Add more XMP tag to mp4

I was trying to add xmp tags extracted from XMP Tags to mp4 file by using taginject.

If some worked, most of them didn’t so i’ve look trough code to understand.

My conclusion is than tags must be sets into
gstreamer/gst/gsttaglist.c#L107
and
gst-plugins-base/blob/master/gst-libs/gst/tag/gstxmptag.c#L951

to be accepted and recorded into mp4. And that list is quite limited at the moment.

or having more tag added by a plugin.

So, next step to get job done, in my opinon, is to modify mp4mux code to register more xmp schemas and tags at start.

so i will be able to pass some extra tags trough pipeline

Am i right ?

is there a better way ?

As much as possible i would like to send my change upstream to avoid to support my own fork.