[Openal] Max number of sources (and legit id values) foreachOpenALimplementation

[Daniel PEACOCK]

Hi Jason,

I would interpret the parameters as "hints" when you are passing them in to
alcCreateContext - because you might not get what you are asking for.  When
you get the values back with alcGetIntegerv I would  expect them to reflect
actual available resources though.

e.g If I requested 1 stereo source, and get back 1 Stereo and 62 Monos (==
64 hardware voices), this would mean I could create 63 Sources and expect
to play 1 stereo and 62 monos simultaneously.   Attempting to play 2
stereos and 61 monos on the 64 Sources would not be guaranteed to work (and
wouldn't on hardware).

If I needed two stereo sources - perhaps to do enable cross-fades of a
stereo music track - then I should request 2 stereos at context creation
time.   In the example above I would expect to get back 2 stereos and 60
monos - and be allowed to generate a maximum of 62 Sources.

Dan
Creative Labs (UK) Ltd.

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             Jason Daly                                                    
             <jdaly at ist.ucf.ed                                             
             u>                                                         To 
                                       Daniel PEACOCK                      
             07/23/2009 05:10          <dpeacock at creativelabs.com>         
             PM                                                         cc 
                                       Chris Robinson                      
                                       <chris.kcat at gmail.com>,             
                                       "openal at opensource.creative.com"    
                                       <openal at opensource.creative.com>    
                                                                   Subject 
                                       Re: [Openal] Max number of sources  
                                       (and legit id values)               
                                       foreachOpenALimplementation         
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Daniel PEACOCK wrote:


      Hi All,

      The original motivation for having the ALC_MONO_SOURCES and
      ALC_STEREO_SOURCES hints was due to the fact that an OpenAL Source
      that can be used to play buffers that could have anywhere between 1
      and 8 (maybe even more) channels of data. For software mixers this is
      no big deal - but for hardware devices that require one voice per
      channel (e.g Stereo requires 2 voices) it is a big problem. If you
      are running on a hardware device with 128 voices then generating 128
      sources and using them to play 128 mono buffers is OK - but you can't
      use them to play 128 Stereo buffers.



Yeah, I understand that.  The only thing I wasn't clear on was what you get
back when you call alcGetIntegerv with ALC_MONO_SOURCES or
ALC_STEREO_SOURCES.  The spec calls these "hints", so it's not really clear
on what you will get back (unless I'm missing something again).

If I were writing an implementation, I could argue that you should only get
your hint values back, but it sounds like the intent is that it should
return the number of sources actually available.

--"J"
ForwardSourceID:NT0006E15E