From mboxrd@z Thu Jan  1 00:00:00 1970
From: Clemens Ladisch <clemens@ladisch.de>
Subject: Re: Calculated average playback latency
Date: Tue, 14 Dec 2010 17:20:47 +0100
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References: <AANLkTikcrTA4hRp9AvOfZPGN0FrkKwYS3SaFq0W25NdE@mail.gmail.com>
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To: Jean-Yves Avenard <jyavenard@gmail.com>
Cc: alsa-devel@alsa-project.org
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Jean-Yves Avenard wrote:
> By default, Myth uses mmap access

Why?

> Problem, turned out his was using a USB audio device, and
> snd_pcm_hw_params_set_access didn't return any error.

USB audio devices do support mmap.

> ... I decided to stop using mmap and instead use snd_pcm_writei.
> 
> Now on my system, this has added quite a bit of latency and the A/V
> sync isn't perfect anymore...

Using mmap neither reduces latency, nor does it improve synchronization.

> Is there an official way to calculate an average system latency
> (doesn't need to be perfectly accurate).

Not the average, but try snd_pcm_delay().


Regards,
Clemens