From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lennart Poettering Subject: Re: [patch][saa7134] do not change mute state for capturing audio Date: Tue, 19 Jul 2011 14:25:33 +0200 Message-ID: <20110719122533.GD8224@tango.0pointer.de> References: <4E19D2F7.6060803@list.ru> <4E1E05AC.2070002@infradead.org> <4E1E0A1D.6000604@list.ru> <4E1E1571.6010400@infradead.org> <4E1E8108.3060305@list.ru> <4E1F9A25.1020208@infradead.org> <4E22AF12.4020600@list.ru> <4E22CCC0.8030803@infradead.org> <4E24BEB8.4060501@redhat.com> <4E2524DF.7070502@list.ru> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from tango.0pointer.de (tango.0pointer.de [85.214.72.216]) by alsa0.perex.cz (Postfix) with ESMTP id 07C2C2459B for ; Tue, 19 Jul 2011 14:26:28 +0200 (CEST) Content-Disposition: inline In-Reply-To: <4E2524DF.7070502@list.ru> 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: Stas Sergeev Cc: ALSA devel , "Nickolay V. Shmyrev" , linux-media@vger.kernel.org, Devin Heitmueller , Mauro Carvalho Chehab List-Id: alsa-devel@alsa-project.org On Tue, 19.07.11 10:31, Stas Sergeev (stsp@list.ru) wrote: > 2. "Even if it sucks in general". In this case, what solution > would you propose to get the problem of the white > noise fixed? Well, for removing the probing in PA we'd need a way to reliably figure out in which combinations of input and output we can open a sound card. i.e. we want to know if we can run surround 5.1 output and spdif output at the same time, or surround 5.1 output and stereo input and so on. And we'd need a lot of other attrbites about the sound card, and all that without having to open any PCM device. But that would be really hard to do, the current format neagotiation in ALSA PCM works very differently. And that's the reason why so far nobody has bothered with getting this right. The current code in PA to figure this out is somewhat ugly. It's slow, since we open the card in a lot of different combinations to test what works. It's fragile, since if somebody else has opened the soundcard we get an EBUSY which we take as hint that a specific combination didn't work, and so on. It's a hard problem, Lennart -- Lennart Poettering - Red Hat, Inc.