Reaper's Spectrograms

[LuCsa]

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

[cfillion]

There is https://www.reaper.fm/sdk/reapeaks.txt but it looks outdated (v5.15+ uses floating point, and it doesn't mention spectrograms & spectral peaks)...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.

[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).

[mschnell]

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).

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

[Philbo King]

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

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.

[LuCsa]

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.

[dave_t]

Taking the hijack further,

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

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

[bezusheist]

SoX can be used to generate spectrograms.