mpegtspacketizer: Speed up descriptor parsing/packing

descriptors are stored as a GValueArray of GString. The downside is
that there is no way to "pass" ownership of a GValue to a GValueArray
which previously resulted in expensive copy/free of the (already expensive)
GString.

Here we estimate first the size of the GValueArray, then create it,
then directly use the GValue of that array.

Speeds up total SI parsing by ~30%

1 files changed, 52 insertions, 47 deletions

diff --git a/gst/mpegtsdemux/mpegtspacketizer.c b/gst/mpegtsdemux/mpegtspacketizer.c
index 23e13743e..ce146ccc1 100644
--- a/gst/mpegtsdemux/mpegtspacketizer.c
+++ b/gst/mpegtsdemux/mpegtspacketizer.c
@@ -692,14 +692,15 @@ set_descriptors_array_on_structure (GstStructure * structure, GQuark quark,
   gst_structure_id_take_value (structure, quark, &value);
 }
 
-static gboolean
+static GValueArray *
 mpegts_packetizer_parse_descriptors (MpegTSPacketizer2 * packetizer,
-    guint8 ** buffer, guint8 * buffer_end, GValueArray * descriptors)
+    guint8 ** buffer, guint8 * buffer_end)
 {
+  GValueArray *descriptors = NULL;
   guint8 length;
   guint8 *data;
-  GValue value = { 0 };
   GString *desc;
+  guint i, nb_desc = 0;
 
   data = *buffer;
 
@@ -713,14 +714,8 @@ mpegts_packetizer_parse_descriptors (MpegTSPacketizer2 * packetizer,
       goto error;
     }
 
-    /* include length */
-    desc = g_string_new_len ((gchar *) data - 2, length + 2);
     data += length;
-    /* G_TYPE_GSTRING is a GBoxed type and is used so properly marshalled from python */
-    g_value_init (&value, G_TYPE_GSTRING);
-    g_value_take_boxed (&value, desc);
-    g_value_array_append (descriptors, &value);
-    g_value_unset (&value);
+    nb_desc++;
   }
 
   if (data != buffer_end) {
@@ -729,11 +724,28 @@ mpegts_packetizer_parse_descriptors (MpegTSPacketizer2 * packetizer,
     goto error;
   }
 
+  data = *buffer;
+  descriptors = g_value_array_new (nb_desc);
+
+  for (i = 0; i < nb_desc; i++) {
+    GValue *value = &(descriptors->values[i]);
+    data++;                     /* skip tag */
+    length = *data++;
+
+    /* include length */
+    desc = g_string_new_len ((gchar *) data - 2, length + 2);
+    data += length;
+    /* G_TYPE_GSTRING is a GBoxed type and is used so properly marshalled from python */
+    g_value_init (value, G_TYPE_GSTRING);
+    g_value_take_boxed (value, desc);
+  }
+
   *buffer = data;
 
-  return TRUE;
+  return descriptors;
+
 error:
-  return FALSE;
+  return NULL;
 }
 
 GstStructure *
@@ -767,12 +779,10 @@ mpegts_packetizer_parse_cat (MpegTSPacketizer2 * packetizer,
   /* descriptors */
   desc_len = section->section_length - 4 - 8;
   gst_mpeg_descriptor_parse (&desc, data, desc_len);
-  descriptors = g_value_array_new (desc.n_desc);
-  if (!mpegts_packetizer_parse_descriptors (packetizer, &data, data + desc_len,
-          descriptors)) {
-    g_value_array_free (descriptors);
+  descriptors =
+      mpegts_packetizer_parse_descriptors (packetizer, &data, data + desc_len);
+  if (descriptors == NULL)
     goto error;
-  }
   set_descriptors_array_on_structure (cat_info, QUARK_DESCRIPTORS, descriptors);
 
   return cat_info;
@@ -910,12 +920,11 @@ mpegts_packetizer_parse_pmt (MpegTSPacketizer2 * packetizer,
       goto error;
     }
 
