Metadata in multiple-stream container formats

When I enter a lowercase three-letter ISO code into the general LANGUAGE tag field for an MP4 file, it is stored verbatim for the file as a whole, but it is not propagated into the proper field for any audio or video stream. That means, there is no way in Mp3tag to see or set any metadata per stream.

I would expect that at least if only a single audio stream and perhaps a single video stream is present in the container, Mp3tag would (also) store the language therein.

I think multiple streams should be displayed like chapters, optionally.

I too have the same problem, I have movie MP4 files which I would like to easily update the language of the default audio stream to show the correct language.

I, personally am not concerned with multiple audio streams within the MP4 file, I would be happy if you could just support the modification of the default stream to be able to add the 3 letter lower case ISO 639-2 code and the default or primary audio stream to be updated.

If this is not possible, is there another known solution for this that can be done fairly quickly.

Thanks for any help and assistance and a big thumbs up for an excellent product..