[0.11] gst-plugins-good: audiofx: Use most common convention for definitions of IIR filter coefficients.

Sebastian Dröge slomo at kemper.freedesktop.org
Wed Jan 11 06:24:21 PST 2012


Module: gst-plugins-good
Branch: 0.11
Commit: 56353e24d2f404269c7662eb4549b4c58b449d49
URL:    http://cgit.freedesktop.org/gstreamer/gst-plugins-good/commit/?id=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 swapped, and did not have the minus signs.

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

---

 gst/audiofx/audiochebband.c           |   74 +++++++++++++++++----------------
 gst/audiofx/audiocheblimit.c          |   46 +++++++++++---------
 gst/audiofx/audiofxbaseiirfilter.c    |   51 +++++++++++-----------
 gst/audiofx/audioiirfilter.c          |    4 +-
 tests/check/elements/audioiirfilter.c |    6 +-
 5 files changed, 93 insertions(+), 88 deletions(-)

Diff:   http://cgit.freedesktop.org/gstreamer/gst-plugins-good/diff/?id=56353e24d2f404269c7662eb4549b4c58b449d49


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