# acid2

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1. ## Working with FFT Results.

Admiral, do not worry about sounding rude. I am VERY (about a week into this stuff) new to signal processing so it's true I don't have a strong grasp on this work. I do know what I'm trying to achieve, but maybe I'm approaching the problem from the wrong angle which is why I'm getting confused. I will have a play around with the ideas given here, probably on sunday and see what I get. Again, many thanks to everyone who has contributed despite my confused mumblings :)
2. ## Working with FFT Results.

TheAdmiral, yea, that's exactly it :) I'm assuming 0 < x < (pi) for these, so sin(x) is 1Hz. a) sin(100x)? 100hZ, ±5hZ b) sin(100x) + sin(200x)? 100hZ-150hZ, because the sin(200x) (that's the second harmonic right) will not vary the frequency, but will create a more square wave c) sin(100x) + 2*sin(200x)? Not sure on this one... but I'm again thinking 100hZ-150hZ, probably more at 150hZ, but I can't visualise this waveform as well. d) Whitenoise, constrained between 100 and 200Hz? If it is truely uniform, 150Hz e) Whitenoise, constrained (by the PCM format) between 1 and 44.8kHz? I guess 22.4kHz, again as long as the noise is uniform. f) Silence? Hmmm, hadn't considered this. I suppose 0hz in this case, but you don't really get full silence in EDM. If possible, I'd like to make the statistical operation ignore absolute amplitude (comparing relative instead). I will be colouring amplitude by varying the alpha value. Spurious_interrupt: Ahhh, I follow you now, that makes sense. How does FFT 'know' I have 44100 samples each second? Is it because it's constant between each sample, so the interval covers the same range in each 'chunk'? Also, as you said, the frequency changes are not linear, but I don't think that'll be too much of a problem. This is a very rough check, so I just need to check certain limits, that I'll find through quick experiments
3. ## Working with FFT Results.

Right, I did some reading into wavelet transforms, and yea - they are complex. One site summarised it nicely, that FTs give frequency information only, with no time information. I don't really need time information, so -should- be cool with just fourier transformations. In regards to the frequency content, here's my assumption. I store my data in an array, lets say of length 512. Then, I feed this array into my FFT function and it transforms each value. I just assumed because it's a transformation like this that it simply went up to 512hz. However, seeing as the data is sampled at 44khz, does that mean each value in my array is a step of 44000/512 ? Really appreciate your help so far spurious_interrupt, so I gave you a alovely R++ :)
4. ## Working with FFT Results.

Spurious_interupt, yea I figured that, but my fft library (exocortex for .NET) seems to create the frequency scale from the amount of samples you feed it. Ie, give it 500 samples, the maximum frequency is 500hz. And those short notes, are quite often the high ones... I'll have a look at that wavelet transform you speak of.
5. ## Working with FFT Results.

Thanks for the input spurious_interupt, but I know most of what you've told me (amplitude is defined by the modulus of the complex number). I think the Nyquist frequency is packed into the 0th element of the array. TheAdmiral, sorry to be unclear. What I'm trying to achive is the following. The user can load a wave form in, and I take chunks of this waveform, as I render it (say, 10000 samples) and analyze the frequency information, colouring the wave accordingly (like a thermometer, high is hot, mid is warm, bass is cold). As far as I know, FFT is the best of doing this. I understand it's probably not going to be as simple as that, because in real music you've got a LOT going on at once, but I'm curious to see how this works out. I think I want what you talk about with log-spectrum and such, but that was all too quick for me... Mind expanding on that? Thanks for the input so far all!
6. ## Working with FFT Results.

Well, I don't know Matlab (should learn that one day), but I am outputting my results into a CSV file, and using Excel to draw graphs. Here is my input: And here is the FFT output: Notice all the bunching in the bass frequencies... I want some type of numerical way to represent this bunching, if possible.
7. ## Working with FFT Results.

Hey all, I'm currently doing a little bit of DSP work (very new to it!) and am doing a small project that colorizes a waveform by frequency of discrete intervals. To do this I am using a FFT on my sample sets to create a frequency spectrum. The problem I now come to, is analysing this spetrum. I want a way to either pick out a specific peak average frequency, or the peak frequency band. Any ideas?
8. ## Platform game curved geometry editor

I wanted to chuck down my suggestions on splines - Catmull Rom and Hermite splines both seem to produce nice results. Game Programming Gems 5 has an article on Hermite splines for minimal turning acceleration, giving "sharp" curves.
9. ## Any good free fonts out there?

I think http://www.dafont.com/ is the best font resource I've found... you should find something good there.
10. ## Hottest girl from any game.

Quote:Original post by DogCity Close, you really mean: Yumness (Sniper Wolf, MGS)
11. ## Do you DJ? Want to join up with me and a friend on a small station?

Hey all, I've been talking with a friend who used to DJ a fair bit of trance music, and was showing him some of my bedroom dnb sets I've done - and he likes them. I also shoutcast to my friends and he tuned in once, and we talked about getting a station and such... The next day we had one :P It's just a small 12 man server - but with only me and him DJing it's not much good. Our main aim is to get a lot of different genres of music in - he does trance, I do drum and bass - maybe someone else could throw something else in? I just thought I'd shout out here - cause we're looking for some more people to dj with us :) If you wanna talk to me on MSN about it (which would be best) - I'm on at depth.of.field@gmail.com.
12. ## Lack Of Interest In Programing!!!

Hahaha, I seem to be a user of lib-boredom (with aimless staring of boredom trance), in fact, while writing this sentance I (ab)used stareAimlessAtWindow() :(
13. ## Some thoughts about renderers and deferred shading

Quote:Original post by Matt Aufderheide Sorry, this doesn't make sense. You can't do per-pixel point lights without shaders... You need to transform the light vector, vertex normal, vertex postions, etc to tangent space, and then calculate attenuation in a per pixel basis, normalize everything..do specualr, etc etc.. Sorry, but you cant do this on a GeForce 2, no matter what tricks you use. So the point is, comparing some kind of FFP dot3 lights with per pixel shader-based lights such as in this deferred shading debate is non-sensical.. they are differnt things entirely. Sorry, this doesn't make sense. As it's been said above, you CAN do per pixel normal mapping on this (ancient) hardware. The tangent (I think?) is encoding in vertex colouring and then the dot3 map is combined with a diffuse texture, the hardware handles the rest. If you don't believe me, explain how BltizBASIC does it, with no shader support whatsoever? Now while I agree it is not a fair comparison because the last deferred demo showed more than what zedzeek is on about, it's still true what zedzeek may be saying.
14. ## How (if at all) are you planning?

Hey all, Was curious, how much time are you spending on planning? I understand a lot of you are going solo so maybe planning isn't as essential, but I was quite impressed to see a fair few people able to jump straight in. Me and Rim have spent a lot of time so far just jabbering on about ideas, conisdering whether xyz will work, etc. We're keeping all our notes in a small DokuWiki (which is a very nice system!) After that, we're (well, I am, anyway) thinking about making user story cards, then moving onto the coding. Hopefully start coding some time next week, I'd imagine. What about you?
15. ## 4E

WOOT! FSOL! Someone with some good taste in music ^_^