PDA

View Full Version : Wireless streaming of 16bit, 44.1k



Ben Cook
2004-12-06, 04:05
I asked this question a few months ago when I first bought a SB. I seem to
remeber that the data rate doubles, triples etc each time you add another
device, even when they are synced.

I was originally running my SB on a 802.11G access point with FLAC and found
that I got drop-outs when surfing the net, using the web interface or just
copying files to/from the server. So I bought a 2nd hand 802.11B AP (eBay
20) just for the SB and all is fine now.

I haven't bought a second SB (yet...) so can't answer your other question.

Ben.

> -----Original Message-----
> From: discuss-bounces (AT) lists (DOT) slimdevices.com
> [mailto:discuss-bounces (AT) lists (DOT) slimdevices.com]On Behalf Of JJ
> Sent: 05 December 2004 06:21
> To: Slim Devices Discussion
> Subject: [slim] Wireless streaming of 16bit, 44.1k
>
>
> I received my Squeezebox a couple of days ago and I've been playing with
> it, learning a little about how it and the software work, and generally
> having a blast. :-)
>
> I'm considering a second, maybe even a third player and was giving some
> thought to doing synched playback on multiple players. My music
> collection is stored as compressed FLAC files. My understanding is that
> FLAC files are decoded at the Slim server and the uncompressed 16bit,
> 44.1k WAV is then streamed across the network to the Squeezebox.
> A single
> stereo redbook stream works out to a little under 1.5Mbps. When doing
> synched streaming to multiple boxes, does this double, then triple, etc.
> or does it remain at 1.5Mbps?
>
> Obviously streaming different files to different Squeezeboxes on the
> wireless network would require increasing amounts of bandwidth. What
> would be the practical limit to the number Squeezeboxes that can be
> operated at the same time on an 802.11b network when streaming WAV/FLAC
> files?
>
>

JJ
2004-12-06, 17:19
----- Original Message -----
From: "Ben Cook" <ben (AT) bencook (DOT) net>
To: "Slim Devices Discussion" <discuss (AT) lists (DOT) slimdevices.com>
Sent: Monday, December 06, 2004 4:05 AM
Subject: [slim] Wireless streaming of 16bit, 44.1k


> I asked this question a few months ago when I first bought a SB. I seem
> to remeber that the data rate doubles, triples etc each time you add
> another
> device, even when they are synced.


Thanks. If anyone has a definitive answer on this, I'd appreciate it. I
really don't know enough about IP protocols or how SlimServer does synched
playback, but I thought maybe some sort of IP 'broadcast' might be
utilized that wouldn't compound the bandwidth used.


> I was originally running my SB on a 802.11G access point with FLAC and
> found
> that I got drop-outs when surfing the net, using the web interface or
> just
> copying files to/from the server. So I bought a 2nd hand 802.11B AP
> (eBay
> 20) just for the SB and all is fine now.


I was thinking the same thing - having a dedicated wireless music network
for multiple wireless Squeezeboxes would make sense given the limited
bandwidth of 802.11b. I suppose you could even have multiple wireless
networks if necessary, so long as you had the appropriate routing in place
so that a single server could communicate with all of them at the same
time.

In some other forums I'm hearing a lot about people having problems with
dropout with just a single wireless Squeezebox. I suspect bandwdith used
by surfing is partly the cause, along with insufficient processing power
on the server (probably being used for the same web surfing). Even so, if
_one_ stream is so often problematic then it suggests that running
multiple devices could be too much for 802.11b.

kdf
2004-12-06, 18:11
Quoting JJ <jj (AT) zolx (DOT) com>:

> ----- Original Message -----
> From: "Ben Cook" <ben (AT) bencook (DOT) net>
> To: "Slim Devices Discussion" <discuss (AT) lists (DOT) slimdevices.com>
> Sent: Monday, December 06, 2004 4:05 AM
> Subject: [slim] Wireless streaming of 16bit, 44.1k
>
>
> > I asked this question a few months ago when I first bought a SB. I seem
> > to remeber that the data rate doubles, triples etc each time you add
> > another
> > device, even when they are synced.
>
>
> Thanks. If anyone has a definitive answer on this, I'd appreciate it. I
> really don't know enough about IP protocols or how SlimServer does synched
> playback, but I thought maybe some sort of IP 'broadcast' might be
> utilized that wouldn't compound the bandwidth used.

