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Daemon
Premium
join:2003-06-29
Berkeley, CA
Reviews:
·Comcast
·webpass.net
reply to stoli412

Re: iOS 5: Airplay to multiple speakers?

We have an AP Express in all of the common rooms in our house, connected via the 'extend this network' feature of the Airports.

As is, the traffic overhead is fairly extreme and much more than I'd suspect for a simple audio stream. I don't think Apple is making much use of multicasting. Thus, when I'm in my kitchen and activate airplay in the kitchen on the phone, it seems as though the audio stream goes kitchen AP-->Living room AP-->Host AP Extreme connected to modem-->Living room AP-->kitchen AP for playback.

Because it has to go through the living room twice, wirelessly, but the AP only has one antenna, it ends up halving the bandwidth and the stream ends up stuttering.

As a result, I end up streaming using the remote app, as my computer is wired into the Airport Extreme and the network path appears to be merely unidirectional.

Instead, the iPhone should use multicasting broadcast, and just send a few packets here and there to tell a specific AP to start listening. It gets more complicated if one of the destination APs is out of range, but at least with my suggested setup the number of network paths is severely reduced.

Because they aren't using multicasting, apparently, the reason the phone probably only supports one set of speakers is because the CPU doesn't have enough power to simultaneously process and send multiple audio streams over the network at once.
--
-Ryan
I use Linux, OS X, iOS and Windows. Let the OS wars die.


bobrk
You kids get offa my lawn
Premium
join:2000-02-02
San Jose, CA
Reviews:
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Indeed, we get stuttering even using Remote from the main Mac with all our music. It pretty much went away when we got a Time Capsule (with an Airport Extreme inside), but now, after 22 months, the wireless has died, but that's a story for another thread.

stoli412

join:2003-02-12
UK
reply to Daemon
Most of the stuff in my house is hardwired via powerline ethernet. The only truly wireless devices are the MBPs, iPads, and iPhones. We have a wifi router downstairs and upstairs. The AppleTVs, Airport Express, Pioneer Receiver, etc are all connected via ethernet, so I don't see very much stuttering.

I do agree that AirPlay needs to multicast. I'm surprised it doesn't work this way already!

kitsune

join:2001-11-26
Sacramento, CA
reply to Daemon
Have you tried it with the AExp set to just join instead of extend? If you don't actually need the extra coverage, extending the network just reduces your total bandwidth because part of it is needed to maintain the dynamic WDS you are using. Which usually causes stuttering in the audio stream. Not to mention it also puts more load on the AExp's CPU.

Daemon
Premium
join:2003-06-29
Berkeley, CA
Reviews:
·Comcast
·webpass.net
said by kitsune:

Have you tried it with the AExp set to just join instead of extend? If you don't actually need the extra coverage, extending the network just reduces your total bandwidth because part of it is needed to maintain the dynamic WDS you are using. Which usually causes stuttering in the audio stream. Not to mention it also puts more load on the AExp's CPU.

We used to do that with the older version Express that didn't support extend. It didn't make much of a difference, which was surprising.

The 'extend this network' feature is a proprietary Apple feature that is not the same as WDS. WDS does not support 802.11n, multiple frequencies simultaneously, or WPA like extend this network does. It is supposed to have a much lower overhead than WDS, apparently down to about 10% versus 50%.

We need the full network coverage in the kitchen, so we have it setup as a full AP.

The older Express is actually attached via wire to an Airport Extreme, both in the living room, with the Extreme extending the larger network. The express then doesn't allow wireless clients.
--
-Ryan
I use Linux, OS X, iOS and Windows. Let the OS wars die.