From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raymond Yau Subject: Re: safe support for rewind in ALSA Date: Tue, 23 Feb 2010 10:44:22 +0800 Message-ID: <4f3252891002221844o46844423x92b275d36640b127@mail.gmail.com> References: <6160a5131002010920j4417a34ai9f410fb500f7f305@mail.gmail.com> <4f3252891002081459q29f02414hf168a596ab641995@mail.gmail.com> <4f3252891002100519h132fddb8t1f2bc56e97bf5c40@mail.gmail.com> <4B72B665.3060903@ladisch.de> <4f3252891002102252vb6d7a94l76fb78e33da37775@mail.gmail.com> <4B73AFD5.4080205@ladisch.de> <4f3252891002141903q34144f58n60978e28e65640b4@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pw0-f51.google.com (mail-pw0-f51.google.com [209.85.160.51]) by alsa0.perex.cz (Postfix) with ESMTP id DFA93244DA for ; Tue, 23 Feb 2010 03:44:23 +0100 (CET) Received: by pwi9 with SMTP id 9so2891675pwi.38 for ; Mon, 22 Feb 2010 18:44:22 -0800 (PST) In-Reply-To: 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 2010/2/21 Kai Vehmanen > Hi, > > > On Mon, 15 Feb 2010, Raymond Yau wrote: > > Even using a high resolution timer , the application still cannot achieve >> latency better than the configured period size >> >> For USB case , the driver cannot give accurate hw pointer position , hw >> pointer increase in steps for the current implementation, (i.e. the graph >> is >> > > ... but that's a real hardware limitation for the USB-driver, right? And > even in the USB case, hw pointer is incremented in steps of URB transfer > size, so even in this case, latency of a highres timer based application is > not limited by the set period-size. > > I guess alsa pulse plugin also has the same problem since the value returned by pointer callback of the pulse device is also not accurate