Channel reordering according to the WG-4 specification, courtesy of

Heiko Panther.

diff --git a/modules/audio_filter/converter/a52tofloat32.c b/modules/audio_filter/converter/a52tofloat32.c
index c6eb5b3025ba409281b9a073e1e7bc0fa785cbd7..b579e51a83f1e2c8d8c8cabcee6c87b933387032 100644 (file)
--- a/modules/audio_filter/converter/a52tofloat32.c
+++ b/modules/audio_filter/converter/a52tofloat32.c
@@ -4,7 +4,7 @@
  *   (http://liba52.sf.net/).
  *****************************************************************************
  * Copyright (C) 2001, 2002 VideoLAN
- * $Id: a52tofloat32.c,v 1.7 2002/11/18 23:00:41 massiot Exp $
+ * $Id: a52tofloat32.c,v 1.8 2002/11/21 23:06:08 massiot Exp $
  *
  * Authors: Gildas Bazin <gbazin@netcourrier.com>
  *          Christophe Massiot <massiot@via.ecp.fr>
@@ -215,13 +215,44 @@ static int Create( vlc_object_t * _p_filter )
  *****************************************************************************/
 static void Interleave( float * p_out, const float * p_in, int i_nb_channels )
 {
+    /* We do not only have to interleave, but also reorder the channels
+     * Channel reordering according to number of output channels of libA52
+     * The reordering needs to be different for different channel configurations
+     * (3F2R, 1F2R etc), so this is only temporary.
+     * The WG-4 order is appropriate for stereo, quadrophonia, and 5.1 surround.
+     *
+     * 6 channel mode
+     * channel liba52 order    WG-4 order
+     * 0       LFE             // L
+     * 1       L               // R
+     * 2       C               // LS
+     * 3       R               // RS
+     * 4       LS              // C
+     * 5       RS              // LFE
+     *
+     * The liba52 moves channels to the front if there are unused spaces, so
+     * there is no gap between channels. The translation table says which
+     * channel of the new stream [use the new channel # as index] is taken
+     * from which original channel [use the number from the array to address
+     * the original channel].
+     */
+    
+    static const int translation[7][6] =
+    {{ 0, 0, 0, 0, 0, 0 },     /* 0 channels (rarely used) */
+    { 0, 0, 0, 0, 0, 0 },      /* 1 ch */
+    { 0, 1, 0, 0, 0, 0 },      /* 2 */
+    { 1, 2, 0, 0, 0, 0 },      /* 3 */
+    { 1, 3, 2, 0, 0, 0 },      /* 4 */
+    { 1, 3, 4, 2, 0, 0 },      /* 5 */
+    { 1, 3, 4, 5, 2, 0 }};     /* 6 */
+       
     int i, j;
-
     for ( j = 0; j < i_nb_channels; j++ )
     {
         for ( i = 0; i < 256; i++ )
         {
-            p_out[i * i_nb_channels + j] = p_in[j * 256 + i];
+            p_out[i * i_nb_channels + translation[i_nb_channels][j]]
+                    = p_in[j * 256 + i];
         }
     }
 }