h264parse: Properly handle 4 bytes start code

This will stop stripping four bytes start code. This was fixed and broken
again as it was causing the a timestamp shift. We now call
gst_base_parse_set_ts_at_offset() with the offset of the first NAL to ensure
that fixing a moderatly broken input stream won't affect the timestamps. We
also fixes the unit test, removing a comment about the stripping behaviour not
being correct.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1251>

1 files changed, 4 insertions, 21 deletions

diff --git a/gst/videoparsers/gsth264parse.c b/gst/videoparsers/gsth264parse.c
index 6a2c3d388..8f1215196 100644
--- a/gst/videoparsers/gsth264parse.c
+++ b/gst/videoparsers/gsth264parse.c
@@ -1315,7 +1315,6 @@ gst_h264_parse_handle_frame (GstBaseParse * parse,
   GstH264NalUnit nalu;
   GstH264ParserResult pres;
   gint framesize;
-  GstFlowReturn ret;
 
   if (G_UNLIKELY (GST_BUFFER_FLAG_IS_SET (frame->buffer,
               GST_BUFFER_FLAG_DISCONT))) {
@@ -1380,22 +1379,6 @@ gst_h264_parse_handle_frame (GstBaseParse * parse,
     switch (pres) {
       case GST_H264_PARSER_OK:
         if (nalu.sc_offset > 0) {
-          int i;
-          gboolean is_filler_data = TRUE;
-          /* Handle filler data */
-          for (i = 0; i < nalu.sc_offset; i++) {
-            if (data[i] != 0x00) {
-              is_filler_data = FALSE;
-              break;
-            }
-          }
-          if (is_filler_data) {
-            GST_DEBUG_OBJECT (parse, "Dropping filler data %d", nalu.sc_offset);
-            frame->flags |= GST_BASE_PARSE_FRAME_FLAG_DROP;
-            gst_buffer_unmap (buffer, &map);
-            ret = gst_base_parse_finish_frame (parse, frame, nalu.sc_offset);
-            goto drop;
-          }
           *skipsize = nalu.sc_offset;
           goto skip;
         }
@@ -1410,6 +1393,10 @@ gst_h264_parse_handle_frame (GstBaseParse * parse,
             ("Error parsing H.264 stream"), ("Invalid H.264 stream"));
         goto invalid_stream;
     }
+
+    /* Ensure we use the TS of the first NAL. This avoids broken timestamp in
+     * the case of a miss-placed filler byte. */
+    gst_base_parse_set_ts_at_offset (parse, nalu.offset);
   }
 
   while (TRUE) {
@@ -1576,10 +1563,6 @@ out:
   gst_buffer_unmap (buffer, &map);
   return GST_FLOW_OK;
 
-drop:
-  GST_DEBUG_OBJECT (h264parse, "Dropped data");
-  return ret;
-
 skip:
   GST_DEBUG_OBJECT (h264parse, "skipping %d", *skipsize);
   /* If we are collecting access units, we need to preserve the initial