[FFmpeg-cvslog] lavfi/af_aemphasis: remove unnecessary complex number usage

[Ganesh Ajjanagadde]

ffmpeg | branch: master | Ganesh Ajjanagadde <gajjanagadde at gmail.com> | Mon Dec 21 17:12:04 2015 -0800| [520a5d33f0ea9f8838dbc7282470db700d248065] | committer: Ganesh Ajjanagadde

lavfi/af_aemphasis: remove unnecessary complex number usage

complex is not available on all platforms. Furthermore, it is trivial to
rewrite complex number expressions to real arithmetic, and in fact
sometimes advantageous for performance reasons: by wrapping as a complex,
one forces a particular Cartesian representation that is not necessarily optimal for the purpose.

Configure dependencies also removed, and aemphasis is now available across
all platforms.

Reviewed-by: Paul B Mahol <onemda at gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=520a5d33f0ea9f8838dbc7282470db700d248065
---

 configure                  |    1 -
 libavfilter/af_aemphasis.c |   13 ++++++-------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/configure b/configure
index 54c9789..5de470c 100755
--- a/configure
+++ b/configure
@@ -2836,7 +2836,6 @@ unix_protocol_deps="sys_un_h"
 unix_protocol_select="network"
 
 # filters
-aemphasis_filter_deps="cabs cexp"
 amovie_filter_deps="avcodec avformat"
 aresample_filter_deps="swresample"
 ass_filter_deps="libass"
diff --git a/libavfilter/af_aemphasis.c b/libavfilter/af_aemphasis.c
index 2966f77..a5b8e30 100644
--- a/libavfilter/af_aemphasis.c
+++ b/libavfilter/af_aemphasis.c
@@ -18,8 +18,6 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-#include <complex.h>
-
 #include "libavutil/opt.h"
 #include "avfilter.h"
 #include "internal.h"
@@ -189,14 +187,15 @@ static inline void set_lp_rbj(BiquadD2 *bq, double fc, double q, double sr, doub
 
 static double freq_gain(BiquadCoeffs *c, double freq, double sr)
 {
-    double complex z, w;
+    double zr, zi;
 
     freq *= 2.0 * M_PI / sr;
-    w = 0 + I * freq;
-    z = 1.0 / cexp(w);
+    zr = cos(freq);
+    zi = -sin(freq);
 
-    return cabs(((double complex)c->a0 + c->a1 * z + c->a2 * z*z) /
-                ((double complex)1.0 + c->b1 * z + c->b2 * z*z));
+    /* |(a0 + a1*z + a2*z^2)/(1 + b1*z + b2*z^2)| */
+    return hypot(c->a0 + c->a1*zr + c->a2*(zr*zr-zi*zi), c->a1*zi + 2*c->a2*zr*zi) /
+           hypot(1 + c->b1*zr + c->b2*(zr*zr-zi*zi), c->b1*zi + 2*c->b2*zr*zi);
 }
 
 static int config_input(AVFilterLink *inlink)