dashdemux: Fix segfault introduced by segment iteration refactoring (2105a310).

The functions to get the next fragment, next fragment timestamp and to advance
to the next fragment need to work differently when stream->segments is NULL.
Use logic similar to that introduced by commit 2105a310 to perform these
functions.

https://bugzilla.gnome.org/show_bug.cgi?id=749684

ext/dash/gstmpdparser.c

@@ -3580,15 +3580,26 @@ gst_mpd_client_get_next_fragment_timestamp (GstMpdClient * client,
   stream = g_list_nth_data (client->active_streams, stream_idx);
   g_return_val_if_fail (stream != NULL, 0);
 
-  GST_DEBUG ("Looking for fragment sequence chunk %d / %d",
+  if (stream->segments) {
-      stream->segment_index, stream->segments->len);
+    GST_DEBUG ("Looking for fragment sequence chunk %d / %d",
-  if (stream->segment_index >= stream->segments->len)
+        stream->segment_index, stream->segments->len);
-    return FALSE;
+    if (stream->segment_index >= stream->segments->len)
-  currentChunk = g_ptr_array_index (stream->segments, stream->segment_index);
+      return FALSE;
+    currentChunk = g_ptr_array_index (stream->segments, stream->segment_index);
 
-  *ts =
+    *ts =
-      currentChunk->start +
+        currentChunk->start +
-      (currentChunk->duration * stream->segment_repeat_index);
+        (currentChunk->duration * stream->segment_repeat_index);
+  } else {
+    GstClockTime duration =
+        gst_mpd_client_get_segment_duration (client, stream, NULL);
+    g_return_val_if_fail (stream->cur_seg_template->
+        MultSegBaseType->SegmentTimeline == NULL, FALSE);
+    if (!GST_CLOCK_TIME_IS_VALID (duration)) {
+      return FALSE;
+    }
+    *ts = stream->segment_index * duration;
+  }
 
   return TRUE;
 }
@@ -3624,43 +3635,22 @@ gst_mpd_client_get_next_fragment (GstMpdClient * client,
   g_return_val_if_fail (stream != NULL, FALSE);
   g_return_val_if_fail (stream->cur_representation != NULL, FALSE);
 
-  GST_DEBUG ("Looking for fragment sequence chunk %d / %d",
+  if (stream->segments) {
-      stream->segment_index, stream->segments->len);
+    GST_DEBUG ("Looking for fragment sequence chunk %d / %d",
-  if (stream->segment_index >= stream->segments->len)
+        stream->segment_index, stream->segments->len);
-    return FALSE;
+    if (stream->segment_index >= stream->segments->len)
-  currentChunk = g_ptr_array_index (stream->segments, stream->segment_index);
+      return FALSE;
-
+  } else {
-  GST_DEBUG ("currentChunk->SegmentURL = %p", currentChunk->SegmentURL);
+    GstClockTime duration = gst_mpd_client_get_segment_duration (client,
-  if (currentChunk->SegmentURL != NULL) {
+        stream, NULL);
-    mediaURL =
+    g_return_val_if_fail (stream->cur_seg_template->
-        g_strdup (gst_mpdparser_get_mediaURL (stream,
+        MultSegBaseType->SegmentTimeline == NULL, FALSE);
-            currentChunk->SegmentURL));
+    if (!GST_CLOCK_TIME_IS_VALID (duration)) {
-    indexURL = currentChunk->SegmentURL->index;
+      return FALSE;
-  } else if (stream->cur_seg_template != NULL) {
-    mediaURL =
-        gst_mpdparser_build_URL_from_template (stream->cur_seg_template->media,
-        stream->cur_representation->id,
-        currentChunk->number + stream->segment_repeat_index,
-        stream->cur_representation->bandwidth,
-        currentChunk->scale_start +
-        stream->segment_repeat_index * currentChunk->scale_duration);
-    if (stream->cur_seg_template->index) {
-      indexURL =
-          gst_mpdparser_build_URL_from_template (stream->
-          cur_seg_template->index, stream->cur_representation->id,
-          currentChunk->number + stream->segment_repeat_index,
-          stream->cur_representation->bandwidth,
-          currentChunk->scale_start +
-          stream->segment_repeat_index * currentChunk->scale_duration);
     }
+    fragment->duration = duration;
   }
-  GST_DEBUG ("mediaURL = %s", mediaURL);
-  GST_DEBUG ("indexURL = %s", indexURL);
 
