Filterdetail, Plot, and Filtergraph

MuShoo's icon

The documentation on Plot/Filtergraph is confusing me, so I have a quick question: Is it possible to use a Filtergraph with multiple filters (or multiple filtergraphs' list outputs, shoved together in one long list) into Filterdetail, and show this cascaded filter on a Plot object? If it is, I can't seem to figure it out.

Arvid Tomayko's icon

No - because, frustratingly, there is no easy object to turn biquad filter coefs into a list plot~ can plot. However, what i do is whenever i need to update the filter response curve in my plot~ from my filtergraph~, i query the gain of the filtergraph~ for each point i want to plot with, eg [uzi 512]'s count output * (sample_rate/2/511), collect that into a list with [zl 512 group 512], and send that to an input of plot~. (don't forget the 1st numerical argument of zl, otherwise your list will always be truncated to 256 members and you'll be very confused)

MuShoo's icon

That sounds a bit too intense for me - I have anywhere from 1 to 100 (or more) filtergraph~s hiding in poly~s that I'd have to query - would get really ugly, really fast. I guess I'll just keep using another filtergraph~ for viewing the combined plots.

carltonia's icon

Hi i've been using Max MSP for about a year now, this is my first forum post - firstly I want to say how helpful this resource is - but i'm getting stuck on this also.

I want to overlay a visual of a filtergraph~ over a plot~ of the spectrum analysis - similar to the EQ in Presonus Studio One. I have tried to do this the easy way - setting the alpha of the Plot bg to 0 and placing it over the filtergraph - but I can't get the thing to line up properly - ie setting grids at 10Hz 100Hz and 1000Hz are always offset - I've played around in the Inspector making the range of each match but they just wont line up... Any ideas?

Do I need to dump the output of the Filtergraph into the Plot and display it as a second graph? - this seems most logical - but i'm struggling to work it out.

Any advice would be most appreciated

Chris

Arvid Tomayko's icon

yeah - dump it. that's what i do. Not the fastest thing in the world, but it works. Alternately you could use this info http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt to write a javascript or java object that calculates the frequency response of a filter from the coefs output by the filtergraph~ and outputs it as a list of points for plot~. This would be somewhat involved if you're not an experienced programmer, but it can certainly be done.

carltonia's icon

Thats perfect, i'm testing it now and it will work fine for what i need, just needs a bit of tweaking. Humble thanks