Currently, each player has its own stream. Sync just means that the streams are
matches up at the start of each song. Support for multicast has been mentioned
a few times as one option, but I am unaware of an effort to implement that at
this time.

> > I was originally running my SB on a 802.11G access point with FLAC and
> > found
> > that I got drop-outs when surfing the net, using the web interface or
> > just
> > copying files to/from the server. So I bought a 2nd hand 802.11B AP
> > (eBay
> > 20) just for the SB and all is fine now.
>
>
> I was thinking the same thing - having a dedicated wireless music network
> for multiple wireless Squeezeboxes would make sense given the limited
> bandwidth of 802.11b. I suppose you could even have multiple wireless
> networks if necessary, so long as you had the appropriate routing in place
> so that a single server could communicate with all of them at the same
> time.
>
> In some other forums I'm hearing a lot about people having problems with
> dropout with just a single wireless Squeezebox. I suspect bandwdith used
> by surfing is partly the cause, along with insufficient processing power
> on the server (probably being used for the same web surfing). Even so, if
> _one_ stream is so often problematic then it suggests that running
> multiple devices could be too much for 802.11b.

While this is true for those that have severe problems with dropouts, it is also
possible to not have any dropouts. I have run two wireless squeezeboxen with
FLAC and they've been fine. I have a third on wireless but I think its reach
too far in teh range to be as useful. Signal strenth is often about 60%, but
occasionally will take a sudden dive to near 10% and drop the server for a
length of time. This can happen even when not playing music. This player is
simply a victom of some outside influence.

I'm running a dual B/G network becuase I have an iBook that can run G. I have
noticed it is much faster than B, but that it too suffers from the occasional
slowdown even for simple web traffic. I'm uncertain that a squeezebox via a
wireless G gateway would necessarily make you immune to dropouts either. It
should, however, at least be a marked improvement. G is still teh same channels
inside teh 2.4GHz band as B, so it is victim to the same interference.

-kdf

Jack Coates
2004-12-06, 19:42
> ----- Original Message -----
> From: "Ben Cook" <ben (AT) bencook (DOT) net>
> To: "Slim Devices Discussion" <discuss (AT) lists (DOT) slimdevices.com>
> Sent: Monday, December 06, 2004 4:05 AM
> Subject: [slim] Wireless streaming of 16bit, 44.1k
>
>
>> I asked this question a few months ago when I first bought a SB. I seem
>> to remeber that the data rate doubles, triples etc each time you add
>> another
>> device, even when they are synced.
>
>
> Thanks. If anyone has a definitive answer on this, I'd appreciate it. I
> really don't know enough about IP protocols or how SlimServer does synched
> playback, but I thought maybe some sort of IP 'broadcast' might be
> utilized that wouldn't compound the bandwidth used.
>

you're thinking of multicast. It's been discussed, but IIRC would require
firmware changes and would drop SliMP3's off the wagon.

