Path: utzoo!attcan!uunet!cs.utexas.edu!usc!apple!Apple.COM!lsr
From: lsr@Apple.COM (Larry Rosenstein)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Playing sounds async: help
Message-ID: <2587@internal.Apple.COM>
Date: 30 Jun 89 00:23:31 GMT
References: <7975@bsu-cs.bsu.edu>
Sender: usenet@Apple.COM
Organization: Objects-R-Us,  Apple Computer, Inc.
Lines: 36

In article <7975@bsu-cs.bsu.edu> mithomas@bsu-cs.bsu.edu (Michael Thomas 
Niehaus) writes:

> 1.  Why am I not supposed to leave an open sound channel for a period of
>     time?

I think that when you create a sound channel, you get control of the sound 
hardware, which prevents anyone else from making a sound.  (According to 
the System 7.0 preliminary docs, this is supposed to be fixed.)

> 2.  Right now, I am allocating a new channel, then doing the SndPlay.  I
>     sound is done, and if it is then dispose the channel.  But how can I
>     find out if it is finished?

You need to put a call back command in the channel after you play the 
sound, and specify a call back routine when you create the channel.  Your 
call back routine will get called when the sound finishes.

Other things to watch out for. 

You can't reuse the sound channel, because once you play a snd resource 
with it, the channel gets linked with a synthesizer.

You must lock the snd handle if you are playing it asynchronously  SndPlay 
will lock it for the duration of the call only, which will be shorter than 
the duration of the sound (if you are using async sound).

Finally,  you can look at the sample unit that I wrote, which should be on 
Info-Mac.  (It also appeared recently on comp.sources.mac.)  It was 
written in Pascal and shows how to do all these things.

Larry Rosenstein, Apple Computer, Inc.
Object Specialist

Internet: lsr@Apple.com   UUCP: {nsc, sun}!apple!lsr
AppleLink: Rosenstein1