From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: 2 speakers are assigned to the same DAC, this can't support 4.0/2.1 channles Date: Fri, 12 Jun 2015 18:05:07 +0200 Message-ID: References: <5576B419.5010505@canonical.com> <5576E994.2080300@canonical.com> <5577BAEE.50506@canonical.com> <557A7718.5070100@canonical.com> 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 4A2132604AA for ; Fri, 12 Jun 2015 18:05:08 +0200 (CEST) In-Reply-To: <557A7718.5070100@canonical.com> 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: David Henningsson Cc: hwang4 , alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org At Fri, 12 Jun 2015 08:07:20 +0200, David Henningsson wrote: > > > > On 2015-06-11 17:10, Takashi Iwai wrote: > > At Wed, 10 Jun 2015 12:28:39 +0200, > > Takashi Iwai wrote: > >> OK, good to know. I'd like to test a bit more via hda-emu whether > >> this gives any ill effects. So far, this seems fixing a few other > >> machines, too, so it's a good thing to have in general. > > This change alone results in regressions on machines that are capable > > of 4.0/5.1 surrounds. For avoiding it, the badness for multi-io has > > to be increased as well. It's damn sensitive. > > > > But, now I wonder now whether blindly applying this is good. Suppose > > a machine with 2.1 speaker and one headphone, but the codec has only > > two DACs. With this setup, now the headphone and the speaker share > > the same DAC, as the cost of having individual 2.1 speaker volume. > > Is this more useful than having individual volumes for speaker and > > headphone? > > > > Maybe the machine you're trying to support has a different situation. > > So applying the new rule to limited devices is fine. But if so, it's > > not necessarily to be an adjustment of badness table, but just you can > > provide the simple DAC/pin preference map explicitly in the fixup. > > Oh, this is an interesting trade-off. > > In the PulseAudio desktop scenario, we automute the speaker, and > PulseAudio remembers the individual headphone and speaker volumes. So in > this case, there is no benefit from having individual headphone and > speaker volume at the ALSA level. > > However if a user wants to turn off automute, then there is a need for > being able to adjust headphone and speaker volume individually. > > But it's not just a question of volume control for 2.1. Being able to > send a different stream to the subwoofer could be useful too, especially > if the hardware filter is bad or non-existing. > > So my gut feeling leans towards using the second DAC for the subwoofer > speaker being the more useful default, but it's not a clear cut. Right, this is indeed a difficult problem, and probably there is never a clear answer. Another interesting examples are: A. 3 DACs, 2 HP, 2 speakers B. 3 DACs, 2 HP, 1 mic, 1 speaker C. 4 DACs, 2 HP, 1 mic, 2 speakers For B and C, user expects the possible 5.1 outputs by retasking the mic. But then you'll lose the individual volume control with the speaker. Takashi