caps: Use default audio channel layouts for some codecs

For a few white-listed codecs, use default fallback channel
layouts when ffmpeg doesn't inform us.

1 files changed, 21 insertions, 3 deletions

diff --git a/ext/ffmpeg/gstffmpegcodecmap.c b/ext/ffmpeg/gstffmpegcodecmap.c
index 5427a53..f380d8c 100644
--- a/ext/ffmpeg/gstffmpegcodecmap.c
+++ b/ext/ffmpeg/gstffmpegcodecmap.c
@@ -321,14 +321,32 @@ gst_ff_aud_caps_new (AVCodecContext * context, enum CodecID codec_id,
   /* fixed, non-probing context */
   if (context != NULL && context->channels != -1) {
     GstAudioChannelPosition *pos;
+    guint64 channel_layout = context->channel_layout;
+
+    if (channel_layout == 0) {
+      const guint64 default_channel_set[] = {
+        0, 0, CH_LAYOUT_SURROUND, CH_LAYOUT_QUAD, CH_LAYOUT_5POINT0,
+        CH_LAYOUT_5POINT1, 0, CH_LAYOUT_7POINT1
+      };
+
+      switch (codec_id) {
+        case CODEC_ID_EAC3:
+        case CODEC_ID_AC3:
+        case CODEC_ID_DTS:
+          if (context->channels > 0
+              && context->channels < G_N_ELEMENTS (default_channel_set))
+            channel_layout = default_channel_set[context->channels - 1];
+          break;
+        default:
+          break;
+      }
+    }
 
     caps = gst_caps_new_simple (mimetype,
         "rate", G_TYPE_INT, context->sample_rate,
         "channels", G_TYPE_INT, context->channels, NULL);
 
-    pos =
-        gst_ff_channel_layout_to_gst (context->channel_layout,
-        context->channels);
+    pos = gst_ff_channel_layout_to_gst (channel_layout, context->channels);
     if (pos != NULL) {
       gst_audio_set_channel_positions (gst_caps_get_structure (caps, 0), pos);
       g_free (pos);