dashdemux: Keep track of the PTS, not the SIDX index position between representations

There is no guarantee that the index positions are the same between
representations, and assuming this easily causes us to get into invalid
index positions.

ext/dash/gstdashdemux.c

@@ -1134,7 +1134,9 @@ gst_dash_demux_stream_update_fragment_info (GstAdaptiveDemuxStream * stream)
     gst_dash_demux_stream_update_headers_info (stream);
     dashstream->sidx_base_offset = stream->fragment.index_range_end + 1;
     /* sidx entries may not be available in here */
-    if (dashstream->sidx_index != 0 && SIDX (dashstream)->entries) {
+    if (dashstream->sidx_position != 0
+        && dashstream->sidx_position != GST_CLOCK_TIME_NONE
+        && SIDX (dashstream)->entries) {
       /* request only the index to be downloaded as we need to reposition the
        * stream to a subsegment */
       return GST_FLOW_OK;
@@ -1204,7 +1206,9 @@ gst_dash_demux_stream_update_fragment_info (GstAdaptiveDemuxStream * stream)
     stream->fragment.uri = fragment.uri;
     /* If mpd does not specify indexRange (i.e., null index_uri),
      * sidx entries may not be available until download it */
-    if (isombff && dashstream->sidx_index != 0 && SIDX (dashstream)->entries) {
+    if (isombff && dashstream->sidx_position != 0
+        && dashstream->sidx_position != GST_CLOCK_TIME_NONE
+        && SIDX (dashstream)->entries) {
       GstSidxBoxEntry *entry = SIDX_CURRENT_ENTRY (dashstream);
       stream->fragment.range_start =
           dashstream->sidx_base_offset + entry->offset;
@@ -1292,13 +1296,14 @@ gst_dash_demux_stream_sidx_seek (GstDashDemuxStream * dashstream,
   }
 
   sidx->entry_index = idx;
-  dashstream->sidx_index = idx;
+  if (idx == sidx->entries_count)
+    dashstream->sidx_position =
+        sidx->entries[idx - 1].pts + sidx->entries[idx - 1].duration;
+  else
+    dashstream->sidx_position = sidx->entries[idx].pts;
 
   if (final_ts) {
-    if (idx == sidx->entries_count)
+    *final_ts = dashstream->sidx_position;
-      *final_ts = sidx->entries[idx].pts + sidx->entries[idx].duration;
-    else
-      *final_ts = sidx->entries[idx].pts;
   }
 }
 
@@ -1332,6 +1337,7 @@ gst_dash_demux_stream_seek (GstAdaptiveDemuxStream * stream, gboolean forward,
       gst_isoff_sidx_parser_clear (&dashstream->sidx_parser);
       gst_isoff_sidx_parser_init (&dashstream->sidx_parser);
       dashstream->sidx_base_offset = 0;
+      dashstream->sidx_position = GST_CLOCK_TIME_NONE;
       if (dashstream->sidx_adapter)
         gst_adapter_clear (dashstream->sidx_adapter);
     }
@@ -1434,16 +1440,24 @@ gst_dash_demux_stream_advance_subfragment (GstAdaptiveDemuxStream * stream)
 
   if (dashstream->sidx_parser.status == GST_ISOFF_SIDX_PARSER_FINISHED) {
     if (stream->demux->segment.rate > 0.0) {
-      sidx->entry_index++;
+      gint idx = ++sidx->entry_index;
-      if (sidx->entry_index < sidx->entries_count) {
+      if (idx < sidx->entries_count) {
         fragment_finished = FALSE;
       }
-      dashstream->sidx_index++;
+
+      if (idx == sidx->entries_count)
+        dashstream->sidx_position =
+            sidx->entries[idx - 1].pts + sidx->entries[idx - 1].duration;
+      else
+        dashstream->sidx_position = sidx->entries[idx].pts;
     } else {
-      sidx->entry_index--;
+      gint idx = --sidx->entry_index;
-      dashstream->sidx_index--;
+
-      if (sidx->entry_index >= 0) {
+      if (idx >= 0) {
         fragment_finished = FALSE;
+        dashstream->sidx_position = sidx->entries[idx].pts;
+      } else {
+        dashstream->sidx_position = GST_CLOCK_TIME_NONE;
       }
     }
   }
@@ -1485,6 +1499,8 @@ gst_dash_demux_clear_pending_stream_data (GstDashDemux * dashdemux,
   gst_isoff_sidx_parser_init (&dashstream->sidx_parser);
   if (dashstream->sidx_adapter)
     gst_adapter_clear (dashstream->sidx_adapter);
+  dashstream->sidx_base_offset = 0;
+  dashstream->sidx_position = GST_CLOCK_TIME_NONE;
 
