[vlc] Re: Wireless Multicast Stream

Galen galen at myhome.net
Sat Nov 20 17:50:51 CET 2004


I have mostly D-Link products (yeah, yeah...) and am relatively happy. 
Multicasting works perfectly. I even tested three simultaneous, 
uncompressed CD-quality audio streams without problems for roughly 12 
hours. Never seen a problem.

I did, however, have to make sure my firmware was up to date and adjust 
a few settings. I wireless APs like to throttle/block/tweak 
multicasting messages by default, so it's best to fix that. And as the 
earlier poster said, the multicast rate should be adjusted according to 
your signal levels around the wireless network.

That's my 2¢...

-Galen

On Nov 19, 2004, at 2:35 PM, Benjamin PRACHT wrote:

> On Sat, Nov 20, 2004, Eftychios Eftychiou wrote :
>> Can someone recommend a specific Wireless router that will multicast a
>> video stream effectively? I know the Dlink 624 will not allow any 
>> mutlicast
>> traffic to the wireless AP.
>>
>> Thanks
>>
>> Eftychios
>>
>
> Well, I'v successfully streamed about 6Mbit/s of udp multicast traffic
> on a Symbol Spectrum 24 AP 4131 11 Mbit/s Access Point with an
> acceptable packet loss (I haven't tried with other hardware). However,
> don't expect it to work out of the box (default settings give about
> a 10 kbit/s bitrate). Indeed, the layer 2 part or the 802.11 norm
> wasn't really designed for broadcast of high rate streams. Broadcast
> / Multicast frames are sent using the lowest available transfer rate
> available on the AP (1 Mbit/s by default), so that every endpoint, even
> those who are at the limit of the range can receive them. Moreover,
> for energy saving reasons, broadcast / multicast frames are only sent
> every so called DTIM intervals (every 0.3-1s by default on most AP).
> Indeed, every node of a wireless network is supposed to wake up at such
> intervals, to receive broadcast frames. As a consequence, broadcast
> frames have to be buffered in the AP between 2 DTIM.
>
> So, to make short, to improve the multicast bandwidth on an AP:
>
> - Increase the rate the minimum available bandwidth of your AP (at the
>   cost of range of the AP
> - Increase the size of the buffer allowed for broadcast / multicast
>   frames (not all AP offer this feature, the Symbol one did)
> - Decrease the interval between 2 DTIM (send one every beacon, for
>   instance) at the cost of the power consumption of the nodes on the
>   network...
>
> -- 
> BigBen
>
> -- 
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