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Date: Tue, 06 Dec 2022 02:24:38 +0100
From: qwx@sciops.net
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Subject: [9front] mixfs stutter
Reply-To: 9front@9front.org
Precedence: bulk

Hello,

There's been quite some work on streaming audio and improving mixfs
performance lately.  I've always had problems with mixfs, but unsure
what to do about them.  Important note: my main computer is still a
t61p, much slower than x220 and higher.  There are relatively frequent
stutters and underruns, esp.  when the system is under heavier load.
So far the best "fix" I found was to readjust buffer size and delay.
I'm not sure whether this fixes the underlying issue or just a symptom
though.  The patch below aligns NDELAY and NBUF to the default delay
(1764), and significantly improves performance, on intel hda at least,
on my machines.

What do you think?  Does this make sense?

Thanks,
qwx


diff 744053268d196e8c282d20243600fb33d4df0028 uncommitted
--- a/sys/src/cmd/audio/mixfs/mixfs.c
+++ b/sys/src/cmd/audio/mixfs/mixfs.c
@@ -5,10 +5,10 @@
 #include <9p.h>
 
 enum {
-	NBUF = 8*1024,
-	NDELAY = 2048,
 	NCHAN = 2,
 	FREQ = 44100,
+	NDELAY = FREQ / 25,
+	NBUF = NDELAY,
 };
 
 typedef struct Stream Stream;