MP4 - trun atom data not shown properly

[jordicenzano]

Steps:
1- Gerenerate fmp4 with:

ffmpeg -f lavfi -re -i smptebars=duration=15:size=320x200:rate=30 \
-pix_fmt yuv420p -c:v libx264 -b:v 250k -g 30 -keyint_min 120 -profile:v baseline -preset veryfast \
-f mp4 -movflags empty_moov+omit_tfhd_offset+frag_keyframe+default_base_moof /tmp/test.mp4

2- Show atoms in thumbcoil and Bento MP4 dump

You will see trun: sample_count is not shown in thumbcoil