From mboxrd@z Thu Jan 1 00:00:00 1970 From: Clemens Ladisch Subject: Re: snd-usb-audio syncronisation problem Date: Fri, 22 Feb 2008 14:09:14 +0100 Message-ID: <47BEC97A.3030507@ladisch.de> References: <43e8c7320802220151p177d2c73y2c9724a4cb4743ef@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from out3.smtp.messagingengine.com (out3.smtp.messagingengine.com [66.111.4.27]) by alsa0.perex.cz (Postfix) with ESMTP id 6AC32245D0 for ; Fri, 22 Feb 2008 14:07:28 +0100 (CET) In-Reply-To: <43e8c7320802220151p177d2c73y2c9724a4cb4743ef@mail.gmail.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: Adrian Stancu Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org Adrian Stancu wrote: > I'm using an E-MU 0404 USB interface with the snd-usb-audio module > from alsa 1.0.16, operating in isochronous asynchronous mode. This > interface was producing very annoying click/pop sounds at regular > intervals during playback. Eventually I discovered that the > syncronisation mechanism telling the driver to send audio data faster > or slower to match the interface's consumption speed does not work as > expected, for some reason. The momentary frequency as requested by the device is shown in /proc/asound/card?/stream? (if CONFIG_SND_VERBOSE_PROCFS is enabled). Try something like: while sleep 0.3; do grep "Momentary freq" /proc/asound/card0/stream0; done In theory, once the device has determined its own speed relative to the computer, this value should be nearly constant. (When a stream has just been started, the requested frequency usually is higher because the device's buffer is empty.) Regards, Clemens