rockbox, Swap Channels

diff --git a/apps/lang/english.lang b/apps/lang/english.lang
index 627fda8..ef715c7 100644
--- apps/lang/english.lang
+++ apps/lang/english.lang
@@ -12993,3 +12993,20 @@
     *: "Restart Sleep Timer On Keypress"
   </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>
diff --git a/apps/dsp.c b/apps/dsp.c
index 00de511..40cb1b6 100644
--- apps/dsp.c
+++ apps/dsp.c
@@ -1119,6 +1119,18 @@
 }
 #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[] =
@@ -1130,6 +1142,7 @@
         [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) ||
diff --git a/apps/settings_list.c b/apps/settings_list.c
index 44295ac..03d49e4 100644
--- apps/settings_list.c
+++ apps/settings_list.c
@@ -696,11 +696,12 @@

     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
diff --git a/firmware/export/audiohw.h b/firmware/export/audiohw.h
index 304c5aa..c8c87dd 100644
--- firmware/export/audiohw.h
+++ firmware/export/audiohw.h
@@ -346,6 +346,7 @@
     SOUND_CHAN_MONO_LEFT,
     SOUND_CHAN_MONO_RIGHT,
     SOUND_CHAN_KARAOKE,
+    SOUND_CHAN_SWAP,
     SOUND_CHAN_NUM_MODES,
 };