asBands actually returning the bacnds like low frequencies, mdeium
frquencies and stuff.
I believe you need asFrequencies() which will split the whole interval
0-11KHz into equal chunks and calc the power of the desired audio chunk in a
particular range.
See doc for example:
http://pymedia.org//docs/pymedia.audio.sound.html#SpectrAnalyzer
For now the smallest frequency range you can get via asFrequencies() is
44000/ ( 4* 512 )= 22Hz
Dmitry/
----- Original Message -----
From: "Robert Helmer" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Sunday, January 08, 2006 12:27 AM
Subject: Re: [Pymedia-users] pitch detection
Hi Dmitry,
Thank you for your reply! I have been trying out the asBands() method,
which seems to yield some result to different voice tones. However, it
seems that asBands() can only return a limited set of possible
frequencies.. I am basically doing this :
snd= sound.Input( RATE, CHANNELS, sound.AFMT_S16_LE )
snd.start()
analyzer= sound.SpectrAnalyzer( CHANNELS, SAMPLES, NUM_FREQS )
while 1:
largestFreqName= 0
largestFreqValue= 0
previousLargestFreqValue= 0
bands= analyzer.asBands( BANDS, snd.getData() )
for i in range( 0, len( bands ) ):
for j in range( 0, len( bands[i] ) ):
freqName= bands[i][j][0]
if freqName >= 1000:
continue
freqValue= bands[i][j][1]
if freqValue > largestFreqValue:
previousLargestFreqValue= largestFreqValue
largestFreqName= freqName
largestFreqValue= freqValue
print largestFreqValue
Am I understanding how this data may be used correctly? Is there some way
to do something similar with the analyzer.asFrequencies() method? I cannot
seem to make any sense out of the returned data through experimentation :)
Thanks!
Rob Helmer
Dmitry Borisov wrote:
Hi,
It could work for you.
Basically SpectrAnalyzer is taking the fixed number of samples >512 and
returns the frequencies strength. If you use much more samples it may not
work well for you though.
Sorry I never did pitch detection myself, so I cannot tell if it'll work
for you.
Dmitry/
----- Original Message ----- From: "Robert Helmer"
<[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, January 03, 2006 12:25 PM
Subject: [Pymedia-users] pitch detection
Hello,
I am working on a voice-training python application that involves pitch
detection. I have had some good results using FFT but it's a bit too
slow (I can't get good detection without a very large sample size it
seems).
Could SpectrAnalyzer be useful for pitch detection? I am a bit confused
as to how to use this class properly; the example (sound_viz.py) doesn't
work in the latest release due to what looks like API changes. I think
being able to experiment with a working implementation would help me to
be able to play around with FFT and other algorithms (Schmitt-triggering
for instance).
I took a peek at the implementation of SpectrAnalyzer in C and I am not
sure how much overlap there is between what I am trying to do and
SpectrAnalyzer; it seems quite capable but my inexperience in digital
audio processing is holding back my understanding.
I've been learning just how little I know about DSP by embarking on
this, so any suggestions would be greatly appreciated!
Thanks,
Rob Helmer
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