From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Mack Subject: Re: caiaq driver: audio 4 dj and jackd Date: Mon, 02 Dec 2013 17:00:13 +0100 Message-ID: <529CAE8D.6020003@zonque.org> References: <529BF843.6000608@gmail.com> <20131202095948.GA2886@tamtam.fritz.box> <529CA3FC.1040301@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail.zonque.de (svenfoo.org [82.94.215.22]) by alsa0.perex.cz (Postfix) with ESMTP id 2955A261AB2 for ; Mon, 2 Dec 2013 17:00:16 +0100 (CET) In-Reply-To: <529CA3FC.1040301@gmail.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: "Gabriel M. Beddingfield" Cc: Alsa-devel , Antonio Ospite List-Id: alsa-devel@alsa-project.org On 12/02/2013 04:15 PM, Gabriel M. Beddingfield wrote: > On 12/02/2013 01:59 AM, Daniel Mack wrote: > Jack has always opened only one PCM device... which is the Right Thing > for most recording sound cards (e.g. ice1712, hammerfall, etc.). This is > the first "pro-sumer" device I've ever seen with multiple substream devices. I was also uncertain when I wrote the driver which way is better. But given that there are ways in ALSA to synchronously start separate streams, I eventually went the stereo pairs way. >> After all, the streams are guaranteed >> to be synchronous, as they share the same clock in hardware. > > TBH, the whole substream concept is lost on me. Where does this > guarantee come from? From the substream concept or from intimate > knowledge of this device? Both :) > (I.e. how would JACK know about the clock > guarantee?) snd_pcm_info_get_sync() should return the same clock id for both interfaces in that case. But I must admit I haven't tried this in awhile. >> Technically yes, but changing that would mean breakage for all other >> users, and making it configurable would result in yet another moving >> part which makes things even more complex. > > How would this cause breakage? Users that use 2 stereo substreams could > still work normally. Yes, unless you opened the first subdevice with more than 2 channels. Then an existing user for the second stream breaks. IOW: the possible configuration and usage for subdevice 1 changes depending on that of subdevice 0. > But, FULL ACK on the moving parts. That would indeed make the driver a > little gross on the inside. What are your results with the multi plugin? Is that something you can live with? Daniel