h264parse, h265parse: Fix timecode parsing

The scaling factor for nFrame part should be "(1 + nuit_field_based_flag) / 2"

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5254>

subprojects/gst-plugins-bad/gst/videoparsers/gsth264parse.c

@@ -3208,6 +3208,7 @@ gst_h264_parse_pre_push_frame (GstBaseParse * parse, GstBaseParseFrame * frame)
   GstEvent *event;
   GstBuffer *parse_buffer = NULL;
   gboolean is_interlaced = FALSE;
+  GstH264SPS *sps;
 
   h264parse = GST_H264_PARSE (parse);
 
@@ -3369,8 +3370,15 @@ gst_h264_parse_pre_push_frame (GstBaseParse * parse, GstBaseParseFrame * frame)
     parse_buffer = frame->buffer = gst_buffer_make_writable (frame->buffer);
   }
 
-  if (!gst_buffer_get_video_time_code_meta (parse_buffer)) {
+  sps = h264parse->nalparser->last_sps;
+  if (sps && sps->vui_parameters_present_flag &&
+      sps->vui_parameters.timing_info_present_flag &&
+      sps->vui_parameters.time_scale > 0 &&
+      sps->vui_parameters.num_units_in_tick > 0 &&
+      h264parse->parsed_fps_n > 0 && h264parse->parsed_fps_d > 0 &&
+      !gst_buffer_get_video_time_code_meta (parse_buffer)) {
     guint i = 0;
+    GstH264VUIParams *vui = &sps->vui_parameters;
 
     for (i = 0; i < 3 && h264parse->num_clock_timestamp; i++) {
       GstH264ClockTimestamp *tim =
@@ -3378,6 +3386,7 @@ gst_h264_parse_pre_push_frame (GstBaseParse * parse, GstBaseParseFrame * frame)
       gint field_count = -1;
       guint n_frames;
       GstVideoTimeCodeFlags flags = 0;
+      guint64 scale_n, scale_d;
 
       if (!h264parse->pic_timing_sei.clock_timestamp_flag[i])
         continue;
@@ -3424,9 +3433,37 @@ gst_h264_parse_pre_push_frame (GstBaseParse * parse, GstBaseParseFrame * frame)
         is_interlaced = TRUE;
       }
 
-      n_frames =
+      /* Equation D-1 (without and tOffset)
-          gst_util_uint64_scale_int (tim->n_frames, 1,
+       *
-          2 - tim->nuit_field_based_flag);
+       * clockTimestamp = ( ( hH * 60 + mM ) * 60 + sS ) * time_scale +
+       *                  nFrames * ( num_units_in_tick * ( 1 + nuit_field_based_flag ) )
+       * => timestamp = clockTimestamp / time_scale
+       *
+       * <taking only frame part>
+       * timestamp = nFrames * ( num_units_in_tick * ( 1 + nuit_field_based_flag ) ) / time_scale
+       *
+       * <timecode's timestamp of frame part>
+       * timecode_timestamp = n_frames * fps_d / fps_n
+       *
+       * <Scaling Equation>
+       * n_frames = nFrames * ( num_units_in_tick * ( 1 + nuit_field_based_flag ) ) / time_scale
+       *            * fps_n / fps_d
+       *
+       *                       fps_n * ( num_units_in_tick * ( 1 + nuit_field_based_flag ) )
+       *          = nFrames * --------------------------------------------------------------
+       *                       fps_d * time_scale
+       *
+       * NOTE: "time_scale / num_units_in_tick" value is expected field rate
+       * (i.e., framerate = time_scale / (2 * num_units_in_tick)), so the above
+       * equation can be simplified if the bitstream is conveying field rate
+       * using time_scale / num_units_in_tick
+       * => "n_frames = nFrames * (1 + nuit_field_based_flag) / 2".
+       */
+      scale_n = h264parse->parsed_fps_n * vui->num_units_in_tick
+          * (1 + tim->nuit_field_based_flag);
+      scale_d = h264parse->parsed_fps_d * vui->time_scale;
+
+      n_frames = gst_util_uint64_scale (tim->n_frames, scale_n, scale_d);
 
