mpegvideoparse: fix timestamp generation

Use information from the gop header and picture
header to calculate the picture timestamp. (time_code
and temporal_reference) and adapt to upstream timestamps if
provided.

https://bugzilla.gnome.org/show_bug.cgi?id=632222

gst/mpegvideoparse/mpegpacketiser.c

@@ -636,7 +636,9 @@ mpeg_util_parse_picture_hdr (MPEGPictureHdr * hdr, guint8 * data, guint8 * end)
   /* Skip the start code */
   data += 4;
 
+  hdr->temp_ref = (data[0] << 2) | (data[1] >> 6);
   hdr->pic_type = (data[1] >> 3) & 0x07;
+
   if (hdr->pic_type == 0 || hdr->pic_type > 4)
     return FALSE;               /* Corrupted picture packet */
 

gst/mpegvideoparse/mpegpacketiser.h

@@ -86,6 +86,7 @@ struct MPEGSeqHdr
 
 struct MPEGPictureHdr
 {
+  guint16 temp_ref;
   guint8 pic_type;
 };
 

gst/mpegvideoparse/mpegvideoparse.c

@@ -92,6 +92,10 @@ gst_mpegvideoparse_change_state (GstElement * element,
 
 static void mpv_send_pending_segs (MpegVideoParse * mpegvideoparse);
 static void mpv_clear_pending_segs (MpegVideoParse * mpegvideoparse);
+static GstClockTime mpegvideoparse_get_timestamp_from_reference (MPEGSeqHdr *
+    seq_hdr, GstClockTime ref_ts, gint32 ref);
+static GstClockTime mpegvideoparse_get_time_code (guint8 * cur,
+    MPEGSeqHdr * seq_hdr);
 
 static GstElementClass *parent_class = NULL;
 
@@ -163,6 +167,9 @@ mpv_parse_reset (MpegVideoParse * mpegvideoparse)
   mpegvideoparse->seq_hdr.fps_n = mpegvideoparse->seq_hdr.par_w = 0;
   mpegvideoparse->seq_hdr.fps_d = mpegvideoparse->seq_hdr.par_h = 1;
 
+  mpegvideoparse->ref_ts = GST_CLOCK_TIME_NONE;
+  mpegvideoparse->base_time_code = GST_CLOCK_TIME_NONE;
+
   mpv_clear_pending_segs (mpegvideoparse);
 }
 
@@ -404,6 +411,30 @@ picture_type_name (guint8 pct)
 }
 #endif /* GST_DISABLE_GST_DEBUG */
 
+static GstClockTime
+mpegvideoparse_get_timestamp_from_reference (MPEGSeqHdr * seq_hdr,
+    GstClockTime ref_ts, gint32 ref)
+{
+
+  if (ref < 0) {
+    GstClockTime duration;
+
+    duration = gst_util_uint64_scale_int (ref * GST_SECOND * -1,
+        seq_hdr->fps_d, seq_hdr->fps_n);
+
+    if (duration > ref_ts)
+      return ref_ts;
+    else
+      return ref_ts - duration;
+  }
+
+  if (ref == 0)
+    return ref_ts;
+
+  return ref_ts + gst_util_uint64_scale_int (ref * GST_SECOND,
+      seq_hdr->fps_d, seq_hdr->fps_n);
+}
+
 static gboolean
 mpegvideoparse_handle_picture (MpegVideoParse * mpegvideoparse, GstBuffer * buf)
 {
@@ -432,8 +463,43 @@ mpegvideoparse_handle_picture (MpegVideoParse * mpegvideoparse, GstBuffer * buf)
 
       GST_LOG_OBJECT (mpegvideoparse, "Picture type is %s",
           picture_type_name (hdr.pic_type));
-      /* FIXME: Can use the picture type and number of fields to track a
+
-       * timestamp */
+      if (GST_BUFFER_TIMESTAMP (buf) == GST_CLOCK_TIME_NONE) {
+        if (mpegvideoparse->ref_ts != GST_CLOCK_TIME_NONE) {
+          GST_BUFFER_TIMESTAMP (buf) =
+              mpegvideoparse_get_timestamp_from_reference
+              (&mpegvideoparse->seq_hdr, mpegvideoparse->ref_ts,
+              hdr.temp_ref - mpegvideoparse->temp_ref);
+        }
+      } else {
+        /* we got a timestamp from upstream, use this timestamp as our reference now */
+        mpegvideoparse->ref_ts = GST_BUFFER_TIMESTAMP (buf);
+        mpegvideoparse->temp_ref = hdr.temp_ref;
+      }
+
+      GST_DEBUG_OBJECT (mpegvideoparse,
+          "Picture timestamp %" GST_TIME_FORMAT,
+          GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (buf)));
+    } else if (cur[0] == MPEG_PACKET_GOP) {
+      if (GST_BUFFER_TIMESTAMP (buf) != GST_CLOCK_TIME_NONE) {
+        mpegvideoparse->base_time_code =
+            mpegvideoparse_get_time_code (cur,
+            &mpegvideoparse->seq_hdr) - GST_BUFFER_TIMESTAMP (buf);
+        mpegvideoparse->ref_ts = GST_BUFFER_TIMESTAMP (buf);
+        mpegvideoparse->temp_ref = 0;
+      } else {
+        if (mpegvideoparse->base_time_code == GST_CLOCK_TIME_NONE) {
+          mpegvideoparse->base_time_code =
+              mpegvideoparse_get_time_code (cur, &mpegvideoparse->seq_hdr);
+          mpegvideoparse->ref_ts = 0;
+          mpegvideoparse->temp_ref = 0;
+        } else {
+          mpegvideoparse->ref_ts =
+              mpegvideoparse_get_time_code (cur,
+              &mpegvideoparse->seq_hdr) - mpegvideoparse->base_time_code;
+          mpegvideoparse->temp_ref = 0;
+        }
+      }
     }
     cur = mpeg_util_find_start_code (&sync_word, cur, end);
   }
@@ -441,11 +507,10 @@ mpegvideoparse_handle_picture (MpegVideoParse * mpegvideoparse, GstBuffer * buf)
   return TRUE;
 }
 
-#if 0
+static GstClockTime
-static guint64
+mpegvideoparse_get_time_code (guint8 * cur, MPEGSeqHdr * seq_hdr)
-gst_mpegvideoparse_time_code (guchar * gop, MPEGSeqHdr * seq_hdr)
 {
-  guint32 data = GST_READ_UINT32_BE (gop);
+  guint32 data = GST_READ_UINT32_BE (cur + 1);
   guint64 seconds;
   guint8 frames;
 
@@ -458,7 +523,6 @@ gst_mpegvideoparse_time_code (guchar * gop, MPEGSeqHdr * seq_hdr)
   return seconds * GST_SECOND + gst_util_uint64_scale_int (frames * GST_SECOND,
       seq_hdr->fps_d, seq_hdr->fps_n);
 }
-#endif
 
 static void
 gst_mpegvideoparse_flush (MpegVideoParse * mpegvideoparse)

gst/mpegvideoparse/mpegvideoparse.h

@@ -49,6 +49,11 @@ struct _MpegVideoParse {
   gint64 next_offset;
   gboolean need_discont;
 
+  /* Timestamp calculation */
+  GstClockTime ref_ts;
+  guint16 temp_ref;
+  GstClockTime base_time_code;
+
   /* Info from the Sequence Header */
   MPEGSeqHdr seq_hdr;
   GstBuffer *seq_hdr_buf;