avserver video server
see also :
avconv - avplay - avprobe
add an example, a script, a trick and tips
no example yet ...
... Feel free to add your own example above to help other Linux-lovers !
avserver is unmaintained, largely broken and in need of a
complete rewrite. It probably won’t work for you. Use
at your own risk.
avserver is a
streaming server for both audio and video. It supports
several live feeds, streaming from files and time shifting
on live feeds (you can seek to positions in the past on each
live feed, provided you specify a big enough feed storage in
in daemon mode by default; that is, it puts itself in the
background and detaches from its TTY , unless
it is launched in debug mode or a NoDaemon option is
specified in the configuration file.
documentation covers only the streaming aspects of avserver
/ avconv. All questions about parameters for avconv, codec
questions, etc. are not covered here. Read
avconv.html for more information.
How does it
avserver receives prerecorded files or FFM
streams from some avconv instance as input, then streams
them over RTP/RTSP/HTTP .
instance will listen on some port as specified in the
configuration file. You can launch one or more instances of
avconv and send one or more FFM streams to
the port where avserver is expecting to receive them.
Alternately, you can make avserver launch such avconv
instances at startup.
are called feeds, and each one is specified by a
<Feed> section in the configuration file.
For each feed
you can have different output streams in various formats,
each one specified by a <Stream> section in the
avserver supports an HTTP interface which
exposes the current status of the server.
your browser to the address of the special status stream
specified in the configuration file.
For example if
# Only allow local people to get the status
ACL allow localhost
ACL allow 192.168.0.0 192.168.255.255
then the server
will post a page with the status information when the
special stream status.html is requested.
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
It can stream
prerecorded video from .ffm files, though it is somewhat
tricky to make it work correctly.
What do I
I use Linux on a 900 MHz 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 for my motherboard-based
that FreeBSD systems work just fine as well.
How do I
make it work?
First, build the kit. It *really* helps to have installed
LAME first. Then when you run the avserver
./configure, make sure that you have the
flag turned on.
is important as it allows for streaming audio to Windows
Media Player. Don’t ask why the other audio types do
As a simple
test, just run the following two command lines where
INPUTFILE is some file which you can decode
./avserver -f doc/avserver.conf &
./avconv -i INPUTFILE 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
(after a short delay) see video and hear audio.
trying to stream test1.mpg doesn’t work with
WMP as it tries to transfer the entire file
before starting to play. The same is true of
You should edit the avserver.conf file to suit your needs
(in terms of frame rates etc). Then install avserver and
avconv, write a script to start them up, and off you go.
I don’t hear any audio, but video is fine.
didn’t install LAME , or got your
./configure statement wrong. Check the avconv 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 set up 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 avconv.
and video lose sync after a while.
After a long
while, the video update rate goes way down in
Yes, it does.
Who knows why?
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 object IDs that you can use: The
old one, which does not play well, and the new one, which
does (both tested on the same system). However, I suspect
that the new one is not available unless you have installed
can it do?
You can replay video from .ffm files that was recorded
earlier. However, there are a number of caveats, including
the fact that the avserver parameters must match the
original parameters used to record the file. If they do not,
then avserver deletes the file before recording into it.
(Now that I write this, it seems broken).
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 avserver.conf
for a list of the currently available controls.
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.]
* 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, avserver (by
default) starts sending data in realtime. 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 means that the stream should start
5 seconds in the past -- and so the first 5 seconds of the
stream are sent as fast as the network will allow. It will
then slow down to real time. This noticeably improves the
You can also
add a ’Preroll 15’ statement into the
avserver.conf that will add the 15 second prebuffering on
all requests that do not otherwise specify a time. In
addition, avserver 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 avserver.conf to limit the
amount of bandwidth consumed by live streams.
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 realtime.
This means that if you say ’Preroll 10’, then
when the stream gets 10 or more seconds behind, there is no
requires a change in the internals of how timestamps are
"?date=" stuff work.
