From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kunal Singh Subject: Re: bandwidth issue with usb-audio in alsa Date: Tue, 27 May 2008 18:40:31 +0530 Message-ID: <483C0847.1080405@singhkunal.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from outbound-mail-35.bluehost.com (outbound-mail-35.bluehost.com [69.89.18.155]) by alsa0.perex.cz (Postfix) with SMTP id 3F991243BC for ; Tue, 27 May 2008 15:10:39 +0200 (CEST) Received: from [122.167.44.165] (helo=[127.0.0.1]) by host100.hostmonster.com with esmtpa (Exim 4.68) (envelope-from ) id 1K0ywm-0001Yi-Oi for alsa-devel@alsa-project.org; Tue, 27 May 2008 07:10:37 -0600 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, I have some update on the issue which I had reported earlier. In my last e-mail, I had not mentioned that iPod is connected to the target through a USB (HS) Hub. When I connect the same hub to my Desktop and read its configuration using "usbview" - I see that "interval" for this hub is mentioned as "256 msec". (I have two hubs and I get all the results same with both the hubs). With 36 URBs, the gap between two set of transactions is appx 220 msec (220+36 => 256). So, I am wondering if the problem which I am seeing is because the external hub. I can not connect iPod directly to my target board, because this board does not support enough current (as needed by iPod). Can some one suggest, where is the problem - is it with the host controller driver? Regards, Kunal Singh ----------------------------- Kunal Singh wrote: 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