Technical metadata is usually stored in the media file, although it can sometimes be in a sidecar file in the same directory as the media file. The available file-based metadata varies depending on the file format. The usage depends on the NLE and platform. The alternative to file-based metadata is the metadata stored in a Premiere Pro CC Project, Media Composer Bin or Final Cut Pro X Library.
File based metadata always travels with the file, whereas metadata in a Project, Bin or Library is only available in compatible versions of the same NLE.
There are many variations on file-based technical metadata, including:
- AV Foundation Metadata as used by Final Cut Pro X.
- Avid AAF or MXF metadata (and in old versions of Avid products, OMF)
- Any MXF metadata (Panasonic’s P2 Media (DVCPRO HD and AVC-I) and Sony’s XDCAM EX store media and metadata in the MXF format.)
- QuickTime Metadata (since Final Cut Pro 5.1.2, and in every version of Final Cut Pro X, source metadata has been stored inside the media file.)
- QuickTime metadata is effectively obsolete.
- Adobe XMP — eXtensible Markup Protocol — metadata. Like AV Foundation and QuickTime metadata, XMP metadata is infinitely flexible. With P2 and XDCAM metadata the metadata ‘slots’ (entry fields) are fixed and only Panasonic or Sony can change them or extend them.
- REDcode Metadata carries a lot of information about the exposure and color information.
The Advantages and Disadvantages of File Based Metadata
The primary benefit that file based metadata provides is that it cannot ever get lost. Where the media travels, the metadata travels with it, so it can be recovered at any time.
The disadvantage is that each file can only contain one set of metadata per file, with the exception of Adobe’s XMP Metadata, which supports time ranges. This disadvantage becomes apparent when clips are divided into selects or subclips and different information needs to be added to each clip, even though multiple clips come from the same media file. This metadata is entered into the project and does NOT travel with the file.
AV Foundation Metadata
The native media framework for Final Cut Pro X is very new. Since it’s official introduction in OS X 10.7 Lion AVFoundation has been developing rapidly. Metadata in AVFoundation got a major boost in OS X 10.10 Yosemite.
AAF and MXF
One of the things that distinguished Avid’s Open Media Framework — OMF — from AVI and QuickTime files was that it contained metadata and carried it within the file. When Avid felt that OMF was approaching the end of its official life, they started a process within SMPTE for a more advanced format. The result was AAF — the Advanced Authoring Format.
AAF is designed to comprehensively track all metadata and usage for any specific media file. When Avid moved on from OMF they decided to create an open industry standard with contributions from many companies. AAF was supposed to track all uses of a media object, its location and all formats it might exist in.
In AAF parlance – as in our discussion of media vs metadata – a media file (be it film, data or videotape) is called “essence” to distinguish it from the metadata. In theory, an AAF file can be completely independent of the essence as long as the AAF file knows where the essence resides. All changes to, and use of, the essence is tracked in the AAF file.
AAF is the foundation of Avid’s project format, and can be imported and exported from Premiere Pro CC and Resolve. It remains somewhat harder for developers to work with than XML because AAF is a binary format and there are licensing issues.
The other reason that AAF failed to live up to its promise of being the universal format, is that some companies — Avid in particular — kept much of their AAF metadata “dark”, meaning that it cannot be “seen” and converted to another format, even when using tools like Automatic Duck’s Pro Export FCP or Pro Import FCP or Premiere Pro CC.
The Material eXchange Format is a subset of AAF from the AAF Association. It’s a subset of the AAF metadata fields that are relevant for media acquisition.
MXF carries a subset of the AAF metadata, technically known as the “Zero Divergence Directive” (While it sounds like an episode of The Big Bang Theory, all it really means is that manufacturers can’t deviate from the standard, which is a good thing.)
What is important is that it gives the industry a standard format for media and metadata together. Panasonic’s P2 Media (DVCPRO HD and AVC-I) and Sony’s XDCAM EX store media and metadata in the MXF format.
There are two types of QuickTime metadata: the traditional Annotations that have been with QuickTime since version 3 (and cover common items like Album, Artist, Director, Title, Performer, etc.); and the QuickTime metadata that we’re interested in which was introduced with Final Cut Pro 5.1.2 and used by Final Cut Pro until version 7. This metadata is used to carry the Source metadata to the media file via Log and Transfer. Final Cut Pro X reads this metadata, but will not write it outside of Log and Transfer.
AVFoundation reads both forms of QuickTime metadata and is rapidly gaining more flexible, and easier-to-use, metadata functions, which is fortunate because QuickTime (other than the MOV container) is officially obsolete, even though it remains supported for playback within macOS.
Adobe have developed the eXtensible Markup Language for metadata as an “open standard”. It is proprietary to Adobe, in so far as they are the only ones doing development on the architecture, but it is open for anyone to use, and Adobe provide useful tools and code samples for those who want to experiment.
It is also highly flexible. You can add any metadata scheme to XMP metadata. There is no restriction on what metadata is carried in the file.
There is one set of metadata for the file and it is a superset of all file-based metadata. So, while not developed by Adobe, in Adobe applications EXIF, Photoshop and Dublin Core metadata all display in the XMP metadata panel. Photoshop metadata is proprietary to Adobe.
XMP metadata will be a metadata scheme you will need to know about in the future. It can be maintained through the Adobe applications from origination through to distribution. It is not directly supported in Final Cut Pro X nor in Media Composer.