alsa: Add channel map API support

The initial support for the new ALSA chmap API.
Just translate the current chmap to GstAudioChannelPosition during the
setup.  No function to specify the channel map manually yet, so still
impossible to assign any non-standard positions or to configure in a
different order even if the hardware allows.

https://bugzilla.gnome.org/show_bug.cgi?id=709755

ext/alsa/gstalsa.c

@@ -707,3 +707,55 @@ const GstAudioChannelPosition alsa_position[][8] = {
         GST_AUDIO_CHANNEL_POSITION_SIDE_LEFT,
       GST_AUDIO_CHANNEL_POSITION_SIDE_RIGHT}
 };
+
+#ifdef SND_CHMAP_API_VERSION
+/* +1 is to make zero as holes */
+#define ITEM(x, y) \
+  [SND_CHMAP_ ## x] = GST_AUDIO_CHANNEL_POSITION_ ## y + 1
+
+static GstAudioChannelPosition gst_pos[SND_CHMAP_LAST + 1] = {
+  ITEM(MONO, MONO),
+  ITEM(FL, FRONT_LEFT),
+  ITEM(FR, FRONT_RIGHT),
+  ITEM(FC, FRONT_CENTER),
+  ITEM(RL, REAR_LEFT),
+  ITEM(RR, REAR_RIGHT),
+  ITEM(RC, REAR_CENTER),
+  ITEM(LFE, LFE1),
+  ITEM(SL, SIDE_LEFT),
+  ITEM(SR, SIDE_RIGHT),
+  ITEM(FLC, FRONT_LEFT_OF_CENTER),
+  ITEM(FRC, FRONT_RIGHT_OF_CENTER),
+  ITEM(FLW, WIDE_LEFT),
+  ITEM(FRW, WIDE_RIGHT),
+  ITEM(TC, TOP_CENTER),
+  ITEM(TFL, TOP_FRONT_LEFT),
+  ITEM(TFR, TOP_FRONT_RIGHT),
+  ITEM(TFC, TOP_FRONT_CENTER),
+  ITEM(TRL, TOP_REAR_LEFT),
+  ITEM(TRR, TOP_REAR_RIGHT),
+  ITEM(TRC, TOP_REAR_CENTER),
+  ITEM(LLFE, LFE1),
+  ITEM(RLFE, LFE2),
+  ITEM(BC, BOTTOM_FRONT_CENTER),
+  ITEM(BLC, BOTTOM_FRONT_LEFT),
+  ITEM(BRC, BOTTOM_FRONT_LEFT),
+};
+#undef ITEM
+
+gboolean alsa_chmap_to_channel_positions (const snd_pcm_chmap_t *chmap,
+					  GstAudioChannelPosition *pos)
+{
+  int c;
+
+  for (c = 0; c < chmap->channels; c++) {
+    if (chmap->pos[c] > SND_CHMAP_LAST)
+      return FALSE;
+    pos[c] = gst_pos[chmap->pos[c]];
+    if (!pos[c])
+      return FALSE;
+    pos[c]--;
+  }
+  return TRUE;
+}
+#endif /* SND_CHMAP_API_VERSION */

ext/alsa/gstalsa.h

@@ -71,5 +71,9 @@ void      gst_alsa_add_channel_reorder_map (GstObject * obj,
                                             GstCaps   * caps);
 
 extern const GstAudioChannelPosition alsa_position[][8];
+#ifdef SND_CHMAP_API_VERSION
+gboolean alsa_chmap_to_channel_positions (const snd_pcm_chmap_t *chmap,
+					  GstAudioChannelPosition *pos);
+#endif
 
 #endif /* __GST_ALSA_H__ */

ext/alsa/gstalsasink.c

@@ -896,6 +896,18 @@ gst_alsasink_prepare (GstAudioSink * asink, GstAudioRingBufferSpec * spec)
     snd_output_close (out_buf);
   }
 
+#ifdef SND_CHMAP_API_VERSION
+  if (spec->type == GST_AUDIO_RING_BUFFER_FORMAT_TYPE_RAW && alsa->channels < 9) {
+    snd_pcm_chmap_t *chmap = snd_pcm_get_chmap (alsa->handle);
+    if (chmap && chmap->channels == alsa->channels) {
+      GstAudioChannelPosition pos[8];
+      if (alsa_chmap_to_channel_positions (chmap, pos))
+	gst_audio_ring_buffer_set_channel_positions (GST_AUDIO_BASE_SINK (alsa)->ringbuffer, pos);
+    }
+    free (chmap);
+  }
+#endif /* SND_CHMAP_API_VERSION */
+
   return TRUE;
 
   /* ERRORS */

ext/alsa/gstalsasrc.c

@@ -783,6 +783,18 @@ gst_alsasrc_prepare (GstAudioSrc * asrc, GstAudioRingBufferSpec * spec)
     snd_output_close (out_buf);
   }
 
+#ifdef SND_CHMAP_API_VERSION
+  if (spec->type == GST_AUDIO_RING_BUFFER_FORMAT_TYPE_RAW && alsa->channels < 9) {
+    snd_pcm_chmap_t *chmap = snd_pcm_get_chmap (alsa->handle);
+    if (chmap && chmap->channels == alsa->channels) {
+      GstAudioChannelPosition pos[8];
+      if (alsa_chmap_to_channel_positions (chmap, pos))
+	gst_audio_ring_buffer_set_channel_positions (GST_AUDIO_BASE_SRC (alsa)->ringbuffer, pos);
+    }
+    free (chmap);
+  }
+#endif /* SND_CHMAP_API_VERSION */
+
   return TRUE;
 
   /* ERRORS */