Re: Fwd: OpenAl Start/Stop crackle/pop
Re: Fwd: OpenAl Start/Stop crackle/pop
Hi Stefan,
I'm copying the coreaudio list because I also saw your post there.
On Wed, Jan 07, 2009 at 10:01:25PM -0800, Stefan Alder wrote:
> Marc, I saw your post here: http://opensource.creative.com/pipermail/
> openal-devel/2008-November/005315.html.
>
> Has this been resolved? I'm getting clicking on start and stop. Please let me
> know if you happen to have any ideas or if there's a patch out there that I can
> test.
>
> ---------- Forwarded message ----------
> From: Stefan Alder <email@hidden>
> Date: Wed, Jan 7, 2009 at 1:33 PM
> Subject: OpenAl Start/Stop crackle/pop
> To: email@hidden
>
>
> I'm using OpenAl to play a view different looping sounds. On calling
> alSourceStop, a crackle/pop sound is frequently produced. AlSourceStart then
> also produces a similar sound.
>
> 1) Stop crackle
> It seems that alSourceStop causes the sound to stop immediately, sometimes when
> the waveform amplitude is > 0, in turn causes the crackle. I can understand
> this, but I'm wondering if anyone can recommend a way to minimize this, i.e.
> perhaps stopping the sound when the waveform passes through 0?
>
> 2) Start crackle
> Before calling alSourceStart, the buffers are unqueued from the source, which
> as far as I can understand should clear the soure queue. But, it seems that
> some samples are left in the source's queue from the previous playback. Is
> there anyway to clear these?
>
> Thanks!
>
I recall that those ramp functions are only called for some of the
on/off functions. You might try ALSourcePause and ALSourcePlay and see
if it only happens on startup. If you follow the simple change to the
source--in my post that you've referenced--it should fix the problem.
If you are on the iphone, then you are SOL because you can't compile the
source :) I did submit a bug report to Apple on this issue. More
detail here: http://openradar.appspot.com/6388390
The better thing to do--which is what I'm doing now--is to stream the
audio and simply ramp up and ramp down the audio yourself. Look for a
recent AudioUnit example post of mine in the coreaudio mailing list.
Best,
Marc
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