Yes (subject to the limitation outlined above). Also note
that whenever you start avserver, it deletes the ffm file
(if any parameters have changed), thus wiping out what you
had recorded before.
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 16:00 on
the current day -- this may be in the future and so is
unlikely to be useful.
You use this by
adding the ?date= to the end of the URL for
the stream. For example:
numerical options, if not specified otherwise, accept in
input a string representing a number, which may contain one
of the International System number postfixes, for example
’K’, ’M’, ’G’. If
’i’ is appended after the postfix, powers of 2
are used instead of powers of 10. The ’B’
postfix multiplies the value for 8, and can be appended
after another postfix or used alone. This allows using for
example ’ KB ’,
’MiB’, ’G’ and ’B’ as
do not take arguments are boolean options, and set the
corresponding value to true. They can be set to false by
prefixing with "no" the option name, for example
using "-nofoo" in the command line will set
to false the boolean option with name "foo".
Some options are applied per-stream, e.g. bitrate or codec.
Stream specifiers are used to precisely specify which
stream(s) does a given option belong to.
specifier is a string generally appended to the option name
and separated from it by a colon. E.g.
"-codec:a:1 ac3" option contains
"a:1" stream specifer, which matches the
second audio stream. Therefore it would select the ac3 codec
for the second audio stream.
specifier can match several stream, the option is then
applied to all of them. E.g. the stream specifier in
"-b:a 128k" matches all audio
An empty stream
specifier matches all streams, for example
"-codec copy" or
"-codec: copy" would copy all the
streams without reencoding.
of stream specifiers are:
Matches the stream with this
index. E.g. "-threads:1 4" would
set the thread count for the second stream to 4.
stream_type is one of:
’v’ for video, ’a’ for audio,
’s’ for subtitle, ’d’ for data and
’t’ for attachments. If stream_index is
given, then matches stream number stream_index of
this type. Otherwise matches all streams of this type.
If stream_index is
given, then matches stream number stream_index in
program with id program_id. Otherwise matches all
streams in this program.
These options are shared amongst the av* tools.
Show available formats.
preceding the format names have the following meanings:
Show available codecs.
preceding the codec names have the following meanings:
Codec supports slices
Codec supports direct rendering
Codec can handle input truncated at random locations
instead of only at frame boundaries
Show available bitstream
Show available protocols.
Show available libavfilter
Show available pixel
Show available sample
loglevel | -v loglevel
Set the logging level used by
the library. loglevel is a number or a string
containing one of the following values:
By default the
program logs to stderr, if coloring is supported by the
terminal, colors are used to mark errors and warnings. Log
coloring can be disabled setting the environment variable
NO_COLOR , or can be forced setting
the environment variable
AV_LOG_FORCE_COLOR . The use of the
environment variable NO_COLOR is
deprecated and will be dropped in a following Libav
These options are provided directly by the libavformat,
libavdevice and libavcodec libraries. To see the list of
available AVOptions, use the -help option. They
are separated into two categories:
These options can be set for
any container, codec or device. Generic options are listed
under AVFormatContext options for containers/devices and
under AVCodecContext options for codecs.
These options are specific to
the given container, device or codec. Private options are
listed under their corresponding
For example to
write an ID3v2.3 header instead of a default ID3v2.4 to an
MP3 file, use the id3v2_version
private option of the MP3 muxer:
avconv -i input.flac -id3v2_version 3 out.mp3
AVOptions are obviously per-stream, so the chapter on stream
specifiers applies to them
-nooption syntax cannot be used for boolean
AVOptions, use -option 0/-option
undocumented way of specifying per-stream AVOptions by
prepending v/a/s to the options name is now obsolete and
will be removed soon.
Use configfile instead
Enable no-launch mode. This option disables all the
Launch directives within the various <Stream>
sections. Since avserver will not launch any avconv
instances, you will have to launch them manually.
Enable debug mode. This option increases log verbosity,
directs log messages to stdout and causes avserver to run in
the foreground rather than as a daemon.
avplay , avprobe , the
avserver.conf example and the Libav