[Bug 632664] [0.11] audioiirfilter: nonstandard definition of 'a' and 'b' coefficients for IIR filters

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=632664
  GStreamer | gst-plugins-good | git

Sebastian Dröge <slomo> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #4 from Sebastian Dröge <slomo at circular-chaos.org> 2012-01-11 14:24:32 UTC ---
commit 56353e24d2f404269c7662eb4549b4c58b449d49
Author: Leo Singer <leo.singer at ligo.org>
Date:   Wed Oct 20 02:17:43 2010 -0700

    audiofx: Use most common convention for definitions of IIR filter
coefficients.

    Most signal processing texts, including MATLAB, use the following
convention for IIR filter coefficients:

    a_0 y[n] + a_1 y[n-1] + ... + a_M y[n-M] = b_0 x[n] + b_1 x[n-1] + ... +
b[N] x[n-N]

    Usually, a_0 is set to 1 because the coefficients can always be rescaled,
giving

    y[n] = b_0 x[n] + b_1 x[n-1] + ... + b[N] x[n-N] - a_1 y[n-1] - ... - a_M
y[n-M]

    The convention that was previously used by audiofxbaseiirfilter and derived
class had the a and b coefficients swapp

    This change makes the audiofx plugin use the more common convention
described above.

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