From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lars-Peter Clausen Subject: Re: [PATCH v4 6/8] ASoC: compress: Add support for DAI multicodec Date: Thu, 03 Jul 2014 20:23:16 +0200 Message-ID: <53B59F94.6040803@metafoo.de> References: <20140701164134.GH2296@intel.com> <53B400DE.3040205@baylibre.com> <20140703064147.GK2296@intel.com> <53B539E8.1000301@baylibre.com> <53B53C6B.8020707@metafoo.de> <53B540EE.30009@baylibre.com> <53B541F0.1040105@metafoo.de> <53B5428F.9050100@baylibre.com> <20140703120613.GP2296@intel.com> <20140703121846.GB410@sirena.org.uk> <20140703161517.GQ2296@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from smtp-out-175.synserver.de (smtp-out-175.synserver.de [212.40.185.175]) by alsa0.perex.cz (Postfix) with ESMTP id 20D59261A74 for ; Thu, 3 Jul 2014 20:24:25 +0200 (CEST) In-Reply-To: <20140703161517.GQ2296@intel.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: Vinod Koul Cc: alsa-devel@alsa-project.org, misael.lopez@ti.com, Mark Brown , lgirdwood@gmail.com, Benoit Cousson List-Id: alsa-devel@alsa-project.org On 07/03/2014 06:15 PM, Vinod Koul wrote: > On Thu, Jul 03, 2014 at 01:18:46PM +0100, Mark Brown wrote: >>> BUT Now thinking over this again, does this make sense do do with multiple >>> codecs?? >> >>> For folks haveing decoders in DSP inside SoC, the compressed device will be >>> actually a FE. The BE will be PCM to which codec would be linked. The folks >>> supporting decoders inside codec like WM wont ever need this. >> >>> Mark, do you agree to this? >> >>> So re-thinking again on why we need this?? >> >> The use case tends to be for applications that have one device per >> physical output. This isn't normally mobile, it's normally high >> performance audio applications where people are doing things to try to >> electrically isolate the analogue outputs or dealing with high power so >> need to keep speaker outputs physically separate. I can imagine set top >> box type applications (which do use offloaded media decode) doing this. > > Not sure if I follow you, I have no idea of how these systems work. > > But if sound card has compressed device it would need to represent using DPCM as > we don't know the decoder PCM output. The multiple codecs would then connect to > the PCM BE. > So on Compressed FE, we wont have multiple codecs. > > For codecs, the compressed audio will go to one codec, multiple ones wont make > sense. > > So how can we have a situation where we have compressed device linked to > multiple codecs? > If the assumption is that a DAI link that has a compressed DAI on the CPU side is never connected to a 'real' CODEC (or multiple CODECS) on the CODEC side. I think we can just leave soc-compress.c alone and just add a sanity check to make sure that num_codecs is always 1. - Lars