This high-level introduction describes how metadata affects the entire lifecycle of media assets. Imaging and sound recording theory describes many subtle properties for the assets. The rabbit hole is very deep. Sufficient detail is necessary to manage visual effects post production and workflow processing effectively.

If you neglect to gather metadata at any stage, forensic reconstruction may sometimes be possible. If the data is truly lost, it is gone forever.

What Is Metadata?

Video and audio recordings are described as Essence Data. They are the embodiment of the content in a tangible form.

Anything else that is not directly part of the playback process is Metadata.

There are few metadata standards and they only describe the core assets. This is sufficient for a basic content storage system. There are no metadata standards for workflow process control or lifecycle management. There are proprietary systems that do this, but they are not open-sourced.

Timed sub-title text is a special case that carries human readable text as essence data. It can also carry control signals, chapter marks and other descriptive information which is very much in the realm of metadata.

Metadata helps to make the best use of your content assets. Ideally, it should be developed in parallel with the essence format design.

The DublinCore Metadata Initiative

For a long time, the DublinCore Metadata Initiative (DCMI) has been the most well-known and often quoted example of a metadata standard. The EBU has adopted DublinCore and enhanced it to create their own metadata standard (EBUCore). Public Service Broadcasters in America have derived PBCore from DCMI. Parts of the DCMI specification are also used in the EPUB standard for eBooks.

Start with DCMI for your own metadata designs because it encapsulates a description of the fundamentals. These are covered by high-level element types originally defined in 1995. In 2000 the standard was revised to allow extensibility and controlled vocabularies. Many more properties were added in 2008 and the metadata terms were redefined as Resource Description Framework (RDF) properties. Additional inherited RDF classes are used to define domains and range limits for the DCMI properties. RDF is a W3C standard and this helps with deployment on the Internet.

Alternatives To DCMI

Whilst DCMI is a useful standard, many additional properties may need to be recorded at each stage of a workflow. Other schemas might suggest enhancements to the foundational DCMI:

Proprietary Designs

Although it has never been published as a standard, one of the most complete schemas was inside Apple's long discontinued Final Cut Server product. This was originally based on the Proximity Artbox product. Final Cut Server described over 1200 different properties belonging to a media asset. Used selectively, they were axes on which the media library could be filtered and searched. This was a very sophisticated media librarian.

Some properties described deeply technical aspects of the footage such as shutter and aperture settings. Others pertained to the ingest of movie film including the text burned into the edge of the film substrate.

Interestingly, some of these obscure metadata properties are also present in the macOS Spotlight search engine and can be selected for use in your own searches from the Finder:

Outside-in Design Process

Study all the available resources and design your own schema. This is not a trivial exercise and requires competent database design skills as well as a robust knowledge of media internals.

Reverse the design process for your content workflow by documenting the user facing application first. The metadata and database model are then governed by the requirements of the client player.

Work backwards so that each process in your workflow defines the metadata to be collected by the preceding process steps. This reveals parts of the design that require further refinement. Discovering omissions early creates a more reliable product. It needs less maintenance and exhibits fewer problems for the end-user.

Visualize the database table design in an Entity Relationship Diagram (ERD) to work out where tables are related to one another. Make the connections which define the joins in your SQL queries.

Object Oriented Programming (OOP) is recommended and leads to a collection of Object Modelling Diagrams derived from the ERD. These should also describe the state changes your model undergoes and any transaction sequences for messaging and communications protocol design.

The Object Management Group has created the Unified Modelling Language (UML) as a standardized approach to building object models. The current version is 2.5.1 and an earlier version was adopted as ISO 19501. Although UML is declining in popularity, it still has some useful ideas to offer.

Develop your own modelling conventions based on previously published work. Document them and apply them consistently throughout the project.

Complete the metadata and database model design before writing any code to shorten the development time.

Metadata Categories

A program proceeds through the workflow and is eventually scheduled for delivery to the consumer. Metadata describes the production processes, the commercial and revenue generating aspects, scheduling and delivery.

Creating a single database table to satisfy the requirements for all of these would lead to an unwieldy design with hundreds of redundant columns. Many columns are only needed for part of the lifecycle.

Good business logic design separates each stage of production into its own table. Connect them together with RDBMS joins during a SQL query.

This is a spine and role record model. Attach any role records when you need them. Some of them might not exist until late in the creative or deployment process.

The requirements are different for each part of a media item lifecycle. Each stage is represented by a different role:

Hints, Tips, Pitfalls & Gotchas

Here are a few suggestions based on real projects:

Last minute agonies - Metadata design is sometimes left until very late in the project. Likewise, documentation is often a last-minute exercise and is sometimes not done at all. This has serious consequences for your project and compromises the maintenance later on. Conceptually, the documentation is another kind of metadata, perhaps in a less structured format.

Wasted effort - Only capture information that is genuinely required to avoid wasting effort and resources.

Potential data loss - The media business exists as separate silos of expertise. The kind of metadata collected at each stage may only apply during that part of the lifecycle but it might affect things much later. The importance of the metadata being collected is not always apparent at the point of collection. It is often not captured because the operators at that point in the lifecycle have no use for it themselves.

Collaboration - The on-location shooting team cannot know what the deployment team will need without their help and advice. Collaboration and information sharing is necessary to keep everyone informed. Publish a manifest of metadata that is needed with actions on the team that can collect it most efficiently.

Too much detail - Avoid overusing modelling diagrams down to a fine-grained level. They are helpful when looking at the bigger picture but can hinder development progress if they are overused.

Not enough detail - If the metadata includes the film grain size (possibly based on the film stock and developing techniques used), an optimal scanning resolution and dynamic range can be chosen when digitizing old movie film. Smaller grain sizes give better resolution but are less sensitive to light. Adjust the brightness, contrast and dynamic range automatically to compensate.

Keep all the documents - Interactive presentations or extras on a DVD product, rely on behind the scenes material being gathered and logged during the shoot. Retain all the unused footage, paperwork and notes.

Huge benefits for free - A natural history unit was able to create a six-part series using footage that had not been previously broadcast. This saved money by not needing to send out a film crew and was only possible because the footage was accurately logged and marked as unused.

Silly mistakes - A news package editor substituted 'nice looking' background scenery from an earlier job. They did not know that the GPS metadata would be transcribed into a footer in the client player showing the location of the shot. In the middle of a high-profile news item, the strap-line suddenly described the location as being somewhere else entirely. The news outlet's credibility was damaged because the editor was unaware of the downstream processes. Check and clean the metadata in the finished product and ensure everyone fully understands the pipeline where it will be routed.

Important Metadata Standards

This is a list of the most relevant and helpful standards. Not all of these are for media applications. They may contain fragments of useful information to help you design a metadata model.

Conclusion

Streaming services require significantly more metadata than traditional broadcast ever required. It becomes increasingly important as content is shared between organizations.

Previously, job knowledge and scribbled notes were sufficient when programs were expected to air just once and never be seen again. Traditional broadcast lacked a communications channel back to the service provider so monitoring analytical data was conducted on an estimated best-efforts basis. Modern streaming platforms can very accurately measure the viewing statistics and report back instantly.

Content is now available indefinitely and the so called 'long-tail-economy' ensures that it can continue to generate valuable revenue long after it has been aired. This can only work to your benefit if you have maintained the necessary metadata to license and re-distribute your content. Repurposing to new platforms that do not yet exist is also only possible if the supporting metadata allows it.

These Appendix articles contain additional information you may find useful: