dashdemux: implement snap seek handling

Handle snap seeking at the stream_seek method and let superclass
do the rest to support snap seeking

https://bugzilla.gnome.org/show_bug.cgi?id=759158

ext/dash/gstdashdemux.c

@@ -1067,7 +1067,8 @@ gst_dash_demux_index_entry_search (GstSidxBoxEntry * entry, GstClockTime * ts,
 
 static void
 gst_dash_demux_stream_sidx_seek (GstDashDemuxStream * dashstream,
-    GstSeekFlags flags, GstClockTime ts, GstClockTime * final_ts)
+    gboolean forward, GstSeekFlags flags, GstClockTime ts,
+    GstClockTime * final_ts)
 {
   GstSidxBox *sidx = SIDX (dashstream);
   GstSidxBoxEntry *entry;
@@ -1077,13 +1078,34 @@ gst_dash_demux_stream_sidx_seek (GstDashDemuxStream * dashstream,
   if (sidx->entries[idx - 1].pts + sidx->entries[idx - 1].duration < ts) {
     dashstream->sidx_current_remaining = 0;
   } else {
+    GstSearchMode mode = GST_SEARCH_MODE_BEFORE;
+
+    if ((flags & GST_SEEK_FLAG_SNAP_NEAREST) == GST_SEEK_FLAG_SNAP_NEAREST) {
+      mode = GST_SEARCH_MODE_BEFORE;
+    } else if ((forward && (flags & GST_SEEK_FLAG_SNAP_AFTER)) ||
+        (!forward && (flags & GST_SEEK_FLAG_SNAP_BEFORE))) {
+      mode = GST_SEARCH_MODE_AFTER;
+    } else {
+      mode = GST_SEARCH_MODE_BEFORE;
+    }
+
     entry =
         gst_util_array_binary_search (sidx->entries, sidx->entries_count,
         sizeof (GstSidxBoxEntry),
-        (GCompareDataFunc) gst_dash_demux_index_entry_search,
+        (GCompareDataFunc) gst_dash_demux_index_entry_search, mode, &ts, NULL);
-        GST_SEARCH_MODE_BEFORE, &ts, NULL);
 
     idx = entry - sidx->entries;
+
+    /* FIXME in reverse mode, if we are exactly at a fragment start it makes more
+     * sense to start from the end of the previous fragment */
+    /* FIXME we should have a GST_SEARCH_MODE_NEAREST */
+    if ((flags & GST_SEEK_FLAG_SNAP_NEAREST) == GST_SEEK_FLAG_SNAP_NEAREST &&
+        idx + 1 < sidx->entries_count) {
+      if (ABS (sidx->entries[idx + 1].pts - ts) <
+          ABS (sidx->entries[idx].pts - ts))
+        idx += 1;
+    }
+
     dashstream->sidx_current_remaining = sidx->entries[idx].size;
   }
 
@@ -1107,7 +1129,8 @@ gst_dash_demux_stream_seek (GstAdaptiveDemuxStream * stream, gboolean forward,
 
   if (gst_mpd_client_has_isoff_ondemand_profile (dashdemux->client)) {
     if (dashstream->sidx_parser.status == GST_ISOFF_SIDX_PARSER_FINISHED) {
-      gst_dash_demux_stream_sidx_seek (dashstream, flags, ts, final_ts);
+      gst_dash_demux_stream_sidx_seek (dashstream, forward, flags, ts,
+          final_ts);
     } else {
       /* no index yet, seek when we have it */
       /* FIXME - the final_ts won't be correct here */
@@ -1611,8 +1634,9 @@ gst_dash_demux_data_received (GstAdaptiveDemux * demux,
         if (dash_stream->sidx_parser.status == GST_ISOFF_SIDX_PARSER_FINISHED) {
           if (GST_CLOCK_TIME_IS_VALID (dash_stream->pending_seek_ts)) {
             /* FIXME, preserve seek flags */
-            gst_dash_demux_stream_sidx_seek (dash_stream, 0,
+            gst_dash_demux_stream_sidx_seek (dash_stream,
-                dash_stream->pending_seek_ts, NULL);
+                demux->segment.rate >= 0, 0, dash_stream->pending_seek_ts,
+                NULL);
             dash_stream->pending_seek_ts = GST_CLOCK_TIME_NONE;
           } else {
             SIDX (dash_stream)->entry_index = dash_stream->sidx_index;

ext/dash/gstmpdparser.c

@@ -4670,18 +4670,48 @@ gst_mpd_client_stream_seek (GstMpdClient * client, GstActiveStream * stream,
           stream->segments->len);
       in_segment = FALSE;
       if (segment->start <= ts) {
+        GstClockTime end_time;
+
         if (segment->repeat >= 0) {
-          in_segment =
+          end_time = segment->start + (segment->repeat + 1) * segment->duration;
-              ts < segment->start + (segment->repeat + 1) * segment->duration;
         } else {
-          GstClockTime end =
+          end_time =
               gst_mpdparser_get_segment_end_time (client, stream->segments,
               segment, index);
-          in_segment = ts < end;
         }
+
+        /* avoid downloading another fragment just for 1ns in reverse mode */
+        if (forward)
+          in_segment = ts < end_time;
+        else
+          in_segment = ts <= end_time;
+
         if (in_segment) {
           selectedChunk = segment;
           repeat_index = (ts - segment->start) / segment->duration;
+
+          /* At the end of a segment in reverse mode, start from the previous fragment */
+          if (!forward && repeat_index > 0
+              && ((ts - segment->start) % segment->duration == 0))
+            repeat_index--;
+
+          if ((flags & GST_SEEK_FLAG_SNAP_NEAREST) ==
+              GST_SEEK_FLAG_SNAP_NEAREST) {
+            /* FIXME implement this */
+          } else if ((forward && flags & GST_SEEK_FLAG_SNAP_AFTER) ||
+              (!forward && flags & GST_SEEK_FLAG_SNAP_BEFORE)) {
+
+            if (repeat_index + 1 < segment->repeat) {
+              repeat_index++;
+            } else {
+              repeat_index = 0;
+              if (index + 1 >= stream->segments->len) {
+                selectedChunk = NULL;
+              } else {
+                selectedChunk = g_ptr_array_index (stream->segments, index + 1);
+              }
+            }
+          }
           break;
         }
       }
@@ -4714,6 +4744,14 @@ gst_mpd_client_stream_seek (GstMpdClient * client, GstActiveStream * stream,
       ts = 0;
 
     index = ts / duration;
+
+    if ((flags & GST_SEEK_FLAG_SNAP_NEAREST) == GST_SEEK_FLAG_SNAP_NEAREST) {
+      /* FIXME implement this */
+    } else if ((forward && flags & GST_SEEK_FLAG_SNAP_AFTER) ||
+        (!forward && flags & GST_SEEK_FLAG_SNAP_BEFORE)) {
+      index++;
+    }
+
     if (segments_count > 0 && index >= segments_count) {
       stream->segment_index = segments_count;
       stream->segment_repeat_index = 0;