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Date:   Mon, 05 Nov 2018 17:11:47 +0100
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From:   Takashi Iwai <tiwai@suse.de>
To:     Mike Brady <mikebrady@eircom.net>
Cc:     Stefan Wahren <stefan.wahren@i2se.com>, devel@driverdev.osuosl.org,
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        linux-rpi-kernel@lists.infradead.org,
        nishka.dasgupta_ug18@ashoka.edu.in,
        Kirill Marinushkin <k.marinushkin@gmail.com>,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [alsa-devel] [PATCH v2] staging: bcm2835-audio: interpolate audio delay
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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