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Date:	Thu, 5 Oct 2023 23:21:18 +0200
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Subject:	Re: portaudio: only OSS host API available since version 19.20210406-2
To:	Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>, cygwin AT cygwin DOT com
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From:	Michael Panzlaff via Cygwin <cygwin AT cygwin DOT com>
Reply-To:	Michael Panzlaff <michael DOT panzlaff AT fau DOT de>
Sender:	"Cygwin" <cygwin-bounces+archive-cygwin=delorie DOT com AT cygwin DOT com>

Hi,

> In my environment, portaudio with MME support generates choppy sound
> for the suggestedOutputLatency of less that 60 ms. 70 ms seems to
> work. In this case, hostBufferCount=8 and hostBufferSizeFrams=480
> if the sample rate is 48 kHz. So, total buffer length is 3840 samples.
> Therefore, the resulted  latency is 80 ms.

interesting. I've now did some experiments with a self compiled 
portaudio with MME and WASAPI and both worked flawless on my machine 
with a suggestedLatency of 10ms. Perhaps this is dependend on the sound 
card used in the computer. The callbacks are called with framesPerBuffer 
of 480.

> OSS implementation in cygwin 3.4.9 always uses the buffer size of
> 125 ms. So, even if hostBufferCount=2 (current value of portaidio
> with OSS support), the latency is 250 ms. This might not be acceptable
> for some applications.

I wouldn't mind using OSS if it supports lower hostBufferSizes so that I 
don't get callbacks with a buffer size of 6000. Apparently 
suggestedLatency has no influence on that.
> Unfortunately, OSS and MME/DSound/WASAPI can be exclusively enabled.
> I am currently considering whether to rollback portaudio to MME/
> DSound/WASAPI until cygwin 3.5.0 is released.

I guess it would be possible but would probably require a patched 
configure script.

Either way if you change it away from OSS or now, I hope I could provide 
some useful feedback.

Best regards,
Michael

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