Re: Iterating through audio data
Re: Iterating through audio data
- Subject: Re: Iterating through audio data
- From: Brian Willoughby <email@hidden>
- Date: Wed, 25 May 2011 21:08:01 -0700
Duh, sorry for the mistype. That message should read: "441 Hz
sampling rate for a file with 44,100 Hz data" if you want 100:1
instead of merely 10:1.
If you want to plot every 100 samples, then set up an ExtAudioFile
class object with an AudioConverter that gives you a 4,410 Hz
sampling rate for a file with 44,100 Hz data. This will
efficiently thin out the data for you, and then your task will be
much simpler. You could also reduce the bit depth to 16-bit or
less, assuming the input file is 24-bit. On second thought, you
may run into difficulties attempting to break from the canonical 32-
bit float, but perhaps it's worth an attempt. At the very least,
the sample rate reduction will help even if you keep the canonical
bit depth.
Brian Willoughby
Sound Consulting
On May 25, 2011, at 19:58, GW Rodriguez wrote:
Yes I assumed that I wasn't going to plot each sample. My plan was to
start with every 100 samples and see how it looks.
So here's what I'm looking at doing:
// open audio file
// find length in samples of the file
-(void) getData {
AudioBufferList tempList;
for (SInt64 i=1; i < length; i = i+50) {
Err = ExtAudioFileSeek(audioFileRef, i);
UInt32 s = (UInt32) i;
Err = ExAudioFileRead(audioFileRef, &s, &tempList)
// something to print amplitude
}
}
So I'm not sure about the AudioBuffer and how to get the float
values (-1.-1.).
Thanks a bunch Brian
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