Re: [Audacity-nyquist] eq-band and "width"
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From: James S. <www...@gm...> - 2010-10-25 19:55:53
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I guess I'm not understanding this version of octaves. Simple physic has a string cut in half is an octave up, doubled in length is an octave down. My interpretation translated to Hz is Hz/2 = down an octave and Hz*2 = up an octave. I'm using 1.2 for pseudo octaves for more bands. What would be the formula for width in this case? (sqrt (mult 1.2 1.2)) ? Isn't that 1.2? Or is it more complex? Ultimately I'll use a loop, just keeping it simple to get the jist of it for now. aka Semi-Human readable. On 10/25/10, Roger Dannenberg <rb...@cs...> wrote: > On 10/25/10 12:40 PM, James Shatto wrote: >> Based on the band being frequency/width to frequency*width, that >> really simplified what I was trying to do. For 22-ish bands the width >> would be 1.2-ish. Which places the 22nd band up past sampling rates >> of 48kHz, so I don't know if that will be problematic for samples at >> or less than 48kHz. Most of my samples are in the 192kHz / 96kHz >> realm, so not a problem for me (at the moment). >> >> I'll probably want to expand it later to allow a variable width and >> therefor variable bands. And I'm still not entirely sure if it does >> exactly what I want. But it does seem to work. And with most of the >> desired effect. In some respects better than expected, but I've still >> got to run the results through the ringer. i.e. downsample the long >> way to maximize clarity. >> >> http://home.earthlink.net/~shadow_7/FauxFurEQ.ny > I took a look here: it looks like your width parameter is 1.2, but bands > go from freq/1.2 to freq*1.2. Your bandwidth is 1.44, but you need to > specify this in octaves. A ratio of 1.44 is 0.526069 octaves, so the > width parameter to eq-band should be 0.526069. That's if you want the > filter response to be gain/2 at freq/1.2 and freq*1.2. You could > increase or decrease width to get more or less overlap. > > There's no need to write out equations for each band -- you could use a > loop to simplify the code (or maybe that would "complexify" it by adding > control constructs and data structures). The nband-range function uses a > loops-and-array approach to do something similar. > > -Roger >> Feel free to set me straight if my logic is based on misunderstanding. >> It wouldn't be the first time. >> >> - James >> >> >> On 10/25/10, Roger Dannenberg<rb...@cs...> wrote: >>> On 10/25/10 5:49 AM, James Shatto wrote: >>>>> How would you specify the spline? >>>> linearly it would be (current frequency)/(max frequency)*(dB >>>> adjustment) = (dB adjustment) >>>> >>>> my current math is more like (current gain for frequency) = (previous >>>> gain for frequency) * 0.75 (over 20-ish bands, going from highest to >>>> lowest). >>>> >>>> Which works pretty good using audacities 15 band mutiband eq and a >>>> value closer to 0.60. But I'm wanting something less step ladder and >>>> needing only one or two values (with defaults) on the effects >>>> initiation. >>>> >>>> Not that I know if nyquist supports it, but some sort of sin / cos arc >>>> averaged with the linear model to determine the depth of the arc. >>>> Based on the bottom right quadrant of a circle from lowest Hz to >>>> highest Hz. Or something like that. Perhaps some averaging to 2 line >>>> + 1 arc / 3 or 1 arc + 2 line / 3 type slider to tweak it. It's just >>>> the implementation of actually doing the eq that seems problematic >>>> right now. At a minimum the math for x^2+y^2=r^2 seems to be >>>> implemented. Where r is the max frequency, x is the current frequency >>>> and y the unknown would be scaled to the gain adjustment ((y/max >>>> frequency)*dB). But it's not that math that's got me stumped. It's >>>> how to use the result to affect the eq with the least issues. >>>> >>>> - James >>>> >>> OK, you could try the NBAND-RANGE function. Here, I believe frequency >>> bands are geometrically spaced rather than linear, but you can compute >>> an array of gains. If you tell me whether you are using Lisp or SAL, I >>> think I can send a small example that computes a set of gains for >>> NBAND-RANGE. >>> >>> (I still think for a few dB, you are better off with only a few bands, >>> but if you like the sound, that's the ultimate test.) >>> >>> -Roger > > ------------------------------------------------------------------------------ > Nokia and AT&T present the 2010 Calling All Innovators-North America contest > Create new apps & games for the Nokia N8 for consumers in U.S. and Canada > $10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing > Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store > http://p.sf.net/sfu/nokia-dev2dev > _______________________________________________ > Audacity-nyquist mailing list > Aud...@li... > https://lists.sourceforge.net/lists/listinfo/audacity-nyquist > |