Chromagram with logarithmic compression

[Jason T.]

Hi , I am now doing some works on key detection and I noted that logarithm on pitch then get the chromagram can make the performance better.

The pitch_to_chroma function in Matlab can implement this, so i wonder if there's method i can implement log compression before getting the chromagram by  

librosa.feature.chroma_stft 

the math function is Γ𝛾𝑥≔log(1+𝛾|𝑥|)  

Thanks!!

[Dan Ellis]

You can pass in a precomputed spectrogram to chroma_stft. So I think you want:

y, sr = librosa.load(wavfilename)
S = np.abs(librosa.stft(y))
chroma = librosa.feature.chroma_stft(S=np.log(1.0 + gain * S), sr=sr)

.. for some value of gain.

DAn.

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[Jason T.]

Thanks ! But as i implemented it , i got a weird chromagram (the second one )which seems lots different from the original one(the first one).

Then i tried to log the chroma(the third picture). I am wondering which method is more reasonable or similar to the Matlab function.

The following picture is a song in D minor.  Thanks !!

Dan Ellis於 2016年4月15日星期五 UTC+8下午9時29分35秒寫道：