On Tuesday, August 10, 2010 6:42:18 AM UTC+12, Vladimir Vassilevsky wrote:
> John David Eriksen wrote:
> 
> > On Aug 9, 6:29 am, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
> > 
> >>John David Eriksen wrote:
> >>
> >>>When I'm done analyzing a chunk of sound, I want the following
> >>>information. I want the average amplitude of the energy at the given
> >>>frequency bands over the length of the sound sample expressed as a
> >>>floating-point value between 0 and 1.0:
> >>>I'm looking for something quick and dirty that can execute quickly.
> >>
> >>Use a simplest zero crossing period counter.
> >>Make a hystogram of half-periods.
> >>
> > Thanks for your help. Correct me if I am wrong, but doesn't zero
> > crossing information fail to give me any information about amplitude?
> 
> FWIW, the relation of the different columns in the histogram gives you 
> the relative estimate of energies at the corresponding frequencies.
> 
> 
> Vladimir Vassilevsky
> DSP and Mixed Signal Design Consultant
> http://www.abvolt.com

Zero crossing are an awful way to get information. Bit of noise and you're screwed.  In fact unless you have a very high SNR forget it.

On Sunday, August 8, 2010 7:46:47 PM UTC-7, John David Eriksen wrote:
> Hi All,
> 
> I'm working on a fun little audio side-project. I want to be able to
> create a sound collage using sounds I find online. I hope you can
> point me in the right direction with regard to algorithms, approaches,
> etc.
> 
> I'll be writing a Clojure (Java) program to find and download mp3s,
> chop them up into chunks, perform spectrum analysis on the chunks, and
> then write an algorithm to layer them together in such a way that I
> don't combine two or more chunks with lots of amplitude in a given
> frequency band. Basically, I want to avoid layering two very bassy
> sounds together or two very hissy sounds together so that the finished
> sound collage has some space and musicality. I'll want to figure out a
> quick way to adjust amplitude to prevent clipping, as well. But that
> will wait until a later time.
> 
> So. I've found Java libraries for manipulating chunks of sound, but
> have not found libraries that I could easily use to obtain the kinds
> of spectral information I want.
> 
> When I'm done analyzing a chunk of sound, I want the following
> information. I want the average amplitude of the energy at the given
> frequency bands over the length of the sound sample expressed as a
> floating-point value between 0 and 1.0:
> 
> 0 - 150
> 150 - 250
> 250 - 350
> 350 - 500
> 500 - 750
> 750 - 1000
> 1000 - 1500
> 1500 - 2500
> 2500 - 5000
> 5000+
> 
> A chunk of a bass-heavy dance track might look like: {0.8, 0.9. 0.6,
> 0.5, 0.4, 0.4, 0.3, 0.2, 0.2, 0.2}
> 
> A field recording of birds might look like: {0.0, 0.1, 0.2, 0.3, 0.5,
> 0.6, 0.4, 0.2, 0.1, 0.1}
> 
> I'm looking for something quick and dirty that can execute quickly.
> I've read enough about spectrum analysis to determine that I need to
> use an FFT. I located the following FFT Java library:
> http://sites.google.com/site/piotrwendykier/software/jtransforms which
> provides access to FFTs of various types over sets of single and
> double-precision data. I have a basic (if rusty) understanding of
> discrete math and have to admit that the Wikipedia pages on these
> subjects have not been terribly illuminating.
> 
> I appreciate any pointers and general guidance.
> 
> Thanks!
> 
> John David

Hi John, 
I was looking for something similar to find the rhythm and timbre of a song. Did you find any existing code or FFT libraries ( in java)  that would do this?

Thanks,
Mita

On Aug 9, 5:29=A0am, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
> John David Eriksen wrote:
> > When I'm done analyzing a chunk of sound, I want the following
> > information. I want the average amplitude of the energy at the given
> > frequency bands over the length of the sound sample expressed as a
> > floating-point value between 0 and 1.0:
> > I'm looking for something quick and dirty that can execute quickly.
>
> Use a simplest zero crossing period counter.
> Make a hystogram of half-periods.

Yet another option similar to this is to create a histogram
of the times between local maxima/minima inflection points;
or a 2D histogram using both time and delta amplitude
between these local extrema points.


--
rhn A.T nicholson d.0.t C-o-M
 http://www.nicholson.com/rhn/dsp.html

On Aug 9, 10:49=A0am, jacko <jackokr...@gmail.com> wrote:
> high pass the top half of your spectrum and measure the range min,max.
> square your residual and repeat for an octave division... normalize
> outputs to approximate unit range.
>
> Not as quick as Vlad's but will be different.
>
> Cheers Jacko

Hey Jacko,

Thanks for your suggestion. Much of your terminology is unfamiliar --
it looks like I have quite a bit to learn. I have access to FFT
libraries, but it looks like I have to perform operations on my data
once I have it in the frequency domain that may not be supported by
available Java libraries.

