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extAudioFile data... am I getting the right stuff?

Answer 1

A:

I think i've figured this out. I just graphed those points above in excel and it seems to look like a waveform. I didn't realize it was giving the negative voltages as well... but it makes sense.

Corey 2010-09-10 23:53:54

Answer 2

A:

this is normal.

the common floating point representation of audio samples modulate from [-1...1]; where the values -1 and 1 represent one sample at 0 dBFS.

a continuous stream of floating point values '0.0' represents a silent signal.

a signal with no DC offset will have equal weight in the positive and negative domains.

if you'd like to convert these values to [0...1], use the formula:

result = (0.5 * inputSample) + 0.5;

but you may have to use a more sophisticated algorithm if the signal extends beyond [-1...1].

in most cases, you should keep it at [-1...1] if you want to store it in floating point.

Justin 2010-09-11 06:04:45

Depending on how the audio was converted to float, the sample range may not be [-1, 1]. Specifically, on OS X floating point audio is typically (although not always) in the range [-1, 1). For example, using Apple's AudioConverter, for 16 bit audio the minimum sample -32768 is converted to -1 but the maximum sample 32767 is converted to (32767/32768) ≈ 0.999969

sbooth 2010-09-13 06:07:59

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extAudioFile data... am I getting the right stuff?

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