On Fri, 2 May 2014 17:48:37 -0700
Ricky Huang <[email protected]> wrote:

> Hello all,
> 
> I am trying to reproduce the Shazam algorithm as outlined in Avery Wang's 
> paper "An Industrial-Strength Audio Search Algorithm" 
> (http://www.ee.columbia.edu/~dpwe/papers/Wang03-shazam.pdf).  One of the step 
> in this is to convert the audio to spectrogram and identify the spectrogram 
> peaks.  I am wondering if building a custom audio-filter for ffmpeg would be 
> the correct way to go?  If so, does anyone have any pointers on converting 
> the audio data to spectrogram for me?  (algorithm to use, things to note, 
> etc?)
> 
> 
> Any help would be appreciated.  Thanks.

No idea about the algorithm, but if you want to see a sample filter how
to integrate such a filter into libavfilter, have a look at
libavfilter/avf_showspectrum.c. This filter visualizes the computed data.

If you actually want to export the filtered data instead of visualizing
it audio-player style, you could do something like vf_cropdetect.c, and
attach the filtered data to output AVFrames.

(If you just want to convert the data, my reply is probably not helpful
at all.)
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