Simple Audio question

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2 total messages Started by Joseph Peck Fri, 14 Dec 1990 17:10

#7463

Author: Joseph Peck
Date: Fri, 14 Dec 1990 17:10

25 lines
1269 bytes

Hello all.  I have a quick question on how to correctly select an 
audio channel for playing a sound.

Currently everything works; i.e. I allocate all 4 channels, and can 
play a sound on any given channel.  However, I get warnings when I
compile my program with lattice C.  I select the channel with:

AIOptr->ioa_Request.io_Unit = #;

where # is either 1,2,3 or 4.

I am assuming that I should be putting something other than just simple
constants here, but the RKM's don't cover this too well. (I am sure that
someone will probably disagree with me, but I really don't see it)

The better part is that the RKM's refer to io_Unit as a bit field, while
the header files seem to think that it is a pointer to a structure.
Maybe I am just too tired to read it correctly.....

So, can anyone give me a hand?

Thanks,
Joe Peck
peck@ral.rpi.edu

Re: Simple Audio question

#7547

Author: Ken Farinsky - CATS
Date: Mon, 17 Dec 1990 18:52

40 lines
1864 bytes

In article <8GG^X6$@rpi.edu> peck@ral.rpi.edu (Joseph Peck) writes:
>
>...how to correctly select an audio channel for playing a sound.
>
>I get warnings when I compile my program...I select the channel with:
>
>AIOptr->ioa_Request.io_Unit = #;  /* where # is either 1,2,3 or 4. */
>
>Joe Peck peck@ral.rpi.edu

I'm not the audio expert, but I'll try to answer your questions.
Looking through the RKM (Libs&Devs) in the Audio Device section, I found:

p610:  You specify the channel that you want to use by setting the
appropriate bits in the ioa_Request.io_Unit field...

from p615, it looks like the bits are set up as follows:

	CHANNEL_0	(1<<0)
	CHANNEL_1	(1<<1)
	CHANNEL_2	(1<<2)
	CHANNEL_3	(1<<3)

Also, from page 614:  If the allocation succeeds, the audio device
will return the channels that you now own in the lower four bits
of the ioa_Request.io_Unit field...So I would guess that you don't
use numbers like 1,2,3 or 4.

So, even though the field is a pointer, you have to put bit values into
it.  Try something like:

	AIOptr->ioa_Request.io_Unit = (struct Unit *)(CHANNEL_0);

Also, remember to mask out any unused bits when checking the value of
this variable and to set unused bits to zero when setting this variable.
-- 
--
Ken Farinsky - CATS - (215) 431-9421 - Commodore Business Machines
uucp: ken@cbmvax.commodore.com   or  ...{uunet,rutgers}!cbmvax!ken
bix:  kfarinsky

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