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08-14-2018, 04:54 AM
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#1
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Human being with feelings
Join Date: Aug 2016
Posts: 87
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Reaper's Spectrograms
Hey, fellow Reapers.
I wondered how Reaper generates the spectrograms for its spectrogram view and if it's somehow possible/allowed to use Reaper('s spectrogram functionality) to generate spectrograms of a given wav file to use it outside of Reaper?
Also, is there a way to work with the peak data?
Thanks!
Lukas
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08-14-2018, 09:52 AM
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#2
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Human being with feelings
Join Date: May 2015
Location: Québec, Canada
Posts: 4,968
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There is https://www.reaper.fm/sdk/reapeaks.txt but it looks outdated (v5.15+ uses floating point, and it doesn't mention spectrograms & spectral peaks)...
EDIT: The API has GetMediaItemTake_Peaks which allow extracting spectral information.
Last edited by cfillion; 08-14-2018 at 11:37 AM.
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08-14-2018, 11:33 AM
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#3
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Human being with feelings
Join Date: May 2017
Posts: 3,204
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Not to hijack the thread, but it has often occurred to me that the spectral view, with a separate color per note, could be used to generate midi from audio (missing the octave).
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08-14-2018, 10:00 PM
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#4
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Human being with feelings
Join Date: Jun 2013
Location: Krefeld, Germany
Posts: 14,784
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Quote:
Originally Posted by Philbo King
Not to hijack the thread, but it has often occurred to me that the spectral view, with a separate color per note, could be used to generate midi from audio (missing the octave).
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I suppose the resolution is not fine enough.
Moreover this only would work for a sequence of pure sine waves, but not for real audio signals, containing multiple frequencies at the same time, so you can't easily "follow a melody" or even detect a chord.
To do this you would need to use e.g. Melodyne, that performs such things by really complex algorithms.
-Michael
Last edited by mschnell; 08-15-2018 at 06:51 AM.
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08-15-2018, 05:50 AM
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#5
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Human being with feelings
Join Date: May 2017
Posts: 3,204
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Quote:
Originally Posted by mschnell
I suppose the resolution is not fine enough.
Moreover this would only would work for a sequence of pure sine waves, but not for real audio signals, containing multiple frequencies at the same time, so you can't easily "follow a melody" or even detect a chord.
To do this you would need to use e.g. Melodyne, that performs such things by really complex algorithms.
-Michael
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I think you overstate your case a bit. I agree it's not great for chords, but I see definite consistent colors for any pitched mono melody, even with complex harmonics (pipe organ, distorted guitars, etc.). You do have a point that there is other software that would do the job better. But it would be a convenient feature.
Returning to the OP topic, I suppose there is better software for doing that as well. While you could drag a Wav into Reaper, turn on spectrograpgh peaks mide, and zoom it up to do a screen capture, the lack of frequency indicator lines and an amplitude color index would make it fairly useless for serious measurements. I suppose it depends on what you use it for.
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08-27-2018, 02:42 PM
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#6
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Human being with feelings
Join Date: Aug 2016
Posts: 87
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Hey guys, sorry for the very late reply!
As for the pitch detection idea: I side with Michael in that pitch detection is a very complex task for complex sounds (which almost any real sound is...) - I think we all agree on that - but yeah, maybe a simple algorithm would pick the frequency area of highest intensity (ignoring all other frequency contents), quantizing them to half-tone steps with respect to a given reference tone (e.g. 440Hz) --> extracting, so to say, the "monophonic melody of highest intensity". But even that could fail as for instance low piano notes tend to have a fundamental lower in intensity than its e.g. second partial.
But back to the topic: I asked because the spectrogram looks very convenient and simple, good enough in resolution. I have a recording where there are some clicks (one to two samples make a jag in the waveform). In order to find and correct them, I look for vertical sharp lines (meaning constant intensity over all frequencies at a given time) in the spectrum (the laws of Fourier analysis demand that a pulse in the time domain gives a constant frequency response). It would be so nice if Reaper could toggle into a "destructive wav editing" mode in order to make such corrections.
Cheers,
Lukas
@Reaper api... to be very frank...I don't understand the documentation of that function.
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08-31-2018, 07:09 AM
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#7
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Human being with feelings
Join Date: Jan 2016
Posts: 169
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Taking the hijack further,
Quote:
Originally Posted by mschnell
I suppose the resolution is not fine enough.
Moreover this only would work for a sequence of pure sine waves, but not for real audio signals, containing multiple frequencies at the same time, so you can't easily "follow a melody" or even detect a chord.
To do this you would need to use e.g. Melodyne, that performs such things by really complex algorithms.
-Michael
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There are a few plugins less "mainstream" than Melodyne that do audio to polyphonic MIDI - I assume they use spectral analysis. The results aren't pristine, but I think you could probably pick out melodies and hard-to-hear chords
e.g. https://www.kvraudio.com/product/mp3...y-nguyen-chung
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08-31-2018, 07:20 AM
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#8
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Human being with feelings
Join Date: Nov 2010
Location: Mullet
Posts: 829
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SoX can be used to generate spectrograms.
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