transratio question

    MaxMSP
    barry threw's icon
    barry threw's icon
    barry threw
    Nov 13 2008 | 4:40 am
    Hello friends,
    In many example patches, like the transposition playground, I see a sub-patcher called "transratio".
    It is an expr with the following formula... ((440. * exp(.057762265 * $f1))* 0.002273) that serves the purpose of turning pitch changes into transposition multipliers.
    The issue is that multiplying by 0.002273 is the same as dividing by 440. so you end up multiplying and then dividing by 440.
    In the phase vocoder example by Dudas and Cort on the c74 site, this same patcher is used, but its even more explicit: expr ((440. * exp(.057762265 * $f1))/ 440.)
    Now, Les and Richard are two gentlemen that history tells me don't do things for no reason. However, I can't figure out why on earth this formula multiplies and then divides by 440. Taking those two statements out seems to yield the same results.
    Any help anyone?
    barry threw Media Art and Technology
    San Francisco, CA Work: 857-544-3967 Email: bthrew (at) gmail (dot) com Web: www.barrythrew.com
    • jayrope's icon
      jayrope's icon
      jayrope
      Nov 13 2008 | 6:20 am
      multiplication is less expensive computing, than multiplication. it's mentioned somewhere in the tutorials. jrp
      Share
    • barry threw's icon
      barry threw's icon
      barry threw
      Nov 13 2008 | 7:31 am
      While true, you are missing the forrest. When you multiply and then divide by the same thing it cancels out.
      I'm tending to think its just a "typo", but it's strange to me that it appeared in two separate patches...I'm just making sure I'm not crazy.
      bt
      On Nov 12, 2008, at 10:20 PM, jayrope wrote:
      > it seems, that multiplication is less expensive computing, than > multiplication. it's mentioned somewhere in the tutorials. > jrp > -- > --- > fiction-induced heat > on too many websites to name
      barry threw Media Art and Technology
      San Francisco, CA Work: 857-544-3967 Email: bthrew (at) gmail (dot) com Web: www.barrythrew.com
    • jayrope's icon
      jayrope's icon
      jayrope
      Nov 13 2008 | 8:00 am
      Man, how i miss the forrest, spending way too much time in the city centre.
    • Peter Castine's icon
      Peter Castine's icon
      Peter Castine
      Nov 13 2008 | 1:17 pm
      The self-canceling 440.0*0.002273 is removed in Max 5.
      < & Xoaz are great Max developers, but even the best of us does something unnecessary once in a while. The technical Latin term is "poopus cranialus"
    • kjg's icon
      kjg's icon
      kjg
      Nov 13 2008 | 2:06 pm
      The only reason to use this number in a pitch related formula would be as the "A=440" (or 436, or 442 etc) reference pitch, right?
      I use this for calculating transposition ratios. [expr pow(2,($f1/12))]
      the 12 can be replaced with another number for different equal temperaments.
      regards, kjg
    • Tj Shredder's icon
      Tj Shredder's icon
      Tj Shredder
      Nov 14 2008 | 12:01 pm
      barry threw schrieb: > Taking those two statements > out seems to yield the same results.
      I have done that as well, and it works. Simplifying the world never hurts. No problem for me, and never expect the gurus to find always the shortest path. They do mostly though and that's fine...
      Stefan
      -- Stefan Tiedje------------x------- --_____-----------|-------------- --(_|_ ----|-----|-----()------- -- _|_)----|-----()-------------- ----------()--------www.ccmix.com