For demonstration purposes, there is spectrogram function in
wavelets-spectrogram package, which can be loaded with asdf like
so: (asdf:load-system :cl-wavelets/examples). This function can
produce a spectrogram of an uncompressed wav file (it uses only the
first channel).
spectrogram(filename-wav filename-jpg &key (w 600) (h 800) (block-length *block-length*) (wavelet *wavelet*))Build a spectrogram for the first channel of an audio file in WAV
format with the name filename-wav. The spectrogram is written as a
jpeg image with the name filename-jpg. w and h parameters
define dimensions of the image.
The spectrogram is built using frequency-domain function with data
block of length block-length each constructed from the input data.
Wavelet wavelet is used in the PWT algorithm.
*wavelet*:cdf-4-2 works
very bad, do not use it. :cdf-2-2 is the best choice.*block-length*Here is some examples of histograms with decription (all of them are obtained using CDF-2-2 wavelet):
