Trying to TAG an MP4 encoded file - Not working

Hi all,

I am trying to add tag information to an encoded video file in MP4 format.

for example adding tags of album & artist fields.

I saw there is a taginject element and I tried to use it to tag the album
field:

after running the following:

gst-launch-1.0 -v videotestsrc !
video/x-raw,width=3840,height=2160,framerate=30000/1001 ! vaapipostproc !
video/x-raw,width=1920,height=1080 ! queue ! vaapih264enc ! h264parse !
taginject tags="album=album12345" ! splitmuxsink location=file%003d.mp4
max-size-time=10000000000

I ran the mp4 files created with VLC player but I didn't see anything under
the media tab in the VLC.

Am I using the taginject element right?
Can someone add an example of working tagging to an encoded video file in
MP$ container?

Thanks