   /* Reset ISOBMFF box parsing state */
   if (dashstream->isobmff_adapter)
@@ -1542,7 +1558,7 @@ gst_dash_demux_stream_advance_fragment (GstAdaptiveDemuxStream * stream)
   gst_isoff_sidx_parser_clear (&dashstream->sidx_parser);
   gst_isoff_sidx_parser_init (&dashstream->sidx_parser);
   dashstream->sidx_base_offset = 0;
-  dashstream->sidx_index = 0;
+  dashstream->sidx_position = GST_CLOCK_TIME_NONE;
   if (dashstream->sidx_adapter)
     gst_adapter_clear (dashstream->sidx_adapter);
 
@@ -1619,13 +1635,25 @@ gst_dash_demux_stream_select_bitrate (GstAdaptiveDemuxStream * stream,
   }
 
   if (ret) {
-    gst_dash_demux_clear_pending_stream_data (demux, dashstream);
+    if (gst_mpd_client_has_isoff_ondemand_profile (demux->client)
-
+        && SIDX (dashstream)->entries) {
-    if (gst_mpd_client_has_isoff_ondemand_profile (demux->client)) {
       /* store our current position to change to the same one in a different
        * representation if needed */
-      dashstream->sidx_index = SIDX (dashstream)->entry_index;
+      if (SIDX (dashstream)->entry_index < SIDX (dashstream)->entries_count)
+        dashstream->sidx_position = SIDX_CURRENT_ENTRY (dashstream)->pts;
+      else if (SIDX (dashstream)->entry_index >=
+          SIDX (dashstream)->entries_count)
+        dashstream->sidx_position =
+            SIDX_ENTRY (dashstream,
+            SIDX (dashstream)->entries_count - 1)->pts + SIDX_ENTRY (dashstream,
+            SIDX (dashstream)->entries_count - 1)->duration;
+      else
+        dashstream->sidx_position = GST_CLOCK_TIME_NONE;
+    } else {
+      dashstream->sidx_position = GST_CLOCK_TIME_NONE;
     }
+
+    gst_dash_demux_clear_pending_stream_data (demux, dashstream);
   }
 
 end:
@@ -2254,7 +2282,23 @@ gst_dash_demux_parse_isobmff (GstAdaptiveDemux * demux,
           /* push buffer up to sidx box, and do pending stream seek  */
           break;
         } else {
-          SIDX (dash_stream)->entry_index = dash_stream->sidx_index;
+          gint idx = 0;
+
+          if (dash_stream->sidx_position == GST_CLOCK_TIME_NONE) {
+            idx = 0;
+          } else {
+            gint i;
+
+            /* Set sidx index to the highest entry that is smaller than our
+             * remembered position */
+            for (i = 0; i < SIDX (dash_stream)->entries_count; i++) {
+              idx = i;
+              if (SIDX_ENTRY (dash_stream, i)->pts + SIDX_ENTRY (dash_stream,
+                      i)->duration > dash_stream->sidx_position)
+                break;
+            }
+          }
+          SIDX (dash_stream)->entry_index = idx;
         }
       }
     } else {
@@ -2714,7 +2758,23 @@ gst_dash_demux_data_received (GstAdaptiveDemux * demux,
                 NULL);
             dash_stream->pending_seek_ts = GST_CLOCK_TIME_NONE;
           } else {
-            SIDX (dash_stream)->entry_index = dash_stream->sidx_index;
+            gint idx = 0;
+
+            if (dash_stream->sidx_position == GST_CLOCK_TIME_NONE) {
+              idx = 0;
+            } else {
+              gint i;
+
+              /* Set sidx index to the highest entry that is smaller than our
+               * remembered position */
+              for (i = 0; i < SIDX (dash_stream)->entries_count; i++) {
+                idx = i;
+                if (SIDX_ENTRY (dash_stream, i)->pts + SIDX_ENTRY (dash_stream,
+                        i)->duration > dash_stream->sidx_position)
+                  break;
+              }
+            }
+            SIDX (dash_stream)->entry_index = idx;
           }
         } else if (consumed < available) {
           GstBuffer *pending;

ext/dash/gstdashdemux.h

@@ -69,7 +69,7 @@ struct _GstDashDemuxStream
   /* index parsing */
   GstAdapter *sidx_adapter;
   GstSidxParser sidx_parser;
-  gint sidx_index;
+  GstClockTime sidx_position;
   gint64 sidx_base_offset;
   GstClockTime pending_seek_ts;
   /* sidx offset tracking */