vf_colormatrix: calculate coefficients only once

calc_coefficients is no longer being called every frame
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/vf_colormatrix.c

@@ -187,6 +187,8 @@ static av_cold int init(AVFilterContext *ctx)
         return AVERROR(EINVAL);
     }
 
+    calc_coefficients(ctx);
+
     return 0;
 }
 
@@ -400,8 +402,6 @@ static int filter_frame(AVFilterLink *link, AVFrame *in)
     case COLOR_MODE_BT601    : av_frame_set_colorspace(out, AVCOL_SPC_BT470BG)  ; break;
     }
 
-    calc_coefficients(ctx);
-
     td.src = in;
     td.dst = out;
     td.c2 = color->yuv_convert[color->mode][0][1];