From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Henningsson Subject: Re: Delay calculations for USB audio? Date: Fri, 28 Sep 2012 13:56:44 +0200 Message-ID: <5065907C.8030904@canonical.com> References: <5065834E.4010707@canonical.com> <506588A2.4070602@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from youngberry.canonical.com (youngberry.canonical.com [91.189.89.112]) by alsa0.perex.cz (Postfix) with ESMTP id 075FC26172E for ; Fri, 28 Sep 2012 13:56:43 +0200 (CEST) In-Reply-To: <506588A2.4070602@gmail.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: "Gabriel M. Beddingfield" Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org On 09/28/2012 01:23 PM, Gabriel M. Beddingfield wrote: > On 09/28/2012 06:00 AM, David Henningsson wrote: >> (Oh, and btw, if you have an idea of the crackling/distorted USB audio, >> let me know. I'm using a standard Logitech USB Headset, using >> speaker-test -c 2 -D plughw:Headset -t sine -r 48000 >> I can make the problem go away using any of these options: >> * Booting a 3.2 kernel - I've tried 3.5, 3.6-rc7 and 3.2 >> * Choosing the 44100 sample rate instead of the default of 48000 >> * Selecting the outer USB port instead of the inner one. Yes, there >> are two USB ports next to each other, and this only happens on one of >> them. (!)) > > The last statement sounds like you're sharing a hub with another device > that has reserved bandwidth. For example, a USB webcam will often do > this. Audio will work for a while and then get pre-empted. > > Use 'lsusb -t' to view your USB layout. Thanks! Indeed, when deactivating bluetooth (in both kernel 3.2 and 3.5) the sound is back to normal, so this time I could actually get the distortion out of 3.2 as well. Question is - is this an actual hardware limitation, or is it actually fixable if we wrote better drivers? -- David Henningsson, Canonical Ltd. https://launchpad.net/~diwic