From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jelle de Jong Subject: Re: Stuttering 100mA and 500mA MaxPower usb audio investigation on bus powered and external powererd usb hubs Date: Sun, 09 Nov 2008 16:55:31 +0100 Message-ID: <491707F3.4070806@powercraft.nl> References: <4915FCF8.9040703@powercraft.nl> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from node04.cambriumhosting.nl (node04.cambriumhosting.nl [217.19.16.165]) by alsa0.perex.cz (Postfix) with ESMTP id 85981103815 for ; Sun, 9 Nov 2008 16:55:35 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by node04.cambriumhosting.nl (Postfix) with ESMTP id E3345B0000E1 for ; Sun, 9 Nov 2008 16:55:34 +0100 (CET) Received: from node04.cambriumhosting.nl ([127.0.0.1]) by localhost (node04.cambriumhosting.nl [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 2IYnAH3XG3HX for ; Sun, 9 Nov 2008 16:55:33 +0100 (CET) Received: from ashley.powercraft.nl (84-245-3-195.dsl.cambrium.nl [84.245.3.195]) by node04.cambriumhosting.nl (Postfix) with ESMTP id 31DB4B0000BA for ; Sun, 9 Nov 2008 16:55:33 +0100 (CET) Received: from [192.168.1.213] (unknown [192.168.1.213]) by ashley.powercraft.nl (Postfix) with ESMTPSA id AD5CF23BC3D2 for ; Sun, 9 Nov 2008 15:20:34 +0100 (CET) In-Reply-To: <4915FCF8.9040703@powercraft.nl> 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 Jelle de Jong wrote: > Hello everybody, > > I have been testing several scenarios to find some glues why some usb > audio devices did not fully work and gave stuttering sounds I found the > following: > > usb devices define a max power attribute during there enumeration > process. I have some usb devices that have this at 500mA and some that > have this on 100mA. > > I also have some usb hubs that have external extra power supply and some > that are only a hub with bus power. > > Here it comes: > > Make sure the 4 port usb hub is full with for example: > - usb keyboard (100mA) > - usb mouse (100mA) > - usb audio (100mA or 500mA) > - usb stick (200mA/500mA) > > - usb hub with external power (500mA MaxPower) (AC adapter delivers 1A) > - usb hub without external power (100mA MaxPower) > > Make sure to use audio with several tones low tones (most dvds will do) > > When connecting a 100mA usb audio devices on a hub with external power > it will give stuttering sound!! (most usb audo devices are 100mA and > most hubs are external powered due to more then one usb stick) > > When connecting a 500mA usb audio device on a hub with external power it > will work perfectly. > > When connecting a 100mA or a 500mA usb audio device on a hub without > external power it will work perfectly. > > I have the idea there is something wrong with the power distribution > system when using external powered usb hubs... > > Any ideas how to correctly address this problem/bug? > > Best regards, > > Jelle > I did some more debugging, it think the 100mA/500mA behavior is just an effect of the real problem the usb isochronous audio bandwidth under Linux is doing some things that make usb audio not working very well. I wanted to be able to use 4 usb audio device on one usb at the same time. using a powered usb hub this gives shuttering sound. What are the max usb bandwidth limits on Linux? I also found out that the only what that all usb audio device work is to connected them directly without any hub between them. This takes up a lot of resources. Would somebody have to possibility to take a good look at the usb audio issues with multiple devices and isochronous transfers? Thank in advance, Jelle