Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030248AbVKPJLY (ORCPT ); Wed, 16 Nov 2005 04:11:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030251AbVKPJLY (ORCPT ); Wed, 16 Nov 2005 04:11:24 -0500 Received: from webmailv3.ispgateway.de ([80.67.16.113]:22246 "EHLO webmailv3.ispgateway.de") by vger.kernel.org with ESMTP id S1030248AbVKPJLW (ORCPT ); Wed, 16 Nov 2005 04:11:22 -0500 Message-ID: <1132132269.437af7ad5f8c4@www.domainfactory-webmail.de> Date: Wed, 16 Nov 2005 10:11:09 +0100 From: Clemens Ladisch To: Markus Rechberger Cc: linux-kernel@vger.kernel.org Subject: Re: snd_usb_audio References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT User-Agent: Internet Messaging Program (IMP) 3.2.8 X-Originating-IP: 213.238.46.206 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1494 Lines: 47 Markus Rechberger wrote: > finally the em28xx driver made it into the kerneltree, but one > problem still remains > the snd_usb_audio driver. > > The problem with the snd_usb_audio driver is that it only supports > up to 10 isochronous packets. This is packets per URB; we typically have 8 URBs. > If people watch TV using such a framegrabber device and set audio > to > 8000hz the video isoc transfer will break and the video will > stop. What exactly breaks? Are you using playback or capture? If there is an underrun when starting a _playback_ stream, then it's a known bug that has been fixed in 2.6.15-rc1. > regarding usbaudio.c (in 2.6.14): > #define MAX_PACKS 10 > #define MAX_PACKS_HS (MAX_PACKS * 8) /* in high speed mode */ > > MAX_PACKS is the upper limit that is adjustable, the second one > isn't used at all > > an easy hack would be to allow up to 100 packets but I also have a > usb 1.1 soundblaster that might have problems with too many packets. > > The correct value for em28xx devices is around 80 packets. Did you test this? Capturing doesn't use MAX_PACKS. > does anyone know more about the packet limitations on USB 1.1 and > 2.0 devices? The only limitation are the host controller drivers. HTH Clemens - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/