[SCM] libav/experimental: 10l: reverse the biquad coefficients.

[siretart at users.alioth.debian.org]

The following commit has been merged in the experimental branch:
commit 98cfadd648bfb2ab48e4c18d832e946a1ba050c8
Author: Justin Ruggles <justin.ruggles at gmail.com>
Date:   Fri Jan 21 20:59:20 2011 +0000

    10l: reverse the biquad coefficients.
    
    I did not notice that the filter implementation uses a reversed history state.
    
    Signed-off-by: Janne Grunau <janne-ffmpeg at jannau.net>

diff --git a/libavcodec/iirfilter.c b/libavcodec/iirfilter.c
index 832559c..46b4973 100644
--- a/libavcodec/iirfilter.c
+++ b/libavcodec/iirfilter.c
@@ -137,15 +137,15 @@ static int biquad_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c,
 
     if (filt_mode == FF_FILTER_MODE_HIGHPASS) {
         c->gain  =  ((1.0 + cos_w0) / 2.0)  / a0;
-        x0       = (-(1.0 + cos_w0))        / a0;
-        x1       =  ((1.0 + cos_w0) / 2.0)  / a0;
+        x0       =  ((1.0 + cos_w0) / 2.0)  / a0;
+        x1       = (-(1.0 + cos_w0))        / a0;
     } else { // FF_FILTER_MODE_LOWPASS
         c->gain  =  ((1.0 - cos_w0) / 2.0)  / a0;
-        x0       =   (1.0 - cos_w0)         / a0;
-        x1       =  ((1.0 - cos_w0) / 2.0)  / a0;
+        x0       =  ((1.0 - cos_w0) / 2.0)  / a0;
+        x1       =   (1.0 - cos_w0)         / a0;
     }
-    c->cy[0] =  (2.0 *  cos_w0)        / a0;
-    c->cy[1] = (-1.0 + (sin_w0 / 2.0)) / a0;
+    c->cy[0] = (-1.0 + (sin_w0 / 2.0)) / a0;
+    c->cy[1] =  (2.0 *  cos_w0)        / a0;
 
     // divide by gain to make the x coeffs integers.
     // during filtering, the delay state will include the gain multiplication

-- 
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