update 5.1 downsample patch so that channel mapping works

patches/6to2channel-resample.patch

 Index: libavcodec/resample.c
 ===================================================================
---- libavcodec/resample.c	(revision 11509)
+--- libavcodec/resample.c	(revision 22168)
 +++ libavcodec/resample.c	(working copy)
-@@ -37,6 +37,17 @@
-     int input_channels, output_channels, filter_channels;
+@@ -52,6 +52,17 @@
+     unsigned buffer_size[2];         ///< sizes of allocated buffers
  };
  
 +/*
@@ -20,7 +20,7 @@ Index: libavcodec/resample.c
  /* n1: number of samples */
  static void stereo_to_mono(short *output, short *input, int n1)
  {
-@@ -88,14 +99,43 @@
+@@ -103,14 +114,43 @@
      }
  }
  
@@ -43,14 +43,14 @@ Index: libavcodec/resample.c
 +            l = input[0];
 +            r = input[1];
 +        } else if (channels == 6) {
-+            /* 5.1 to stereo. l, c, r, ls, rs, sw */
++            /* 5.1 to stereo input: [fl, fr, c, lfe, rl, rr] */
 +            int fl,fr,c,rl,rr,lfe;
 +            fl = input[0];
-+            c = input[1];
-+            fr = input[2];
-+            rl = input[3];
-+            rr = input[4];
-+            lfe = input[5];
++            fr = input[1];
++            c = input[2];
++            lfe = input[3];
++            rl = input[4];
++            rr = input[5];
 +
 +            l = clip_short(fl + (0.5 * rl) + (0.7 * c));
 +            r = clip_short(fr + (0.5 * rr) + (0.7 * c));
@@ -69,7 +69,7 @@ Index: libavcodec/resample.c
      }
  }
  
-@@ -131,9 +171,9 @@
+@@ -150,9 +190,9 @@
  {
      ReSampleContext *s;
  
@@ -81,7 +81,7 @@ Index: libavcodec/resample.c
          return NULL;
        }
  
-@@ -205,7 +245,7 @@
+@@ -312,7 +352,7 @@
      } else if (s->output_channels >= 2) {
          buftmp3[0] = bufout[0];
          buftmp3[1] = bufout[1];