[Openal] Channels

[David Yazel]

Ack that shoots my design... back to the drawing board.  Looks like Sources are important resources to manage carefully.

Now about stereo not being hardware acellerated... what does that mean? I am concerned about cpu contention between rendering and sound.  I would have assumed that stereo was a preferred format for most sounds, but I don't want to lose lots of FPS in software sound synthesis.

On another note I am having some trouble getting distance attenuation to work.  I wonder if there are any newbie pitfalls which are common.  I have set the reference distance, rolloff factor, min gain, max gain, listener position-orientation-velocity and source position-orientation-velocity.  I move the sound from 0 to 30 units from the listener over time, but the sound does not decrease in volume. I was kinda pulling my hair out last night.  If I get more info I will post it.


>-----Original Message-----
>From: Daniel PEACOCK [mailto:dpeacock at creativelabs.com]
>Sent: Friday, September 12, 2003 04:41 PM
>To: 'David Yazel'
>Cc: openal at opensource.creative.com
>Subject: Re: [Openal] Channels
>
>
>
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>Hi David,
>
>> So the limit is on 1-sources (i.e. source names), 2-playing sources or 3-sources with buffers?
>
>There is a limit on the number of Sources that can be generated at once, because it is assumed that
>you may want to play all the sources simultaneously.  Conversely there is no limit (or at least a
>very high limit) on the number of Buffers you can create.
>
>However, you are right that it is possible that in some implementations if you choose to use a
>source to playback a multi-channel buffer (currently only stereo supported) it could take up
>additional resources.
>
>If you know that you need to play back 2 stereo sources, you could generate 2 sources, attach stereo
>buffers to them, and then try and generate as many 3D buffers as you.
>
>FYI ... On the Windows openal32.dll "wrapper", using the "DirectSound3D" device to get hardware
>acceleration, hardware voices are only used for 3D mono sources.  Stereo sources are played using
>software - so that actually don't take any voices from the hardware.  They will still take 1 Source
>to play though.
>
>Dan
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>                      "David Yazel"                                                                                                            
>                      <david at yazel.net>                To:       <openal at opensource.creative.com>                                              
>                      Sent by:                         cc:                                                                                     
>                      openal-admin at opensource.c        Subject:  Re: [Openal] Channels                                                         
>                      reative.com                                                                                                              
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>                      09/12/03 04:33 AM                                                                                                        
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>So the limit is on 1-sources (i.e. source names), 2-playing sources or 3-sources with buffers?  I
>would have assumed you could have as many sources as you would want, but should limit the number of
>those which play at one time.  Also, is there a second limit in the number of hardware channels
>being used?  So for example would 5 sources each playing a 2 channel stereo buffer use 10 total
>channels?  I am not sure how I could enumerate the number of channels by "trying" it without knowing
>in advance what buffers each source would be using.
>
>David Yazel
>http://www.magicosm.net
>http://xith3d.dev.java.net/
>"No matter how complicated it looks, in the end it is just a bunch of triangles"
> ----- Original Message -----
> From: Garin Hiebert
> To: David Yazel ; openal at opensource.creative.com
> Sent: Friday, September 12, 2003 1:31 AM
> Subject: Re: [Openal] Channels
>
> There isn't a way to ask how many sources are going to be available.  A
> common way to figure it out is to generate them one at a time when the
> program launches until it fails.
>
> It is quite common for a product to want to play more sounds than there
> are sources available, in which case you have to come up with some kind
> of voice management scheme to allocate the available resources.  A
> common approach is to assign priorities to each sound when it is played
> and only really play it if there is a source available, if there is a
> lower-priority sound that can be bumped, or if there is an older
> same-priority sound which can be bumped.
>
> Garin
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