From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Mack Subject: Re: [Alsa-user] Ticks when playing to USB DAC at high sample rates Date: Wed, 07 Nov 2012 10:01:14 +0100 Message-ID: <509A235A.7000004@gmail.com> References: <3884466.olklcBH31l@quintet> <3608072.60TCDCLhjU@quintet> <509855FA.7000409@gmail.com> <9872736.seOqKZ7sS2@quintet> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wi0-f169.google.com (mail-wi0-f169.google.com [209.85.212.169]) by alsa0.perex.cz (Postfix) with ESMTP id 2741B265301 for ; Wed, 7 Nov 2012 10:01:22 +0100 (CET) Received: by mail-wi0-f169.google.com with SMTP id hq4so4539006wib.2 for ; Wed, 07 Nov 2012 01:01:20 -0800 (PST) In-Reply-To: <9872736.seOqKZ7sS2@quintet> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Jeffrey Barish Cc: alsa-user@lists.sourceforge.net, alsa-devel List-Id: alsa-devel@alsa-project.org On 07.11.2012 00:54, Jeffrey Barish wrote: > I guess that snd_usb_pcm_prepare is called by the core usb system to prepare > the snd driver. Anyway, snd_usb_pcm_prepare calls configure_endpoint with a > substream. Then configure_endpoint calls snd_usb_endpoint_set_params with the > data endpoint that corresponds to the substream. snd_usb_endpoint_set_params > calls data_ep_set_params with the data ep and data_ep_set_params sets nurbs to > 2 for the data endpoint. > > snd_usb_endpoint_set_params has code to call sync_ep_set_params when the > endpoint is type sync. sync_ep_set_params sets nurbs to 4 (why?). However, > snd_usb_endpoint_set_params never invokes the call to sync_ep_set_params > because ep->type is always data. Back up: snd_usb_endpoint_set_params is > called from configure_endpoint. It is called from an if block contingent on > the substream's having a sync endpoint. It does. However, the call to > snd_usb_endpoint_set_params passes subs->data_endpoint as the first argument, > so snd_usb_endpoint_set_params simply repeats the operations it performed as a > result of the previous invocation. I presume that the first argument to the > second call to snd_usb_endpoint_set_params should be subs->sync_endpoint. Eh. You clearly spotted a bug here. The rally interesting thing is that that it didn't bite us earlier, as it's in since 3.6. > I > made that change. Now freqm does change. However, I am getting tons of > ticks. Now it sounds as if the payload size is always wrong. > > Oh, 44.1 kHz works. 48 kHz works. 88.2 and 96 don't work. That's a different issue. Would you like to prepare a patch for the issue above please? Thanks, Daniel