hlsdemux2: Print playlist age in debug output

Store the timestamp when playlists are updated, and add some debug output to the
update_fragment_info that estimates how far from the live edge the fragment
currently is

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3883>

subprojects/gst-plugins-good/ext/adaptivedemux2/hls/gsthlsdemux.c

@@ -2308,6 +2308,8 @@ gst_hls_demux_stream_update_media_playlist (GstHLSDemux * demux,
     GST_WARNING_OBJECT (stream, "Could not get playlist '%s'", *uri);
     return GST_FLOW_ERROR;
   }
+  stream->playlist_last_update_time =
+      gst_adaptive_demux2_get_monotonic_time (GST_ADAPTIVE_DEMUX (demux));
 
   /* Check if a redirect happened */
   if (g_strcmp0 (*uri, new_playlist->uri)) {
@@ -2363,7 +2365,8 @@ gst_hls_demux_stream_update_media_playlist (GstHLSDemux * demux,
         gst_hls_media_playlist_sync_to_segment (new_playlist,
         stream->current_segment);
 
-    /* FIXME: Handle LL-HLS partial segment sync */
+    /* Handle LL-HLS partial segment sync by checking our partial segment
+     * still makes sense */
     if (stream->in_partial_segments && new_segment) {
       /* We must be either playing the trailing open-ended partial segment,
        * or if we're playing partials from a complete segment, check that we
@@ -2529,10 +2532,20 @@ gst_hls_demux_stream_update_fragment_info (GstAdaptiveDemux2Stream * stream)
     if (ret != GST_FLOW_OK)
       return ret;
   }
-
+#ifndef GST_DISABLE_GST_DEBUG
+  GstClockTimeDiff live_edge_dist =
+      GST_CLOCK_TIME_IS_VALID (stream->current_position) ?
+      gst_hls_media_playlist_get_end_stream_time (hlsdemux_stream->playlist) -
+      stream->current_position : GST_CLOCK_TIME_NONE;
+  GstClockTime playlist_age =
+      gst_adaptive_demux2_get_monotonic_time (GST_ADAPTIVE_DEMUX (demux)) -
+      hlsdemux_stream->playlist_last_update_time;
   GST_DEBUG_OBJECT (stream,
-      "Updating fragment information, current_position:%" GST_TIME_FORMAT,
-      GST_TIME_ARGS (stream->current_position));
+      "Updating fragment information, current_position:%" GST_TIME_FORMAT
+      " which is %" GST_STIME_FORMAT " from live edge. Playlist age %"
+      GST_TIME_FORMAT, GST_TIME_ARGS (stream->current_position),
+      GST_STIME_ARGS (live_edge_dist), GST_TIME_ARGS (playlist_age));
+#endif
 
   /* Find the current segment if we don't already have it */
   if (hlsdemux_stream->current_segment == NULL) {

subprojects/gst-plugins-good/ext/adaptivedemux2/hls/gsthlsdemux.h

@@ -111,6 +111,7 @@ struct _GstHLSDemuxStream
 
   /* Whether the underlying playlist was fetched on creation */
   gboolean playlist_fetched;
+  GstClockTime playlist_last_update_time;
 
   /* The media playlist currently used */
   GstHLSMediaPlaylist *playlist;

subprojects/gst-plugins-good/ext/adaptivedemux2/hls/m3u8.c

@@ -2146,6 +2146,18 @@ out:
   return file;
 }
 
+GstClockTime
+gst_hls_media_playlist_get_end_stream_time (GstHLSMediaPlaylist * m3u8)
+{
+  if (m3u8->segments->len == 0)
+    return GST_CLOCK_TIME_NONE;
+
+  GstM3U8MediaSegment *last =
+      g_ptr_array_index (m3u8->segments, m3u8->segments->len - 1);
+
+  return last->stream_time + last->duration;
+}
+
 GstClockTime
 gst_hls_media_playlist_get_duration (GstHLSMediaPlaylist * m3u8)
 {

subprojects/gst-plugins-good/ext/adaptivedemux2/hls/m3u8.h

@@ -294,6 +294,9 @@ gboolean
 gst_hls_media_playlist_get_starting_segment (GstHLSMediaPlaylist *self, gboolean low_latency,
     GstM3U8SeekResult *seek_result);
 
+GstClockTime
+gst_hls_media_playlist_get_end_stream_time  (GstHLSMediaPlaylist * m3u8);
+
 GstClockTime
 gst_hls_media_playlist_get_duration         (GstHLSMediaPlaylist * m3u8);