Extracts the iso 639-2 language information from @descriptor.
Note: Use #gst_tag_get_language_code if you want to get the the ISO 639-1 language code from the returned ISO 639-2 one.
the #GstMpegtsISO639LanguageDescriptor to fill
%TRUE if parsing succeeded, else %FALSE.
See Implementation
Extracts the iso 639-2 language information from @descriptor.
Note: Use #gst_tag_get_language_code if you want to get the the ISO 639-1 language code from the returned ISO 639-2 one.