From: Jag Talon <jag@aangat.lahat.computer>
Subject: Re: emulators/minivmac: add sndio for sound
To: George Koehler <kernigh@gmail.com>, Alexandre Ratchov <alex@caoua.org>
Cc: ports@openbsd.org
Date: Tue, 23 Jul 2024 17:35:21 -0400

Thank you gkoehler! It's so nice to see audio working on OpenBSD.

On Tue, 2024-07-23 at 17:17 -0400, George Koehler wrote:
> I committed my sndio diff together with Jag's README diff.
> 
> On Tue, 23 Jul 2024 11:24:46 +0200
> Alexandre Ratchov <alex@caoua.org> wrote:
> 
> > For non-blocking writes to work, the caller must call poll(2) or an
> > equivalent to wake up when the device can accept data. I couldn't
> > find
> > any poll(2) calls in the ALSA backend so I don't understand how
> > writes
> > are triggered. Does it retry periodically? If so, you need to call
> > sio_pollfd(), poll(), sio_revents() before the non-blocking
> > sio_write().
> 
> The write trigger is MySound_EndWrite0 in OSGLUXWN.c, which returns
> true when the emulator has filled 1 buffer (with kOneBuffLen
> samples).
> The ALSA backend might do a partial write, leave the leftover samples
> in the ring of 16 buffers, wait for the next trigger, then try to
> write the leftover sound plus the new buffer.
> 
> When I tried the non-blocking sio_write, the leftover samples seemed
> to grow longer than the ring ("sound buffer over flow" in
> OSGLUXWN.c).
> I heard 3 seconds of audio, because it stopped calling sio_write
> after
> 3 seconds.  I did use sio_pollfd, poll, sio_revents; but might have
> made some other mistake.
> 
> I switched to the blocking sio_write because I didn't want the
> leftover samples to grow.
> 
> On Tue, 23 Jul 2024 07:53:14 -0400
> Jag Talon <jag@aangat.lahat.computer> wrote:
> 
> > Ok to add the following diff to the README to remove the note about
> > missing audio?
> 
> I forgot to update the README.  Thank you for doing it.
> --gkoehler
> 

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