Add option to exchange the left and right stereo channels. Patch by Dave Chapman and Martin Sägmüller. Also add manual entry (by Michael Giacomelli). Note that this setting will confuse non-software effect options like channel balance. This should be addressed in a future commit.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@30837 a1c6a512-1295-4272-9138-f99709370657

apps/dsp.c

@@ -1175,6 +1175,18 @@ static void channels_process_sound_chan_karaoke(int count, int32_t *buf[])
 }
 #endif /* DSP_HAVE_ASM_SOUND_CHAN_KARAOKE */
 
+static void channels_process_sound_chan_swap(int count, int32_t *buf[])
+{
+    int32_t *sl = buf[0], *sr = buf[1];
+
+    while (count-- > 0)
+    {
+        int32_t ch = *sl;
+        *sl++ = *sr;
+        *sr++ = ch;
+    }
+}
+
 static void dsp_set_channel_config(int value)
 {
     static const channels_process_fn_type channels_process_functions[] =
@@ -1186,6 +1198,7 @@ static void dsp_set_channel_config(int value)
         [SOUND_CHAN_MONO_LEFT]  = channels_process_sound_chan_mono_left,
         [SOUND_CHAN_MONO_RIGHT] = channels_process_sound_chan_mono_right,
         [SOUND_CHAN_KARAOKE]    = channels_process_sound_chan_karaoke,
+        [SOUND_CHAN_SWAP]       = channels_process_sound_chan_swap,
     };
 
     if ((unsigned)value >= ARRAYLEN(channels_process_functions) ||

apps/lang/english.lang

@@ -12903,3 +12903,20 @@
     *: "Cancel Sleep Timer"
   </voice>
 </phrase>
+<phrase>
+  id: LANG_CHANNEL_SWAP
+  desc: in sound_settings
+  user: core
+  <source>
+    *: none
+    swcodec: "Swap channels"
+  </source>
+  <dest>
+    *: none
+    swcodec: "Swap channels"
+  </dest>
+  <voice>
+    *: none
+    swcodec: "Swap channels"
+  </voice>
+</phrase>

apps/settings_list.c

@@ -678,11 +678,12 @@ const struct settings_list settings[] = {
 
     CHOICE_SETTING(F_SOUNDSETTING, channel_config, LANG_CHANNEL_CONFIGURATION,
                    0,"channels",
-                   "stereo,mono,custom,mono left,mono right,karaoke",
-                   sound_set_channels, 6,
+                   "stereo,mono,custom,mono left,mono right,karaoke,swap",
+                   sound_set_channels, 7,
                    ID2P(LANG_CHANNEL_STEREO), ID2P(LANG_CHANNEL_MONO),
                    ID2P(LANG_CHANNEL_CUSTOM), ID2P(LANG_CHANNEL_LEFT),
-                   ID2P(LANG_CHANNEL_RIGHT), ID2P(LANG_CHANNEL_KARAOKE)),
+                   ID2P(LANG_CHANNEL_RIGHT), ID2P(LANG_CHANNEL_KARAOKE),
+                   ID2P(LANG_CHANNEL_SWAP)),
     SOUND_SETTING(F_SOUNDSETTING, stereo_width, LANG_STEREO_WIDTH,
                   "stereo_width", SOUND_STEREO_WIDTH),
 #ifdef AUDIOHW_HAVE_DEPTH_3D

manual/configure_rockbox/sound_settings.tex

@@ -169,6 +169,8 @@ change to customise your listening experience.
           to make the singer sound centrally placed, this often (but not 
           always) has the effect of removing the voice track from a song. This 
           setting also very often has other undesirable effects on the sound.
+      \item[Swap Channels]
+          Exchanges the left and right channels.          
   \end{description}
 
 \section{Stereo Width}