From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: [alsa-devel] [PATCH v2] staging: bcm2835-audio: interpolate audio delay Date: Mon, 05 Nov 2018 17:11:47 +0100 Message-ID: References: <20181022191708.GA4659@ubuntu> <046aea96-e0d3-60f4-c61a-c26bb1b5c193@gmail.com> <9884c4f5-2343-e3a4-8d8b-dd2db404ef27@gmail.com> <126FA055-050B-4AAC-9392-CA8CCA821768@eircom.net> Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Mike Brady Cc: Stefan Wahren , devel@driverdev.osuosl.org, alsa-devel@alsa-project.org, f.fainelli@gmail.com, julia.lawall@lip6.fr, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, eric@anholt.net, linux-rpi-kernel@lists.infradead.org, nishka.dasgupta_ug18@ashoka.edu.in, Kirill Marinushkin , linux-arm-kernel@lists.infradead.org List-Id: alsa-devel@alsa-project.org On Mon, 05 Nov 2018 16:57:07 +0100, Mike Brady wrote: > > > One another thing I'd like to point out is that the value given in the > > patch is nothing but an estimated position, optimistically calculated > > via the system timer. Mike and I had already discussion in another > > thread, and another possible option would be to provide the proper > > timestamp-vs-hwptr pair, instead of updating the timestamp always at > > the status read. > > Agreed — that would give the caller the information needed to do the > interpolation for themselves if desired. And now I wonder whether the problem is still present with the latest code. There was a (kind of) regression in this regard when we introduced the fine-grained hardware timestamping, but it should have been addressed by the commit 20e3f985bb875fea4f86b04eba4b6cc29bfd6b71 ALSA: pcm: update tstamp only if audio_tstamp changed Could you double-check whether the tstamp field gets still updated even if no hwptr (and delay) is changed? thanks, Takashi