From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Hofman Subject: Re: Capture from 3+ cards connected to a USB hub - distorted samples Date: Wed, 14 Dec 2011 13:19:00 +0100 Message-ID: <4EE89434.9040609@ivitera.com> References: <4EE29877.2050804@ivitera.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from cable.insite.cz (static-84-242-75-189.net.upcbroadband.cz [84.242.75.189]) by alsa0.perex.cz (Postfix) with ESMTP id 75F37103822 for ; Wed, 14 Dec 2011 13:19:00 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by cable.insite.cz (Postfix) with ESMTP id 41DFFA1A40B07 for ; Wed, 14 Dec 2011 13:18:59 +0100 (CET) Received: from cable.insite.cz ([84.242.75.189]) by localhost (server.insite.cz [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id k4igvPgsF62k for ; Wed, 14 Dec 2011 13:18:59 +0100 (CET) Received: from [192.168.1.20] (sara.insite.cz [192.168.1.20]) (Authenticated sender: pavel) by cable.insite.cz (Postfix) with ESMTPSA id 2D3D1A1A32346 for ; Wed, 14 Dec 2011 13:18:59 +0100 (CET) In-Reply-To: <4EE29877.2050804@ivitera.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: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org Dne 10.12.2011 00:23, Pavel Hofman napsal(a): > Hi, > > I have been informed about the following problem which I was able to > reproduce afterwards: > > * Latest git.alsa-project.org drivers > > * USB 2.0 hub, 3 or more USB soundcards (inexpensive USB sticks, USB > audio v.1 types, async capture, adaptive playback) hooked to the hub, > identified A, B, C, D. > > * NONE of these soundcards is playing back > > Now: > > * Card A begins microphone capturing (mono 48/16), result OK > > * Card B begins capturing (mono 48/16), both results still OK > > * As soon as the third card C begins capturing, the signal captured from > cards A and B gets distorted. Audacity shows some samples are > incorrect, distorting the expected sine waveform of the testing signal. > I can provide screenshots as well as recorded samples, if needed. > > * The signal recorded from card C is OK. > > BUT > > * If any card hooked to the HUB is playing back (even a fourth one D), > the distortion does not occur. It happens only when there is no playback > stream going through the hub. Traffic on another USB port has no effect, > in fact the test signal for the three cards was provided by a > multichannel USB card hooked to another USB port. > > It seems to me as if blocks of samples for each card in the USB frame > sometimes overlap by a few bits, corrupting the neighbouring card > samples, or are recovered incorrectly. > > I understand I have provided no real data, I am ready to do so plus any > tests you would consider useful. > > Thanks a lot for suggestions of the next debugging steps I should do. > Hi, please may I ask for help? I think we could fix this likely bug. Thanks a lot, Pavel.