-  fragment->timestamp =
-      currentChunk->start +
-      stream->segment_repeat_index * currentChunk->duration;
-  fragment->duration = currentChunk->duration;
   /* FIXME rework discont checking */
   /* fragment->discontinuity = segment_idx != currentChunk.number; */
   fragment->range_start = 0;
@@ -3668,18 +3658,77 @@ gst_mpd_client_get_next_fragment (GstMpdClient * client,
   fragment->index_uri = NULL;
   fragment->index_range_start = 0;
   fragment->index_range_end = -1;
-  if (currentChunk->SegmentURL) {
+
-    if (currentChunk->SegmentURL->mediaRange) {
+  if (stream->segments) {
-      fragment->range_start =
+    currentChunk = g_ptr_array_index (stream->segments, stream->segment_index);
-          currentChunk->SegmentURL->mediaRange->first_byte_pos;
+
-      fragment->range_end = currentChunk->SegmentURL->mediaRange->last_byte_pos;
+    GST_DEBUG ("currentChunk->SegmentURL = %p", currentChunk->SegmentURL);
+    if (currentChunk->SegmentURL != NULL) {
+      mediaURL =
+          g_strdup (gst_mpdparser_get_mediaURL (stream,
+              currentChunk->SegmentURL));
+      indexURL = currentChunk->SegmentURL->index;
+    } else if (stream->cur_seg_template != NULL) {
+      mediaURL =
+          gst_mpdparser_build_URL_from_template (stream->
+          cur_seg_template->media, stream->cur_representation->id,
+          currentChunk->number + stream->segment_repeat_index,
+          stream->cur_representation->bandwidth,
+          currentChunk->scale_start +
+          stream->segment_repeat_index * currentChunk->scale_duration);
+      if (stream->cur_seg_template->index) {
+        indexURL =
+            gst_mpdparser_build_URL_from_template (stream->
+            cur_seg_template->index, stream->cur_representation->id,
+            currentChunk->number + stream->segment_repeat_index,
+            stream->cur_representation->bandwidth,
+            currentChunk->scale_start +
+            stream->segment_repeat_index * currentChunk->scale_duration);
+      }
     }
-    if (currentChunk->SegmentURL->indexRange) {
+    GST_DEBUG ("mediaURL = %s", mediaURL);
-      fragment->index_range_start =
+    GST_DEBUG ("indexURL = %s", indexURL);
-          currentChunk->SegmentURL->indexRange->first_byte_pos;
+
-      fragment->index_range_end =
+    fragment->timestamp =
-          currentChunk->SegmentURL->indexRange->last_byte_pos;
+        currentChunk->start +
+        stream->segment_repeat_index * currentChunk->duration;
+    fragment->duration = currentChunk->duration;
+    if (currentChunk->SegmentURL) {
+      if (currentChunk->SegmentURL->mediaRange) {
+        fragment->range_start =
+            currentChunk->SegmentURL->mediaRange->first_byte_pos;
+        fragment->range_end =
+            currentChunk->SegmentURL->mediaRange->last_byte_pos;
+      }
+      if (currentChunk->SegmentURL->indexRange) {
+        fragment->index_range_start =
+            currentChunk->SegmentURL->indexRange->first_byte_pos;
+        fragment->index_range_end =
+            currentChunk->SegmentURL->indexRange->last_byte_pos;
+      }
     }
+  } else {
+    if (stream->cur_seg_template != NULL) {
+      mediaURL =
+          gst_mpdparser_build_URL_from_template (stream->
+          cur_seg_template->media, stream->cur_representation->id,
+          stream->segment_index, stream->cur_representation->bandwidth,
+          stream->segment_index * fragment->duration);
+      if (stream->cur_seg_template->index) {
+        indexURL =
+            gst_mpdparser_build_URL_from_template (stream->
+            cur_seg_template->index, stream->cur_representation->id,
+            stream->segment_index, stream->cur_representation->bandwidth,
+            stream->segment_index * fragment->duration);
+      }
+    } else {
+      return FALSE;
+    }
+
+    GST_DEBUG ("mediaURL = %s", mediaURL);
+    GST_DEBUG ("indexURL = %s", indexURL);
+
+    fragment->timestamp = stream->segment_index * fragment->duration;
   }
 
   base_url = gst_uri_from_string (stream->baseURL);
@@ -3725,6 +3774,8 @@ gst_mpd_client_has_next_segment (GstMpdClient * client,
     GstActiveStream * stream, gboolean forward)
 {
   if (forward) {
+    if (stream->segments == NULL)
+      return TRUE;
     if (stream->segment_index >= stream->segments->len)
       return FALSE;
   } else {
@@ -3740,13 +3791,22 @@ gst_mpd_client_advance_segment (GstMpdClient * client, GstActiveStream * stream,
     gboolean forward)
 {
   GstMediaSegment *segment;
+  guint segments_count = gst_mpd_client_get_segments_counts (stream);
 
   GST_DEBUG ("Advancing segment. Current: %d / %d r:%d", stream->segment_index,
-      stream->segments->len, stream->segment_repeat_index);
+      segments_count, stream->segment_repeat_index);
 
   /* handle special cases first */
   if (forward) {
-    if (stream->segment_index >= stream->segments->len)
+    if (stream->segments == NULL) {
+      if (stream->segment_index < 0)
+        stream->segment_index = 0;
+      else
+        stream->segment_index++;
+      return GST_FLOW_OK;
+    }
+
+    if (stream->segment_index >= segments_count)
       return GST_FLOW_EOS;
 
     /* special case for when playback direction is reverted right at *
@@ -3756,13 +3816,19 @@ gst_mpd_client_advance_segment (GstMpdClient * client, GstActiveStream * stream,
       return GST_FLOW_OK;
     }
   } else {
-    if (stream->segment_index < 0)
+    if (stream->segments == NULL)
+      stream->segment_index--;
+    if (stream->segment_index < 0) {
+      stream->segment_index = -1;
       return GST_FLOW_EOS;
+    }
+    if (stream->segments == NULL)
+      return GST_FLOW_OK;
 
     /* special case for when playback direction is reverted right at *
      * the end of the segment list */
-    if (stream->segment_index >= stream->segments->len) {
+    if (stream->segment_index >= segments_count) {
-      stream->segment_index = stream->segments->len - 1;
+      stream->segment_index = segments_count - 1;
       segment = g_ptr_array_index (stream->segments, stream->segment_index);
       stream->segment_repeat_index = segment->repeat;
       return GST_FLOW_OK;