Re: Apparent sndio issue with underruns on OpenBSD?

From: Mike Brady <>
Date: Mon, 24 Feb 2020 09:19:33 +0000
Thanks for the quick response. I’ll move to a real machine and report back. The original fault report came from a user on a real machine, but of course using a VM will complicate matters – I should have thought of that!


> On 24 Feb 2020, at 07:00, Alexandre Ratchov <> wrote:
> On Sun, Feb 23, 2020 at 11:17:15AM +0000, Mike Brady wrote:
>> Hi there. I'm the principal developer of Shairport Sync, an Apple
>> AirPlay 1 "server" -- a program that accepts audio from a "client"
>> such as iTunes and directs it to an audio output. It runs on OpenBSD
>> and FreeBSD using the sndio system using a "backend" that takes
>> commands and audio from Shairport Sync and directs them to the sndio
>> subsystem. (It also runs on Linux using ALSA and others).
>> I am writing because while Shairport Sync works well on FreeBSD it
>> is crashing on OpenBSD (please see
>> I'm testing
>> on an installation of OpenBSD 6.6 in a VMWare Fusion VM on an
>> iMac. AFAIK all the software is up to date with patches, etc. The
>> installation procedure I'm following is at
> Thanks, I'll look more in depth in the github discussion.
> I don't know what audio device VMware emulates (probably eap), but
> there were many reports about broken audio in virtual machines. It
> seems that there are subtle play/rec synchronization differences
> between the real hardware and the emulated one which tend to break
> sndiod.
> If you don't care about recording, you could try to run the sndiod of
> the OpenBSD VM with the '-m play' option and see if problems are gone.
> For instance, run as root:
> 	rcctl set sndiod flags -m play
> 	rcctl restart sndiod
> Another option would be to use a remote soundcard instead of the one
> of the OpenBSD VM. For instance, add the '-L -' sndiod option to the
> working system, then run the client on the OpenBSD system with the
> following environment variable set:
> 	AUDIODEVICE=snd_at_<ip_addr>/0
> where <ip_addr> is the IP address of the working system. This way you
> could test on OpenBSD without using the emulated hardware.
> Let me know if this works.
>> If I start shairport-sync and play a track from, say, the Music app
>> on the iMac, everything is fine until I switch tracks. It seems
>> (this is me guessing) that underruns occur and that they cause the
>> sndio system to stop responding for about four seconds and then
>> enter an error state, returning an error code of 1 for
>> everything. When I changed the xrun behaviour to SIO_ERROR the
>> program would immediately terminate on those occasions. I wonder if
>> you might be able to offer any suggestions.
> This happens when there's a hardware anomaly detected, here when the
> driver doesn't process an audio block for more than 4 seconds. When
> this occurs, sndiod closes the device and disconnects all clients,
> hence the errors in the programs.
> HTH,
> -- Alexandre
Received on Mon Feb 24 2020 - 10:19:33 CET

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