From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: Logical device name for 4-channel microphones? Date: Tue, 24 Apr 2012 17:42:47 +0200 Message-ID: References: <1335011052.2268.18.camel@laptop> <4F96B3ED.3070007@ladisch.de> <1335281294.4604.19.camel@laptop> Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by alsa0.perex.cz (Postfix) with ESMTP id 961C524446 for ; Tue, 24 Apr 2012 17:42:47 +0200 (CEST) In-Reply-To: <1335281294.4604.19.camel@laptop> 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: Tanu Kaskinen Cc: alsa-devel@alsa-project.org, Clemens Ladisch List-Id: alsa-devel@alsa-project.org At Tue, 24 Apr 2012 18:28:14 +0300, Tanu Kaskinen wrote: > > On Tue, 2012-04-24 at 16:09 +0200, Takashi Iwai wrote: > > At Tue, 24 Apr 2012 16:08:45 +0200, > > Clemens Ladisch wrote: > > > > > > Tanu Kaskinen wrote: > > > > My problem is that I'd like to make Pulseaudio handle 4-channel webcam > > > > microphones[2], but I'm not aware of any input device names for > > > > 4-channel devices. Are there such device names? > > > > > > These device name are useful only for device types that are generic > > > enough. Four-channel microphones aren't. > > > > Hm, we have already surround51 or such specific one, so it's not too > > bad to have a definition for multi-channel mics. OTOH, surround51 & > > co were the possible cause of confusions, as there are way too many > > surround types. A generic type with the channels argument might be > > more generic? > > > > In anyway, I think it's fine to define some new generic name. > > From Pulseaudio point of view using "hw" should be fine if you can > guarantee that any current or future 4-channel mics can be opened in the > 4-channel mode using the "hw:CARD" device name. Such a thing can be never guaranteed with "hw" :) The hw provides nothing but what kernel driver provides. And the hardware might be a link of two stereo streams. Takashi > I'm just worried that > there might be cards that split the four channels to e.g. two stereo > devices, "hw:CARD,0" and "hw:CARD,1", and then "hw:CARD" won't work. I > might be mistaken, but aren't there some such cases with playback, which > have to be opened with the "surround" device names to get all the > channels? > > The "surround" devices also guarantee some specific channel mapping, > which may not match what "hw" uses, which is another reason to prefer > "surround" over "hw", but I don't think this applies to input side. > Therefore, the only possible problem that I can see with "hw" is that it > might not provide all channels. > > -- > Tanu >