C++/VB - crazy noise in Directsound

Asked By Ji

24-Mar-08 05:57 AM

I'm using Directsound to play two wavs.  Sound 1 is a looped wav and is run
with the looped flag set in Play().  Sound 2 is a sound that lasts about a
second and isn't looped.  Sound 1 turns off asynchronously via a button
control (using Stop()).  The next occurrance of sound 1 after sound 2 is
turned off has a loud unwanted pop that happens at the beginning of it.

I've tried everything I can think of and have started shooting in the dark.
Set the play position in the buffers to zero when turning sound 1 off,
polling sound 1 and waiting to turn it off until it's at a place I know is a
zero crossing.  I even tried releasing all the buffers and then
reinitializing everything after turning sound 1 off, but still get the pop
that goes along with the next occurrance of sound 2.  How to fix?  At least
one demo I've seen of how to use Directsound also has a similar problem.

24-Mar-08 04:12 PM

You may want to post this question here as well:

microsoft.public.win32.programmer.directx.audio

Mark

--
Mark Salsbery
Microsoft MVP - Visual C++

24-Mar-08 10:19 PM

Even in ordinary playing, I've heard an odd "pop" now and again as the sound card is
activated.  Have you tried it on another machine to see if there is something related to
this phenomenon that may be driver-related?
joe


Joseph M. Newcomer [MVP]
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25-Mar-08 12:31 AM

Hi Joe, hope all is well.

I've tried it on two pretty dissimilar machines.  HP/98/Soundblaster vs
laptop/newish/Dell.

Incidently the pop is at the beginning of sound 2, not as I typo'ed below.

It seems to becaused by looping.  If I run sound 1 unlooped, then no problem
at the beginning of sound 2.  If I run sound 1 looped, but stop it at the
same place it stops when running unlooped, then I get the problem.  If I stop
sound 1 at random places,  I get the problem as well of course.

25-Mar-08 10:31 AM

I'll see if I can replicate this in the non-DirectSound world, but it will take me a while
to get the program installed on my desktop (it seemed to do this on my old desktop while
looping, but doesn't do it on my laptop).  I'll see what I can find out.
joe


Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm

25-Mar-08 12:24 PM

A pop occurs when a high magnitude sample is started playing.  It seems in
your case there is some stale data from the first sample still in the
playback buffer that is popping.

I believe when you start playback, Windows normally starts the playback at
volume 0 and quickly ramps it up so that whatever you are playing does not
pop.  It seems in your case this is not happening; playback starts at full
volume and pops.

You may want to flush the DirectSound device or open/close it as necessary.
I use the wave API's and that's what I do.  I've not used DirectSound too
much.

-- David

26-Mar-08 02:00 AM

Keeping a loop of silence running, at the suggestion of Chris P., has solved
the problem. This is apparently a Directsound bug.  Thanks, all.

Jim