oggstream: add a flag to say whether start granule clamping is to be done

ext/ogg/gstoggstream.c

@@ -1874,6 +1874,7 @@ setup_opus_mapper (GstOggStream * pad, ogg_packet * packet)
   pad->granuleshift = 0;
   pad->n_header_packets = 2;
   pad->first_granpos = -1;
+  pad->forbid_start_clamping = TRUE;
 
   /* pre-skip is in samples at 48000 Hz, which matches granule one for one */
   pad->granule_offset = -GST_READ_UINT16_LE (packet->packet + 10);

ext/ogg/gstoggstream.h

@@ -70,6 +70,7 @@ struct _GstOggStream
   gint bitrate;
   guint64 total_time;
   gboolean is_sparse;
+  gboolean forbid_start_clamping;
 
   GstCaps *caps;