lavr: fix mixing matrix reduction when normalization is disabled

gistfile1.diff

From c315796cd31782b98720faff17830bc1f9b76209 Mon Sep 17 00:00:00 2001
From: Justin Ruggles <[email protected]>
Date: Sun, 27 Jan 2013 14:47:54 -0500
Subject: [PATCH] lavr: fix mixing matrix reduction when normalization is disabled

In some cases when an input contributes fully to the corresponding
output, other inputs may also contribute to the same output. This is the
case, for example, for the default 5.1 to stereo downmix matrix without
normalization.
---
 libavresample/audio_mix.c |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/libavresample/audio_mix.c b/libavresample/audio_mix.c
index 9a5ffcc..806abe3 100644
--- a/libavresample/audio_mix.c
+++ b/libavresample/audio_mix.c
@@ -568,11 +568,22 @@ static void reduce_matrix(AudioMix *am, const double *matrix, int stride)
         int skip = 1;
 
         for (o = 0; o < am->out_channels; o++) {
+            int i0;
             if ((o != i && matrix[o * stride + i] != 0.0) ||
                 (o == i && matrix[o * stride + i] != 1.0)) {
                 skip = 0;
                 break;
             }
+            /* if the input contributes fully to the output, also check that no
+               other inputs contribute to this output */
+            if (o == i) {
+                for (i0 = 0; i0 < am->in_channels; i0++) {
+                    if (i0 != i && matrix[o * stride + i0] != 0.0) {
+                        skip = 0;
+                        break;
+                    }
+                }
+            }
         }
         if (skip) {
             am->input_skip[i] = 1;
-- 
1.7.1