On 9/7/06, Charles Henry czhenry@gmail.com wrote:
On 9/5/06, Chuckk Hubbard badmuthahubbard@gmail.com wrote:
Just a thought... the output of a recursive filter from an input of an impulse would be several impulses of linearly changing amplitude at equally spaced intervals, and it would seem like that ought to give some sort of sawtooth if you put it through IFFT.
I tried to do this, like you said, but couldn't figure it out. I tried to use z~ with a throw~ and catch~ on very small blocksizes, but I couldn't get the throw/catch to work. same with send~/recieve~
then, I ran the output to ifft~ on overlapping blocks and windowed with the hanning window
Let me know if you get it working
Chuck
I was thinking something like this. I was wrong, it's exponential decay, not linear, so it wouldn't create a sawtooth exactly. I also can't for the life of me figure out why the impulse response moves every time I hit bang on here. It seems like it should always start right at the left side of the graph, but sometimes it doesn't show up, and other times it skips around in the graph. But if you set coefficients for the filter, bang until something shows in the response, and set the volume, it does make a harmonic sound.
-Chuckk
Actually, you inspired a different idea from me...Not a solution...but something I thought would sound weird. without exponential decay...the impulse response of a simple recursive filter that repeats itself every 3 samples, for example, would look like 1,0,0,1,0,0,... then, 0,1,0,0,1,0,... on the next block then, 0,0,1,0,0,1,... on the 3rd block
If these were in successive overlapping windowed blocks, it would be a sound that rotates through all the frequencies (in the fourier basis) over 3 blocks... but it requires that we have a feedback from every 3 samples, and to experiment, it would be good to be able to vary the number of samples in feedback
Now if you want to create a sawtooth, you have to compute the fourier series to see the coefficients. and phase is important. the sawtooth function is odd, so it's entirely a sine series. To get the phase correct, you have to feed all your frequencies to the imaginary input of ifft~
Chuck
On 9/7/06, Chuckk Hubbard badmuthahubbard@gmail.com wrote:
On 9/7/06, Charles Henry czhenry@gmail.com wrote:
On 9/5/06, Chuckk Hubbard badmuthahubbard@gmail.com wrote:
Just a thought... the output of a recursive filter from an input of an impulse would be several impulses of linearly changing amplitude at equally spaced intervals, and it would seem like that ought to give some sort of sawtooth if you put it through IFFT.
I tried to do this, like you said, but couldn't figure it out. I tried to use z~ with a throw~ and catch~ on very small blocksizes, but I couldn't get the throw/catch to work. same with send~/recieve~
then, I ran the output to ifft~ on overlapping blocks and windowed with the hanning window
Let me know if you get it working
Chuck
I was thinking something like this. I was wrong, it's exponential decay, not linear, so it wouldn't create a sawtooth exactly. I also can't for the life of me figure out why the impulse response moves every time I hit bang on here. It seems like it should always start right at the left side of the graph, but sometimes it doesn't show up, and other times it skips around in the graph. But if you set coefficients for the filter, bang until something shows in the response, and set the volume, it does make a harmonic sound.
-Chuckk
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Charles Henry -
Chuckk Hubbard