From mboxrd@z Thu Jan 1 00:00:00 1970 From: "kunal@singhkunal.com" Subject: bandwidth issue with usb-audio in alsa Date: Tue, 27 May 2008 00:23:18 -0400 Message-ID: <380-22008522742318173@M2W010.mail2web.com> Reply-To: kunal@singhkunal.com Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Received: from xsmtp08.mail2web.com (xsmtp08.mail2web.com [168.144.250.208]) by alsa0.perex.cz (Postfix) with ESMTP id 08B0C248F2 for ; Tue, 27 May 2008 06:23:20 +0200 (CEST) Received: from [168.144.108.10] (helo=M2W010.mail2web.com) by xsmtp08.mail2web.com with smtp (Exim 4.63) (envelope-from ) id 1K0qiU-0003WF-85 for alsa-devel@alsa-project.org; Tue, 27 May 2008 00:23:19 -0400 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: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org Hi, My Platform ------------- I am trying to stream audio data from a USB-device (an iPod) to my arm-based embedded device (running kernel 2.6.23). The USB-device confirms to usb digital audio (subclass - streaming) class. The endpoint buffer size 196 bytes and transfer period is 1 msec. So, I should be reading data every msec. Problem ----------- I am facing some bandwidth issues. The data is not being captured fast enough. I notice that once one set of URBs are captured (one set equal to MAX_URBS), there is a significant delay in capturing the next set of URBs. = I have set MAX_URBS equal to 32. When I connect a USB-Analyzer and analyze the timings, I can see that 32 URBs are captured at a interval of 1 msec each. After that there is a break of around 250 msec. And then again 32 URBs captured in sequence. If I change the MAX_URBs to any other value N, N URBs get captured at interval of 1 msec each, and then there is a break. Can some one suggest a way to improve this problem. Is there some configuration or parameter which I can change, so that URBs get submitted fast enough? May be as soon as the old one has retired. Thanks and Regards, Kunal www.singhkunal.com = -------------------------------------------------------------------- mail2web.com =96 What can On Demand Business Solutions do for you? http://link.mail2web.com/Business/SharePoint