[Kde-kiosk] Artsd proxy for sound forward/multicast? (fwd)

[Tim Jansen]

On Friday 10 January 2003 16:57, Wout Mertens wrote:
> I am looking at providing a thin client architecture based on VNC, and one
> piece of the puzzle is missing: network transparant audio with variable
> endpoints.
> I know that arts can forward sound to a running artsd on some workstation,
> but that's not adequate, because, to change the location of the sound, you
> need to restart the application.

I would be careful with this solution, at least with longer audio 
transmissions and high quality sound. Please correct me if I am wrong, but 
AFAIK Arts uses a TCP-based protocol for uncompressed transmission. This has 
several disadvantages:
- CD-quality sound uses ca. 1.5 MBit/s. If you have several clients you will 
soon get problems in your network, even in a fast ethernet network, like 
collisions for example
- because Arts uses TCP, a lost packet (like one caused by a collision) will 
not result in omitting its content. Instead the TCP stack will, after waiting 
for a while, demand that the sender re-transmits the packet. This will cause 
a short gap in the sound (if the buffer isnt large enough) and delay the rest
- these gaps can add up. So if you had twenty 0.2 second delays, your sound 
has a 4 second delay

A more appropriate protocol to transmit audio would be RTP. AFAIK there are no 
RTP or comparable plugins for arts available though. Nor do I know any usable 
alternatives. Because of its architecture MAS 
(http://www.mediaapplicationserver.net/) could be quite interesting, but 
AFAIK they don't support this use case yet.


> A bonus would be that you can multicast artsd output...

Multicast requires UDP-based protocols (like RTP).

bye...