Extracting pitch information from sound files
mark at maseurope.net
Fri Mar 7 07:31:39 EST 2008
On 7 Mar 2008, at 09:37, David Glasgow wrote:
> 1/ How hard would it be to parse sound files recorded in Rev and
> extract just the chunks of data relating to pitch ?
The way sound is digitally recorded does not have chunks relating to
pitch specifically. An audio file is essentially a long list of
numbers that describe the changing amplitude of the waveform of sound
- this theoretically encompasses all the properties of sound - pitch,
timbre and timing.
> 2/ Does it make any difference if the sound is complex (like an
> animal call) or simple like a signal from a tone generator?
Yes. The simpler the sound the easier it will be.
> 3/ Are any of the formats offered by Rev easier to handle in this
The difference between uncompressed sound file formats (.wav
and .aiff for instance) is really only in the file headers - the
audio data itself is generally the same.
> 4/ Assuming standard bit rates, how much pitch data would be
> generated by, say a ten second recording?
Typically, uncompressed sound files store a certain number of samples
per second per channel. The CD standard is 44100 samples per second,
with each sample being a two-byte signed integer (the sample size).
So ten seconds from a stereo CD would be 10 * 44100 * 2 * 2 = 3528000
> 5/ I have settled for post hoc parsing rather than 'on the fly'
> processing because I assumed the overhead would be too great for
> the latter to work. Is that right?
> 5/ Are there any other sensible questions I should be asking?
I'd probably start looking for any command-line tools that you could
call from Rev. Maybe google 'pitch extraction', 'audio analysis' as a
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