Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262175AbVC2DmN (ORCPT ); Mon, 28 Mar 2005 22:42:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262172AbVC2DmM (ORCPT ); Mon, 28 Mar 2005 22:42:12 -0500 Received: from gate.crashing.org ([63.228.1.57]:41685 "EHLO gate.crashing.org") by vger.kernel.org with ESMTP id S262173AbVC2Dlo (ORCPT ); Mon, 28 Mar 2005 22:41:44 -0500 Subject: Re: Mac mini sound woes From: Benjamin Herrenschmidt To: Lee Revell Cc: Takashi Iwai , Linux Kernel list In-Reply-To: <1112067369.19014.24.camel@mindpipe> References: <1111966920.5409.27.camel@gaston> <1112067369.19014.24.camel@mindpipe> Content-Type: text/plain Date: Tue, 29 Mar 2005 13:41:02 +1000 Message-Id: <1112067662.12300.11.camel@gaston> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1641 Lines: 36 On Mon, 2005-03-28 at 22:36 -0500, Lee Revell wrote: > On Mon, 2005-03-28 at 09:42 +1000, Benjamin Herrenschmidt wrote: > > It seems that Apple's driver has an in-kernel framework for doing volume > > control, mixing, and other horrors right in the kernel, in temporary > > buffers, just before they get DMA'ed (gack !) > > > > I want to avoid something like that. How "friendly" would Alsa be to > > drivers that don't have any HW volume control capability ? Does typical > > userland libraries provide software processing volume control ? Do you > > suggest I just don't do any control ? Or should I implement a double > > buffer scheme with software gain as well in the kernel driver ? > > alsa-lib handles both mixing (dmix plugin) and volume control (softvol > plugin) in software for codecs like this that don't do it in hardware. > Since Windows does mixing and volume control in the kernel (ugh) it's > increasingly common to find devices that cannot do these. You don't > need to handle it in the driver at all. Yah, OS X does it in the kernel too lately ... at least Apple drivers are doing it, it's not a "common" lib. They also split treble/bass that way when you have an iSub plugged on USB and using the machine internal speakers for treble. > dmix has been around for a while but softvol plugin is very new, you > will need ALSA CVS or the upcoming 1.0.9 release. Ok. Ben. - 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/