qtdemux: Export max bitrate for AMR-NB/-WB streams

This parses the 'damr' atom if present, and exports the maximum bitrate
of the stream using the mode set field to determine the highest bitrate
frame type that might be present.

https://bugzilla.gnome.org/show_bug.cgi?id=620186

diff --git a/gst/isomp4/qtdemux.c b/gst/isomp4/qtdemux.c
index 5f6b077..bafcf96 100644 (file)
--- a/gst/isomp4/qtdemux.c
+++ b/gst/isomp4/qtdemux.c
@@ -6136,6 +6136,63 @@ less_than (gconstpointer a, gconstpointer b)
   return *av - *bv;
 }
 
+#define AMR_NB_ALL_MODES        0x81ff
+#define AMR_WB_ALL_MODES        0x83ff
+static guint
+qtdemux_parse_amr_bitrate (GstBuffer * buf, gboolean wb)
+{
+  /* The 'damr' atom is of the form:
+   *
+   * | vendor | decoder_ver | mode_set | mode_change_period | frames/sample |
+   *    32 b       8 b          16 b           8 b                 8 b
+   *
+   * The highest set bit of the first 7 (AMR-NB) or 8 (AMR-WB) bits of mode_set
+   * represents the highest mode used in the stream (and thus the maximum
+   * bitrate), with a couple of special cases as seen below.
+   */
+
+  /* Map of frame type ID -> bitrate */
+  static const guint nb_bitrates[] = {
+    4750, 5150, 5900, 6700, 7400, 7950, 10200, 12200
+  };
+  static const guint wb_bitrates[] = {
+    6600, 8850, 12650, 14250, 15850, 18250, 19850, 23050, 23850
+  };
+  const guint8 *data = GST_BUFFER_DATA (buf);
+  guint size = QT_UINT32 (data), max_mode;
+  guint16 mode_set;
+
+  if (GST_BUFFER_SIZE (buf) != 0x11) {
+    GST_DEBUG ("Atom should have size 0x11, not %u", size);
+    goto bad_data;
+  }
+
+  if (QT_FOURCC (data + 4) != GST_MAKE_FOURCC ('d', 'a', 'm', 'r')) {
+    GST_DEBUG ("Unknown atom in %" GST_FOURCC_FORMAT,
+        GST_FOURCC_ARGS (QT_UINT32 (data + 4)));
+    goto bad_data;
+  }
+
+  mode_set = QT_UINT16 (data + 13);
+
+  if (mode_set == (wb ? AMR_WB_ALL_MODES : AMR_NB_ALL_MODES))
+    max_mode = 7 + (wb ? 1 : 0);
+  else
+    /* AMR-NB modes fo from 0-7, and AMR-WB modes go from 0-8 */
+    max_mode = g_bit_nth_msf ((gulong) mode_set & (wb ? 0x1ff : 0xff), -1);
+
+  if (max_mode == -1) {
+    GST_DEBUG ("No mode indication was found (mode set) = %x",
+        (guint) mode_set);
+    goto bad_data;
+  }
+
+  return wb ? wb_bitrates[max_mode] : nb_bitrates[max_mode];
+
+bad_data:
+  return 0;
+}
+
 /* parse the traks.
  * With each track we associate a new QtDemuxStream that contains all the info
  * about the trak.
@@ -6759,6 +6816,7 @@ qtdemux_parse_trak (GstQTDemux * qtdemux, GNode * trak)
   } else if (stream->subtype == FOURCC_soun) {
     int version, samplesize;
     guint16 compression_id;
+    gboolean amrwb = FALSE;
 
     offset = 32;
     if (len < 36)
@@ -7126,15 +7184,29 @@ qtdemux_parse_trak (GstQTDemux * qtdemux, GNode * trak)
               "samplesize", G_TYPE_INT, samplesize, NULL);
           break;
         }
+        case FOURCC_sawb:
+          /* Fallthrough! */
+          amrwb = TRUE;
         case FOURCC_samr:
         {
           gint len = QT_UINT32 (stsd_data);
 
           if (len > 0x34) {
             GstBuffer *buf = gst_buffer_new_and_alloc (len - 0x34);
+            guint bitrate;
 
             memcpy (GST_BUFFER_DATA (buf), stsd_data + 0x34, len - 0x34);
 
+            /* If we have enough data, let's try to get the 'damr' atom. See
+             * the 3GPP container spec (26.244) for more details. */
+            if ((len - 0x34) > 8 &&
+                (bitrate = qtdemux_parse_amr_bitrate (buf, amrwb))) {
+              if (!list)
+                list = gst_tag_list_new ();
+              gst_tag_list_add (list, GST_TAG_MERGE_REPLACE,
+                  GST_TAG_MAXIMUM_BITRATE, bitrate, NULL);
+            }
+
             gst_caps_set_simple (stream->caps,
                 "codec_data", GST_TYPE_BUFFER, buf, NULL);
             gst_buffer_unref (buf);