From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Cussins Subject: Re: proposal: snd_pcm_start_at() Date: Tue, 07 Oct 2014 13:48:47 +0100 Message-ID: <5433E12F.70305@eml.cc> References: <1412260460.3891605.174362449.667FB9BE@webmail.messagingengine.com> <542D8E3F.4080400@linux.intel.com> <542E8FE4.4080904@eml.cc> <542F2216.7050801@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from out1-smtp.messagingengine.com (out1-smtp.messagingengine.com [66.111.4.25]) by alsa0.perex.cz (Postfix) with ESMTP id 68CAA26045E for ; Tue, 7 Oct 2014 14:48:59 +0200 (CEST) Received: from compute2.internal (compute2.nyi.internal [10.202.2.42]) by gateway2.nyi.internal (Postfix) with ESMTP id E657C2074B for ; Tue, 7 Oct 2014 08:48:58 -0400 (EDT) In-Reply-To: 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: Takashi Iwai , Pierre-Louis Bossart Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org Hi Takashi, On 06/10/14 10:45, Takashi Iwai wrote: > At Fri, 03 Oct 2014 17:24:22 -0500, > Pierre-Louis Bossart wrote: >> >> On 10/3/14, 7:00 AM, Tim Cussins wrote: >>> Hi Peirre, >>> >>> The pcm hardware for the new platform can start rendering when a compare >>> register matches a hw counter (driven by the audio clock). This allows >>> for starting with frame-accurate timing. >> >> Interesting. I wonder if you actually need a new extension for this, you >> could write the timestamp in an ALSA control and implement your .trigger >> function by using the contents of the control, i.e. delay the actual >> start. it wouldn't be generic but your hardware isn't either. > > Well, your suggestion sounds really tricky. The trigger is supposed > to trigger the stream immediately, and the delay isn't considered > there in principle. The system can work with delays, but it's not in > a form of the initial design. > > I think some synchronized triggering mechanism is missing in API, too. > There has been a similar request from others in the past (Digigram > wanted to have such a feature), so maybe it's not so uncommon > scenario. > > This would be a good topic to be discussed in the upcoming audio > mini-summit, but both of you won't be there, right? > I didn't have any plans to be at the mini-summit, but Glasgow isn't too far away... > > Takashi >