Re: Make a chirp signal with CoreAudio
Re: Make a chirp signal with CoreAudio
- Subject: Re: Make a chirp signal with CoreAudio
- From: Brian Willoughby <email@hidden>
- Date: Tue, 21 Apr 2009 15:38:23 -0700
On Apr 21, 2009, at 14:39, malcom wrote:
I should need to make a chirp (linear) signal out my speaker as like
in http://en.wikipedia.org/wiki/Chirp.
Is it possible with CA?
Anyone can point me to the right way to make it using CoreAudio?
CoreAudio places no limitations on the types of signals that you can
process. You basically hand off any digital audio signal data, and
CoreAudio will allow playback, provided that the hardware interface
is capable of the frequencies.
Your question is a matter of creating the signal, and thus has little
to do with CoreAudio. You could obtain a sound file containing a
chirp from any available source, and play it on your system. For
example, the Wikipedia entry you cite has two sound files which will
play in CoreAudio via your browser. If you cannot find an existing
file that meets your needs, then you need to create the digital audio
samples yourself, which is done independently of CoreAudio.
Because this is synthesis, you might find it useful to create an
AudioUnit Music Instrument, but CoreAudio only defines the mechanism
for passing along the digital audio. It's always up to you to create
the content or obtain it from elsewhere.
To put it another way, if you were to write a program which could
play the files from that Wikipedia page, then that would be the sum
total of your CoreAudio API usage. Any additional code that you
write to generate digital signal data would not be using CoreAudio.
For help with the latter, you could seek out general tutorials on
digital signal processing.
Brian Willoughby
Sound Consulting
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