#spectralpainter

I’ve replaced the code that was generating the images you saw, with the functions I’ve extracted. Now I keep a float matrix and don’t work converting the initial spectrogram image. Having a single line on, it has no difference.

I’ve noticed that without the image normalization the recomputed spectrogram would look like the original, but with normalization it has black values on the line, so probably they are negative values, I’m not sure there can be negative values though.

The recomputed signal has frequency that seems double of the original from the inverse STFT.

TODOs:

In the inverse STFT I should use the window I used for the STFT.

The way I manage the time shift is wrong.

So, I hope you are not superstitious... :D

I’ve added multiplication by a Hamming window. It’s applied in the STFT from bottom left to bottom right.

I’ve made some progress on the STFT and iSTFT implementation. I had some sleepy-coding dumb bugs, even on the debug visualization. I still have to check if the STFT is correct. You can see the iSTFT of the top image below it, and it’s STFT at its right.

Thanks to Howard Antares, from the JUCE forum, I’ve found the terrible bug that was haunting me.

https://forum.juce.com/t/image-pixels-y-problem/43088/11?u=thegiallo

It was an uninitialized variable due to shadowing. I’m used to have all the warnings possible turned on, but in JUCE I didn’t think about setting them, so the compiler was silent and my mind continued to switch between the meanings of the `h` variable. It was both hue and height, at the same time, depending on the place. So strange.

So now I have this correct hue-saturation plot. Hurray!

I was curious about the pattern that was being created by the uninitialization, and in theory the variable would have the value it had the previous iteration, because of the stack. I tried to initialize it manually to that value and the pattern was still there! I’ve made a shadertoy so that the whole world can benefit from my sleepy coding beautiful discovery.

https://www.shadertoy.com/view/wsGfRy

I’ve now added the flags, but there it comes... no warning. I’ve used goldbolt.org to investigate the problem and discovered that `-flto` disables the warnings about uninitialized use. Also Fahien noticed that the variable pointed by the arrow should be the uninitialized variable and not the assigned one.

https://godbolt.org/z/qnd5xh

So... in these two days I’ve achieved... nothing. I did notice that the HSV image was wrong, no y changes. So I’ve investigated, and confirmed problems on y. I’ve tried many things with no result. As last resort I’ve asked on the JUCE forums. I’m really tempted to go back to my opengl code with hotreload and no portability and raw audio management. https://forum.juce.com/t/image-pixels-y-problem/43088