flvmux: only write full metadata at start

... rather than having (potentially) unnecessary duplicates written all over,
or even contradictory varying filesize info, or duration info that will not
be rewritten upon header rewrite.

gst/flv/gstflvmux.c

@@ -644,7 +644,7 @@ gst_flv_mux_create_number_script_value (const gchar * name, gdouble value)
 }
 
 static GstBuffer *
-gst_flv_mux_create_metadata (GstFlvMux * mux)
+gst_flv_mux_create_metadata (GstFlvMux * mux, gboolean full)
 {
   const GstTagList *tags;
   GstBuffer *script_tag, *tmp;
@@ -687,6 +687,9 @@ gst_flv_mux_create_metadata (GstFlvMux * mux)
   GST_WRITE_UINT32_BE (data + 1, n_tags);
   script_tag = gst_buffer_join (script_tag, tmp);
 
+  if (!full)
+    goto tags;
+
   /* Some players expect the 'duration' to be always set. Fill it out later,
      after querying the pads or after getting EOS */
   if (!mux->streamable) {
@@ -707,6 +710,7 @@ gst_flv_mux_create_metadata (GstFlvMux * mux)
     GST_DEBUG_OBJECT (mux, "not preallocating index, streamable mode");
   }
 
+tags:
   for (i = 0; tags && i < n_tags; i++) {
     const gchar *tag_name =
         gst_structure_nth_field_name ((const GstStructure *) tags, i);
@@ -745,6 +749,9 @@ gst_flv_mux_create_metadata (GstFlvMux * mux)
     }
   }
 
+  if (!full)
+    goto end;
+
   if (mux->duration == GST_CLOCK_TIME_NONE) {
     GSList *l;
 
@@ -926,6 +933,13 @@ gst_flv_mux_create_metadata (GstFlvMux * mux)
     tags_written++;
   }
 
+end:
+
+  if (!tags_written) {
+    gst_buffer_unref (script_tag);
+    goto exit;
+  }
+
   tmp = gst_buffer_new_and_alloc (2 + 0 + 1);
   data = GST_BUFFER_DATA (tmp);
   data[0] = 0;                  /* 0 byte size */
@@ -946,6 +960,7 @@ gst_flv_mux_create_metadata (GstFlvMux * mux)
 
   GST_WRITE_UINT32_BE (data + 11 + 13 + 1, tags_written);
 
+exit:
   return script_tag;
 }
 
@@ -1089,7 +1104,7 @@ gst_flv_mux_write_header (GstFlvMux * mux)
   GstFlowReturn ret;
 
   header = gst_flv_mux_create_header (mux);
-  metadata = gst_flv_mux_create_metadata (mux);
+  metadata = gst_flv_mux_create_metadata (mux, TRUE);
   video_codec_data = NULL;
   audio_codec_data = NULL;
 
@@ -1407,8 +1422,9 @@ gst_flv_mux_handle_buffer (GstCollectPads2 * pads, GstCollectData2 * cdata,
   }
 
   if (mux->new_tags) {
-    GstBuffer *buf = gst_flv_mux_create_metadata (mux);
-    gst_flv_mux_push (mux, buf);
+    GstBuffer *buf = gst_flv_mux_create_metadata (mux, FALSE);
+    if (buf)
+      gst_flv_mux_push (mux, buf);
     mux->new_tags = FALSE;
   }