It looks like I'm either going to have to hit the books or keep
searching around for well-documented and ready-made software packages
that can help me out.

Thanks again,

John David

John David Eriksen wrote:

> On Aug 9, 6:29 am, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
> 
>>John David Eriksen wrote:
>>
>>>When I'm done analyzing a chunk of sound, I want the following
>>>information. I want the average amplitude of the energy at the given
>>>frequency bands over the length of the sound sample expressed as a
>>>floating-point value between 0 and 1.0:
>>>I'm looking for something quick and dirty that can execute quickly.
>>
>>Use a simplest zero crossing period counter.
>>Make a hystogram of half-periods.
>>
> Thanks for your help. Correct me if I am wrong, but doesn't zero
> crossing information fail to give me any information about amplitude?

FWIW, the relation of the different columns in the histogram gives you 
the relative estimate of energies at the corresponding frequencies.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

On Aug 9, 6:29&#4294967295;am, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
> John David Eriksen wrote:
> > When I'm done analyzing a chunk of sound, I want the following
> > information. I want the average amplitude of the energy at the given
> > frequency bands over the length of the sound sample expressed as a
> > floating-point value between 0 and 1.0:
> > I'm looking for something quick and dirty that can execute quickly.
>
> Use a simplest zero crossing period counter.
> Make a hystogram of half-periods.
>
> Vladimir Vassilevsky
> DSP and Mixed Signal Design Consultanthttp://www.abvolt.com

Hi Vladimir,

Thanks for your help. Correct me if I am wrong, but doesn't zero
crossing information fail to give me any information about amplitude?

John David

>
> When I'm done analyzing a chunk of sound, I want the following
> information. I want the average amplitude of the energy at the given
> frequency bands over the length of the sound sample

The MP3 compression has already perfomred a frequency domain analysis,
perhaps you can use the MP3 data?

Mark

high pass the top half of your spectrum and measure the range min,max.
square your residual and repeat for an octave division... normalize
outputs to approximate unit range.

Not as quick as Vlad's but will be different.

Cheers Jacko

John David Eriksen wrote:


> When I'm done analyzing a chunk of sound, I want the following
> information. I want the average amplitude of the energy at the given
> frequency bands over the length of the sound sample expressed as a
> floating-point value between 0 and 1.0:
> I'm looking for something quick and dirty that can execute quickly.

Use a simplest zero crossing period counter.
Make a hystogram of half-periods.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

Hi All,

I'm working on a fun little audio side-project. I want to be able to
create a sound collage using sounds I find online. I hope you can
point me in the right direction with regard to algorithms, approaches,
etc.

I'll be writing a Clojure (Java) program to find and download mp3s,
chop them up into chunks, perform spectrum analysis on the chunks, and
then write an algorithm to layer them together in such a way that I
don't combine two or more chunks with lots of amplitude in a given
frequency band. Basically, I want to avoid layering two very bassy
sounds together or two very hissy sounds together so that the finished
sound collage has some space and musicality. I'll want to figure out a
quick way to adjust amplitude to prevent clipping, as well. But that
will wait until a later time.

So. I've found Java libraries for manipulating chunks of sound, but
have not found libraries that I could easily use to obtain the kinds
of spectral information I want.

When I'm done analyzing a chunk of sound, I want the following
information. I want the average amplitude of the energy at the given
frequency bands over the length of the sound sample expressed as a
floating-point value between 0 and 1.0:

0 - 150
150 - 250
250 - 350
350 - 500
500 - 750
750 - 1000
1000 - 1500
1500 - 2500
2500 - 5000
5000+

A chunk of a bass-heavy dance track might look like: {0.8, 0.9. 0.6,
0.5, 0.4, 0.4, 0.3, 0.2, 0.2, 0.2}

A field recording of birds might look like: {0.0, 0.1, 0.2, 0.3, 0.5,
0.6, 0.4, 0.2, 0.1, 0.1}

I'm looking for something quick and dirty that can execute quickly.
I've read enough about spectrum analysis to determine that I need to
use an FFT. I located the following FFT Java library:
http://sites.google.com/site/piotrwendykier/software/jtransforms which
provides access to FFTs of various types over sets of single and
double-precision data. I have a basic (if rusty) understanding of
discrete math and have to admit that the Wikipedia pages on these
subjects have not been terribly illuminating.

I appreciate any pointers and general guidance.

Thanks!

John David