Re: [linux-audio-dev] FreeBSD 5.4-RELEASE

Chris Camisa wrote:

>Hello!
>
> Sorry if I'm starting in the wrong place, but after several months
>of thinking and two weeks of working, I have a couple of questions.
>
> 1.) can FreeBSD 5.4-RELEASE operate without a sound card such that the
>Network Audio Server allows applications running on it to have sound
>heard on other speakers on the network?
>
>
depends how the audio server works. Since it's a network audio server I
assume the answer is yes.

> a.) I have "device sound" compiled into the custom kernel
> b.) the NASD gives an error about connecting to a block device
>when I try to start NASD.
>
>
> 2.) is arts the way to go with ALSA? When KDE starts on my 2.6 kernel
>Gentoo system the sound suddenly get louder, as if a new mixer takes
>over and bumps the master volume as KDE 3.3 loads.
>
>
arts is the soundserver of KDE but if you want low latency and rock
solid operation then use jackd: http://jackit.sf.net

The sound bump is because KDE restores the mixer settings.

> 3.) What is the preferred method to have multiple x86 computers
>playing the same stream of sound simultaneously? (within a few dozen
>milliseconds)
>
> a.) all the servers have NTP capability and mplayer/xine
>
>
this is tricky and not trivial to implement.
Why do you need multiple machines playing the same sound ?
If you need sample accurate sync I suggest you to use one machine with
multiple audio outs.
Otherwise you can use multiple machines but you need to write an
application that synchronizes
the start of the audio files/streams. A few dozen of msecs should be
achievable.
But keep in mind if the machines play in the same room then a few dozen
of msecs means you will
hear a flanging effect.

> 4.) How do I have several x86 FreeBSD/linux machines all synchronize
>video also? Is that simply XF86 Forwarding?
>
>
X11 forwarding sucks for video since the video stream travels
uncompressed over the network.
100Mbit networks aren't capable to transmit full motion (eg full PAL
704x576 x 25 fps) video.
You would need 1Gbit networks and I think it would put too much strain
on the machines since
X11 forwarding is not designed for forwarding video.

What you could do is use libxine and write your own player that triggers
the start of videos
using eg an UDP socket.
Or alternatively you could set up a multicast video streaming server,
VLC ( http://www.videolan.org ) has one
and let the video players play the multicast stream.
This should provide perfect synchronization since the "clock" is given
by the streaming server.

cheers,
Benno
http://www.linuxsampler.org
Received on Sun Jun 5 04:15:06 2005