       GST_LOG_OBJECT (h264parse,
           "Add time code meta %02u:%02u:%02u:%02u",

subprojects/gst-plugins-bad/gst/videoparsers/gsth265parse.c

@@ -2910,6 +2910,7 @@ gst_h265_parse_pre_push_frame (GstBaseParse * parse, GstBaseParseFrame * frame)
   GstBuffer *buffer;
   GstEvent *event;
   GstBuffer *parse_buffer = NULL;
+  GstH265SPS *sps;
 
   h265parse = GST_H265_PARSE (parse);
 
@@ -3043,13 +3044,20 @@ gst_h265_parse_pre_push_frame (GstBaseParse * parse, GstBaseParseFrame * frame)
       break;
   }
 
-  {
+  sps = h265parse->nalparser->last_sps;
+  if (sps && sps->vui_parameters_present_flag &&
+      sps->vui_params.timing_info_present_flag &&
+      sps->vui_params.time_scale > 0 &&
+      sps->vui_params.num_units_in_tick > 0 &&
+      !gst_buffer_get_video_time_code_meta (parse_buffer)) {
     guint i = 0;
+    GstH265VUIParams *vui = &sps->vui_params;
 
     for (i = 0; i < h265parse->time_code.num_clock_ts; i++) {
       gint field_count = -1;
       guint n_frames;
       GstVideoTimeCodeFlags flags = 0;
+      guint64 scale_n, scale_d;
 
       if (!h265parse->time_code.clock_timestamp_flag[i])
         break;
@@ -3100,9 +3108,33 @@ gst_h265_parse_pre_push_frame (GstBaseParse * parse, GstBaseParseFrame * frame)
       if (h265parse->sei_pic_struct != GST_H265_SEI_PIC_STRUCT_FRAME)
         flags |= GST_VIDEO_TIME_CODE_FLAGS_INTERLACED;
 
+      /* Equation D-26 (without and tOffset)
+       *
+       * clockTimestamp[i] = ( ( hH * 60 + mM ) * 60 + sS ) * vui_time_scale +
+       *                  nFrames * ( vui_num_units_in_tick * ( 1 + unit_field_based_flag[i] ) )
+       * => timestamp = clockTimestamp / time_scale
+       *
+       * <taking only frame part>
+       * timestamp = nFrames * ( vui_num_units_in_tick * ( 1 + unit_field_based_flag ) ) / vui_time_scale
+       *
+       * <timecode's timestamp of frame part>
+       * timecode_timestamp = n_frames * fps_d / fps_n
+       *
+       * <Scaling Equation>
+       * n_frames = nFrames * ( vui_num_units_in_tick * ( 1 + unit_field_based_flag ) ) / vui_time_scale
+       *            * fps_n / fps_d
+       *
+       *                       fps_n * ( vui_num_units_in_tick * ( 1 + unit_field_based_flag ) )
+       *          = nFrames * ------------------------------------------------------------------
+       *                       fps_d * vui_time_scale
+       */
+      scale_n = h265parse->parsed_fps_n * vui->num_units_in_tick
+          * (1 + h265parse->time_code.units_field_based_flag[i]);
+      scale_d = h265parse->parsed_fps_d * vui->time_scale;
+
       n_frames =
-          gst_util_uint64_scale_int (h265parse->time_code.n_frames[i], 1,
+          gst_util_uint64_scale_int (h265parse->time_code.n_frames[i], scale_n,
-          2 - h265parse->time_code.units_field_based_flag[i]);
+          scale_d);
 
       gst_buffer_add_video_time_code_meta_full (parse_buffer,
           h265parse->parsed_fps_n,