[FFmpeg-cvslog] lavr: mix front center channel as indicated in the ATSC A/ 52 specification.

[Tim Walker]

ffmpeg | branch: master | Tim Walker <tdskywalker at gmail.com> | Wed Jan 15 00:18:19 2014 +0000| [76a75c523cd3c63560185394a0a5cd7249db962a] | committer: Tim Walker

lavr: mix front center channel as indicated in the ATSC A/52 specification.

When mixing 3 front channels into 2, the center channel is mixed into left and right with the center mix level, not -3dB.

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=76a75c523cd3c63560185394a0a5cd7249db962a
---

 libavresample/audio_mix_matrix.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/libavresample/audio_mix_matrix.c b/libavresample/audio_mix_matrix.c
index 8da1b48..487869b 100644
--- a/libavresample/audio_mix_matrix.c
+++ b/libavresample/audio_mix_matrix.c
@@ -126,8 +126,13 @@ int avresample_build_matrix(uint64_t in_layout, uint64_t out_layout,
     /* mix front center to front left/right */
     if (unaccounted & AV_CH_FRONT_CENTER) {
         if ((out_layout & AV_CH_LAYOUT_STEREO) == AV_CH_LAYOUT_STEREO) {
-            matrix[FRONT_LEFT ][FRONT_CENTER] += M_SQRT1_2;
-            matrix[FRONT_RIGHT][FRONT_CENTER] += M_SQRT1_2;
+            if ((in_layout & AV_CH_LAYOUT_STEREO) == AV_CH_LAYOUT_STEREO) {
+                matrix[FRONT_LEFT ][FRONT_CENTER] += center_mix_level;
+                matrix[FRONT_RIGHT][FRONT_CENTER] += center_mix_level;
+            } else {
+                matrix[FRONT_LEFT ][FRONT_CENTER] += M_SQRT1_2;
+                matrix[FRONT_RIGHT][FRONT_CENTER] += M_SQRT1_2;
+            }
         } else
             return AVERROR_PATCHWELCOME;
     }