use default alsa channel map for alsa devices

git-svn-id: file:///home/lennart/svn/public/pulseaudio/trunk@851 fefdeb5f-60dc-0310-8127-8f9354f1896f

1 files changed, 44 insertions, 0 deletions

diff --git a/src/modules/alsa-util.c b/src/modules/alsa-util.c
index 8bb33c2f..4c9cde9e 100644
--- a/src/modules/alsa-util.c
+++ b/src/modules/alsa-util.c
@@ -340,3 +340,47 @@ snd_mixer_elem_t *pa_alsa_find_elem(snd_mixer_t *mixer, const char *name) {
 
     return elem;
 }
+
+pa_channel_map* pa_alsa_channel_map_init_auto(pa_channel_map *m, unsigned channels) {
+    assert(m);
+    assert(channels > 0);
+    assert(channels <= PA_CHANNELS_MAX);
+
+    pa_channel_map_init(m);
+
+    m->channels = channels;
+
+    /* The standard ALSA channel order */
+    
+    switch (channels) {
+        case 1:
+            m->map[0] = PA_CHANNEL_POSITION_MONO;
+            return m;
+
+        case 8:
+            m->map[6] = PA_CHANNEL_POSITION_SIDE_LEFT;
+            m->map[7] = PA_CHANNEL_POSITION_SIDE_RIGHT;
+            /* Fall through */
+
+        case 6:
+            m->map[5] = PA_CHANNEL_POSITION_LFE;
+            /* Fall through */
+            
+        case 5:
+            m->map[4] = PA_CHANNEL_POSITION_FRONT_CENTER;
+            /* Fall through */
+            
+        case 4:
+            m->map[2] = PA_CHANNEL_POSITION_REAR_LEFT;
+            m->map[3] = PA_CHANNEL_POSITION_REAR_RIGHT;
+            /* Fall through */
+            
+        case 2:
+            m->map[0] = PA_CHANNEL_POSITION_FRONT_LEFT;
+            m->map[1] = PA_CHANNEL_POSITION_FRONT_RIGHT;
+            return m;
+
+        default:
+            return NULL;
+    }
+}