From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Henningsson Subject: Re: USB Audio questions Date: Tue, 16 Aug 2011 07:30:53 +0200 Message-ID: <4E4A008D.60907@canonical.com> References: <1313432124-22591-1-git-send-email-lars@metafoo.de> <1313432124-22591-2-git-send-email-lars@metafoo.de> <000001cc5b8a$4a6577c0$df306740$@bossart@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" 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 8FA1C24575 for ; Tue, 16 Aug 2011 07:30:57 +0200 (CEST) In-Reply-To: <000001cc5b8a$4a6577c0$df306740$@bossart@linux.intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Pierre-Louis Bossart Cc: 'ALSA Development Mailing List' List-Id: alsa-devel@alsa-project.org On 08/15/2011 10:31 PM, Pierre-Louis Bossart wrote: > - Increasing the number of packets/urbs solves my power issue but not the > synchronization issue. If I reduce the number of urbs to reduce the > interrupt rate, then the accuracy of the hw_pointer is decreased big time > and it becomes difficult to synchronize with video. I think the same thing is a problem for quite a few other devices as well - I wonder if we need some kind of "pointer granularity" variable to be exported through the ALSA API? PulseAudio could use that to determine whether or not to enable timer-based scheduling. And in these cases, maybe a call to hw_pointer could return hw_pointer and time, and then PulseAudio etc could use that for extrapolation (or the extrapolation could be done in alsa-lib). -- David Henningsson, Canonical Ltd. http://launchpad.net/~diwic