-    descriptors = g_value_array_new (0);
-    if (!mpegts_packetizer_parse_descriptors (packetizer,
-            &data, data + program_info_length, descriptors)) {
-      g_value_array_free (descriptors);
+    descriptors =
+        mpegts_packetizer_parse_descriptors (packetizer, &data,
+        data + program_info_length);
+    if (descriptors == NULL)
       goto error;
-    }
 
     set_descriptors_array_on_structure (pmt, QUARK_DESCRIPTORS, descriptors);
   }
@@ -1021,12 +1030,12 @@ mpegts_packetizer_parse_pmt (MpegTSPacketizer2 * packetizer,
           g_free (lang_code);
         }
 
-        descriptors = g_value_array_new (desc.n_desc);
-        if (!mpegts_packetizer_parse_descriptors (packetizer,
-                &data, data + stream_info_length, descriptors)) {
+        descriptors =
+            mpegts_packetizer_parse_descriptors (packetizer, &data,
+            data + stream_info_length);
+        if (descriptors == NULL) {
           g_value_unset (&programs);
           gst_structure_free (stream_info);
-          g_value_array_free (descriptors);
           goto error;
         }
 
@@ -1132,11 +1141,11 @@ mpegts_packetizer_parse_nit (MpegTSPacketizer2 * packetizer,
         g_free (networkname_tmp);
       }
 
-      descriptors = g_value_array_new (mpegdescriptor.n_desc);
-      if (!mpegts_packetizer_parse_descriptors (packetizer,
-              &data, data + descriptors_loop_length, descriptors)) {
+      descriptors =
+          mpegts_packetizer_parse_descriptors (packetizer, &data,
+          data + descriptors_loop_length);
+      if (!descriptors) {
         gst_structure_free (nit);
-        g_value_array_free (descriptors);
         goto error;
       }
       set_descriptors_array_on_structure (nit, QUARK_DESCRIPTORS, descriptors);
@@ -1620,11 +1629,11 @@ mpegts_packetizer_parse_nit (MpegTSPacketizer2 * packetizer,
         }
       }
 
-      descriptors = g_value_array_new (mpegdescriptor.n_desc);
-      if (!mpegts_packetizer_parse_descriptors (packetizer,
-              &data, data + descriptors_loop_length, descriptors)) {
+      descriptors =
+          mpegts_packetizer_parse_descriptors (packetizer, &data,
+          data + descriptors_loop_length);
+      if (!descriptors) {
         gst_structure_free (transport);
-        g_value_array_free (descriptors);
         goto error;
       }
 
@@ -1813,11 +1822,10 @@ mpegts_packetizer_parse_sdt (MpegTSPacketizer2 * packetizer,
         }
       }
 
-      descriptors = g_value_array_new (mpegdescriptor.n_desc);
-      if (!mpegts_packetizer_parse_descriptors (packetizer,
-              &data, data + descriptors_loop_length, descriptors)) {
+      descriptors = mpegts_packetizer_parse_descriptors (packetizer,
+          &data, data + descriptors_loop_length);
+      if (!descriptors) {
         gst_structure_free (service);
-        g_value_array_free (descriptors);
         goto error;
       }
       set_descriptors_array_on_structure (service, QUARK_DESCRIPTORS,
@@ -2303,11 +2311,10 @@ mpegts_packetizer_parse_eit (MpegTSPacketizer2 * packetizer,
         g_array_free (component_descriptors, TRUE);
       }
 
-      descriptors = g_value_array_new (mpegdescriptor.n_desc);
-      if (!mpegts_packetizer_parse_descriptors (packetizer,
-              &data, data + descriptors_loop_length, descriptors)) {
+      descriptors = mpegts_packetizer_parse_descriptors (packetizer,
+          &data, data + descriptors_loop_length);
+      if (!descriptors) {
         gst_structure_free (event);
-        g_value_array_free (descriptors);
         goto error;
       }
       set_descriptors_array_on_structure (event, QUARK_DESCRIPTORS,
@@ -2420,11 +2427,9 @@ mpegts_packetizer_parse_tot (MpegTSPacketizer2 * packetizer,
 
   desc_len = ((*data++) & 0xf) << 8;
   desc_len |= *data++;
-  descriptors = g_value_array_new (0);
-
-  if (!mpegts_packetizer_parse_descriptors (packetizer, &data, data + desc_len,
-          descriptors)) {
-    g_value_array_free (descriptors);
+  descriptors =
+      mpegts_packetizer_parse_descriptors (packetizer, &data, data + desc_len);
+  if (!descriptors) {
     gst_structure_free (tot);
     return NULL;
   }