded data stream gets behind real time.
|
|
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 require in the internals in how timestampts are
|
|
handled.
|
|
|
|
9. Does the ?date= stuff work.
|
|
|
|
Yes (subject to the caution above). Also note that whenever you start
|
|
ffserver, it deletes the ffm file, thus wiping out what you had recorded
|
|
before. This behaviour is a temporary fix to various crashes. The aim is
|
|
to fix it so that the old data is saved if possible.
|
|
|
|
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 4PM on the current day -- this may be
|
|
in the future and so unlikely to 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
|