Filterdetail, Plot, and Filtergraph


    Sep 05 2012 | 6:31 pm
    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.

    • Sep 09 2012 | 3:09 pm
      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)
    • Sep 09 2012 | 3:26 pm
      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.
    • Nov 07 2012 | 1:07 pm
      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
    • Nov 08 2012 | 4:40 am
      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.
    • Nov 08 2012 | 8:49 pm
      Thats perfect, i'm testing it now and it will work fine for what i need, just needs a bit of tweaking. Humble thanks