Re: sound cards and sampling rates (Malcolm Slaney )

Subject: Re: sound cards and sampling rates
From:    Malcolm Slaney  <malcolm(at)IEEE.ORG>
Date:    Fri, 4 May 2001 11:32:08 -0700

>If so, does anyone know how standard Apple sound cards deal with >non-standard sampling rates, or more generally, how to find out? Or >are there better sound cards that I should look into? Thanks! I'm pretty sure they interpolate, to whatever frequency is set for the input microphone sampling rate. I *think* the interpolation was done with a small-order polyphase implementation for rational sample rate changes, and then defaulted to linear interpolation. The nice thing was that you didn't have to worry about it, it just did the right thing. I haven't been at Apple for quite a few years, but that was my understanding when I was there (and part of the sound community). If you care, you should use Matlab to do the sample rate conversion. Then you know exactly what you have (and you probably want to play a chirp up to 20kHz to somebody young enough to still hear that high to make sure the sampling rate really is 44k and not 22k. :-) I believe the Apple sound hardware is above average in quality, that being one of Apple's prime markets, but they did expect people to use the digital output cards for the money-is-no-obstacle recording studios. They were using the Crystal 1-bit converters long before it was an important marketing buzzword. -- Malcolm

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