Wrong “Frame rate: 1/1” for GXF movies (various video codecs)

GStreamer version: 1.16.2.

Operating system: Windows 8.1 x64 (desktop), macOS 10.14.6.

Reproduce:

0. Download the following movie: http://www.gvgdevelopers.com/K2DevGuide/Clips2/NTSC_SD_MPEG_LGOP_colorbar_CC.gxf (11 MiB)

1. Run the following command (substitute the real file system path):

gst-discoverer-1.0 path/to/footage/NTSC_SD_MPEG_LGOP_colorbar_CC.gxf

Expected: Frame rate: 30000/1001, framerate=(fraction)30000/1001 among other properties.

Actual: Frame rate: 1/1, framerate=(fraction)1/1 instead.

Note: FFmpeg of version git-2020-05-19-74dfc88 gives the expected values: ffprobe NTSC_SD_MPEG_LGOP_colorbar_CC.gxf outputs 29.97 fps, 29.97 tbr among other properties for the video stream.

Here's the list of affected files available from http://www.gvgdevelopers.com/concrete/products/summit/test_clips/:

AVCHD_1280x720p_5994.gxf
AVCHD_1440x1080i_25.gxf
AVCHD_1440x1080i_2997.gxf
AVCHD_1920x1080i_25.gxf
AVCHD_1920x1080i_2997.gxf
DNx145_1080i_25.gxf
DNx145_1080i_2997.gxf
DNx145_720p_50.gxf
DNx145_720p_5994.gxf
DNx220x_1080i_25.gxf
DNx220x_1080i_2997.gxf
DNx220x_720p_50.gxf
DNx220x_720p_5994.gxf
DNx220_1080i_25.gxf
DNx220_1080i_2997.gxf
DNx220_720p_50.gxf
DNx220_720p_5994.gxf
NTSC_1080i_MPEG_XDCAM-EX_colorbar.gxf
NTSC_SD_MPEG_LGOP_colorbar_CC.gxf