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I am using windows audio core api to do loopback-capture and then processing the data. On my machine I get 48000 sampling rate with 32 bit floats for the format. Is that what Windows is using internally? I'm wondering if I'm tapping the output before any hardware specific conversion so the format is always the same, or if I might be getting 16 bit ints on some other machine?

Rick Saada
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There is clearly some variation between machines, at least with respect to sample rate, as WASAPI on my machine gives 32-bit floats at 44100Hz. The documentation for GetMixFormat (remarks section, paragraphs 2 and 3) suggests that the supplied format is the internal format used for mixing, and that it may well differ from what the sound card actually accepts as input, but doesn't make clear exactly which formats may be used. I suspect that this is intentionally vague so as to encourage developers to handle multiple formats in the case that they may be used somewhere. That said, given they are abstracting the mix format from the sound card, I would be surprised if they used different internal formats on different machines.

TheSuccessor
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  • I expect that they use float internally to avoid quantization from scaling, possibly converting to ints on the output if the soundcard requires it. But matching the sampling frequency the sound card wants seems likely. Thanks for the info. – Rick Saada Mar 30 '16 at 00:49