XMP is a media-metadata standard based on XML which may be used
across a variety of media formats. Some video-processing software
writes XMP data without updating the native metadata fields.
Therefore, we should aim at reading XMP metadata and give priority
of XMP data over native fields.
Pros:
- Support for *all* common media formats.
Cons:
- XML (complex, verbose, chaotic).
- Does not even come close to fulfilling its promise of being
well defined (see below).
Implement a simple XMP-parser using libxml2. Connect the XMP-parser to
the existing Quicktime/MP4 parser.
First problem encountered: According to the spec, XMP data supposed
to be put in the 'XMP_' atom. But for example exiftools instead
writes an 'uuid' atom with a special 16-byte uid. Implement both,
more options will probably follow.
Second problem: two versions of recording the creation date were found
1) The content of a <exif:DateTimeOriginal> tag.
2) The xmp::CreateDate attribute of a <rdf:Description> tag.
Here too, more versions are expected to surface and will have
to be supported in due course (with an obvious priority problem).
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