>
>> I was originally running my SB on a 802.11G access point with FLAC and
>> found
>> that I got drop-outs when surfing the net, using the web interface or
>> just
>> copying files to/from the server. So I bought a 2nd hand 802.11B AP
>> (eBay
>> 20) just for the SB and all is fine now.
>
>
> I was thinking the same thing - having a dedicated wireless music network
> for multiple wireless Squeezeboxes would make sense given the limited
> bandwidth of 802.11b. I suppose you could even have multiple wireless
> networks if necessary, so long as you had the appropriate routing in place
> so that a single server could communicate with all of them at the same
> time.
>
> In some other forums I'm hearing a lot about people having problems with
> dropout with just a single wireless Squeezebox. I suspect bandwdith used
> by surfing is partly the cause, along with insufficient processing power
> on the server (probably being used for the same web surfing). Even so, if
> _one_ stream is so often problematic then it suggests that running
> multiple devices could be too much for 802.11b.
>

Interference is actually the problem most of the time IMHO. A clean
wireless signal is plenty of bandwidth. A wireless signal that's sharing
frequency with a few cordless phones and microwaves while the hardware
struggles with WEP decryption is going to have some problems.

--
Jack At Monkeynoodle.Org: It's A Scientific Venture...
"Believe what you're told; there'd be chaos if everyone thought for
themselves." -- Top Dog hotdog stand, Berkeley, CA

Carsten Bormann
2004-12-10, 11:41
>> Thanks. If anyone has a definitive answer on this, I'd appreciate
>> it. I
>> really don't know enough about IP protocols or how SlimServer does
>> synched
>> playback, but I thought maybe some sort of IP 'broadcast' might be
>> utilized that wouldn't compound the bandwidth used.
>>
>
> you're thinking of multicast. It's been discussed, but IIRC would
> require
> firmware changes and would drop SliMP3's off the wagon.

Folks,

it's time for my yearly post about this.
Multicast over wireless is not necessarily the answer here.

First, 802.11 access points use a special multicast rate (sometimes
called "basic rate") instead of the unicast rate for
multicast/broadcast.
This needs to be selected in such a way that *all* stations can be
reached -- there can't be rate adaptation for multicast.
Normally, the multicast rate is configured to be *much* lower than
unicast; in an 802.11 b/g network it is likely to be 2 Mbit/s.
To obtain reasonable multicast rates, people would have to
significantly re-configure their wireless networks, and then they would
wonder why their laptops don't properly DHCP/ARP any longer in the
fringes.

As an additional, minor point, with multicast you are losing the
retransmit at the link layer (assuming the multicast is from AP to
station, which will be the usual case here).

Second, you need to replace TCP with a reliable multicast protocol. A
good one is available now (NORM, defined in RFC3940/3941), but we are
talking about an order of magnitude more code (and, as a result, more
bugs) here. And I can tell you that multicast protocols can be
fiendishly hard to debug...

So, unless Slim wants to address a specific market that really needs
this (i.e., dedicated, specially configured music WLANs so there are no
problems with laptops at the fringes), I'd stay out of this if I had to
make the decision. (I've been working on various multicast protocols
for more than a decade now, and they have great uses, but Slim does not
strike me as one.)

Gruesse, Carsten

Jack Coates
2004-12-10, 22:35
>>> Thanks. If anyone has a definitive answer on this, I'd appreciate
>>> it. I
>>> really don't know enough about IP protocols or how SlimServer does
>>> synched
>>> playback, but I thought maybe some sort of IP 'broadcast' might be
>>> utilized that wouldn't compound the bandwidth used.
>>>
>>
>> you're thinking of multicast. It's been discussed, but IIRC would
>> require
>> firmware changes and would drop SliMP3's off the wagon.
>
> Folks,
>
> it's time for my yearly post about this.
> Multicast over wireless is not necessarily the answer here.
<fascinating info snipped>

thanks for the writeup, I'll try to remember it this time :) Kind of odd
that the technology which inspired multicast (radio) is unable to actually
do it, though I think I understand why (Ethernet requires bidirectionally
synchronous behavior within the CSMA/CD bus, unlike AM or FM, so it
doesn't map well to a sphere of rapidly decreasing signal strength).
--
Jack At Monkeynoodle.Org: It's A Scientific Venture...
"Believe what you're told; there'd be chaos if everyone thought for
themselves." -- Top Dog hotdog stand, Berkeley, CA