Return-path: Received: from mga14.intel.com ([143.182.124.37]:40831 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1765065AbZDAO3F convert rfc822-to-8bit (ORCPT ); Wed, 1 Apr 2009 10:29:05 -0400 From: "Guy, Wey-Yi W" To: Kalle Valo , Johannes Berg CC: Dan Williams , linux-wireless , Matthew Garrett , Marcel Holtmann Date: Wed, 1 Apr 2009 07:29:01 -0700 Subject: RE: more thoughts on power saving (was: wireless powersaving (in NM?)) Message-ID: (sfid-20090401_162909_624541_23BD8722) References: <1237891149.4320.73.camel@johannes.local> <1238583879.5970.195.camel@johannes.local> <87zlf0hbk4.fsf@litku.valot.fi> In-Reply-To: <87zlf0hbk4.fsf@litku.valot.fi> Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: If I understand correctly, based on implementation, if VoIP support silence detection (which most of the codec support it), it will not constantly sending packets; that might be the reason for bad quality. Wey-Yi Guy Intel Corporation 2111 N.E. 25th Avenue M/S JF3-308 Hillsboro OR 97124-5961 USA Work Phone: 503-264-6023 (OR) Cell Phone: 503-329-8410 Email: wey-yi.w.guy@intel.com -----Original Message----- From: Kalle Valo [mailto:kalle.valo@gmail.com] On Behalf Of Kalle Valo Sent: Wednesday, April 01, 2009 4:13 AM To: Johannes Berg Cc: Dan Williams; Guy, Wey-Yi W; linux-wireless; Matthew Garrett; Marcel Holtmann Subject: Re: more thoughts on power saving (was: wireless powersaving (in NM?)) Johannes Berg writes: > Hi, > > So I had a few more thoughts. > > Let me start with a story :) > > I use my N810 device for landline calls via SIP these days. > Every time I'm in a call, audio is very choppy and I can barely > understand the person I'm talking to -- my fix is to "ping -i > 0.05" the device to disable its powersaving... > > > Now, why is audio choppy? I was blaming it on the wireless powersaving, > and disabling that clearly fixes it. But is the problem really just > there? I think it might also be the application -- its playback buffer > is smaller than the networking latency I am experiencing due to > wireless. I think I could probably tolerate an additional audio latency > of 150ms (my beacon interval being 102.4ms) or so, if audio wasn't > choppy. What's the DTIM count in your AP? N810 wakes up only for DTIM beacons, that might increase the latency. > That means the application (telepathy sofiasip I guess) would have > to have 150ms or so playback buffer to make the playback smooth with > delay. [1] [...] > [1] I don't quite see why this doesn't happen automatically, it seems it > must discard packets that don't fit into its idea of the stream timing N810 only disables the power save when there's a frame to transmit. I guess the SIP connection isn't constantly sending anything and that's why you get bad quality. -- Kalle Valo