Re: Calibrating Buffer Size and Count

On Sun, 2010-05-30 at 13:09 -0700, Chris Robinson wrote: 
> On Sunday, May 30, 2010 12:39:40 pm Kip Warner wrote:
> > For audio effects, probably 48 KHz files will be used. For music, they
> > may end up being 96 KHz / 24-bit.
> 
> FWIW, I'd imagine most games use 44.1khz, or possibly 48khz, for music, and 
> either 22khz or 44.1khz for sound effects (16-bit for each). There's nothing 
> really wrong with using more, though, as long as you're okay with the 
> increased memory use.
> 
> Also be aware that OpenAL doesn't support 24-bit samples. They would need to 
> be converted on load to 32-bit float for use with the AL_EXT_FLOAT32 
> extension, or else convert to 16-bit.
> 
> > Do you recommend having the sole
> > configurable aspect being the total length of the entire buffer queue
> > for a source? That way a user can select 500 ms, 1s, 2s, etc. for their
> > machine and it can automatically calculate the size of each buffer
> > required, given the number of hard coded buffers, bit rate, frequency,
> > channels, etc..
> 
> I'd recommend that any hard-coded buffer size be specified using sample 
> frames, so it can increase with higher-resolution samples (eg. multiply by 2 
> for 16-bit mono, and 8 for 32-bit float stereo). But beyond that, increasing 
> the number of buffers for higher sample rates should be fine. eg:
> 
> BufferBytes = 16384 * (channels*bitspersample/8);
> BufferCount = max(4*samplerate/44100, 2);
> 
> So that rates above 44.1khz will use more buffers to keep from running out too 
> fast (and rates below will use less, but you'll need at least two regardless).
> 
> > Very helpful and thank you. You're very knowledgeable and this is
> > helping greatly as I finish up the audio component of the engine design
> > for my game (https://www.avaneya.com). Actually, when the design is
> > done, it would be really helpful if you were able to take a moment and
> > look at just the AudioManager's UML.
> 
> You're welcome. And I can take a look at it when it's done, sure. :)
> 

Thanks a lot for your help!
-- 
Kip Warner -- Software Engineer
OpenPGP encrypted/signed mail preferred
http://www.thevertigo.com

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