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The questions below have been selected from those we have been asked recently.
If they do not address a subject that is important to you, please let us know.
We will answer you personally and include the answers on this page in future editions, if appropriate.
Please do not forget - no question is too trivial.
If it is important to your organization, it will also be important to others.
Metadata is defined simply as "data about the data".
However, in a "broadcast" context is usually taken to mean extra information about the audio / video content.
Although the term itself has only recently become common in the broadcast industry, metadata has been with us for years.
Sticky labels on tape cassettes and programme notes stuffed into tape boxes are all metadata.
What has changed recently is that with the introduction of file based transfer of material,
the metadata can be added electronically to the A/V content (which is also known as the "essence").
The exciting part (and, yes, it is exciting) is that lots more useful information can be added in a
way that you have specifically chosen.
When using Diffuser to manage your organization's metadata dictionary, the simple addition of a web services interface allows quick,
easy updates to track with the industry changes to the SMPTE site. MXFixer will allow you to examine the metadata in MXF files.
When combined, the two make a powerful combination to flexibly manage standards compliance.
This question is very common as the various parts of our industry have developed similar but not identical
paper and spreadsheet databases over the years. Many organizations have tried to map their pre-existing in-house
schemas onto MXF's "DMS-1" descriptive metadata scheme. All run into exactly this difficulty, which can be very
frustrating. There are three routes out of the problem:
Accept the mappings that are very close and add your own Key-Value pairs for those where you don't find
an obvious match. For instance, you might decide to map DATELINE onto a keyword "Dateline" - which works so
long as you don't try to merge in data from someone who used the same keyword for a different purpose.
Choose one of the pre-existing entries, even if it does not appear exactly right.
you could use:
Setting Date and Time (Characterized Time Period) and or Region of Setting (Characterized Place)
for DATELINE, even though these terms sound like they are more for a drama production, perhaps, than your application.
Define your own descriptive metadata scheme with all your own familiar fields, and don't try to reuse anything
In practice, defining your own descriptive metadata scheme gives the best results.
Sadly, people are often scared off doing this because it feels like failure.
They feel that it is their own fault that their own data doesn't match a standard schema.
In fact, quite the opposite is true. Your own schema is different because your operation needs it to be specially
matched to your requirements, and indeed that is one of the things that makes it valuable to you.
For a start, "tying" the metadata to the essence means that content
is more easily found and you know what you have found.
However, with only a small amount of imagination, the possible benefits can be enormous.
In particular, you can automate many processes that require "human" knowledge to work.
As a few examples:-
For example, you can ensure that the content is accurately labelled for transmission,
with the correct format or aspect ratio going to the distribution channel.
You can be confident that rights usage is documented and used correctly,
which can be a nightmare to manage currently.
Today it can be very difficult to convincingly combine "real" video material with computer generated backgrounds,
particularly keeping the two in step through complicated moves. If changes to the camera position and lens settings
are captured during the shoot and stored as metadata, this information can control the changes in the animated background.
This will both speed up the task and give a more convincing result to the viewer.
Resale of content
If someone approaches your company to buy clips of an external shot of a café in Paris in the rain, are you likely to have that material?
More importantly, could you find it? And yet the information is known at the time of shooting and could easily have been captured.
This can make the difference between an easy sale and a difficult sale - or even no sale at all.
In reality, the list of possible benefits is endless. But only a small amount of thought is needed to identify the
business goals and key processes that can be helped.
Everybody is already using metadata in an informal way, and often without knowing it.
For many organizations, the problem is that their metadata is not in a meaningful form that is tied to the material that it references.
More concretely, some organizations are already putting together systems to link
their media systems to their business systems. Other organizations have been
put off by what they see as the magnitude of the task. Metaglue's role is to enable all sizes of company to deploy metadata systems.
What has encouraged companies to start to exploit metadata is their belief that the effort and cost to
implement these systems will pay for itself many times over in the medium and long term.
And given the time to properly introduce fully metadata and get the maximum benefits,
they are choosing to start now.
Frequently these early steps are taken by starting with a small project which they then use to
learn how it impacts on their business and its processes.
The task is not as difficult as you might expect. There is no universal solution to establishing metadata
based systems but the process of deciding what to do is quite straightforward.
It should be driven by a clear understanding of your current and future business.
What are you trying to achieve? What processes do you employ? Where do you want to take your business?
What new technologies are you likely to use? Which areas of your operation are open to change and improvements in efficiency?
Getting these questions answered first make future decisions much easier.
Metaglue is very experienced in helping organizations work through these issues and can offer support and guidance wherever necessary.
In particular, we have the tools and techniques to allow a company to start simply and add to its metadata as the usage and sophistication grows.
Although a very broad metadata dictionary has already been established by SMPTE, from the outset it became clear that not every industry requirement would be covered by a "standard" set of metadata labels (schema).
The approach taken by SMPTE is to allow extra space to be purchased by an organization for their personal use.
This space can be used for public information (and possibly "published" up to the standard SMPTE area) or kept private for use by that organization alone.
Diffuser from Metaglue enables a user to work with the standard SMPTE dictionary and add company specific information as required.
Adding extra metadata fields is very straightforward with Diffuser. SMPTE already uses Diffuser to manage their dictionary.
Thus it is very straightforward to build a set of metadata labels (a schema) to match your company's business.
The user interface for Diffuser has evolved over several years, based on the experience of Metaglue staff for their own use when
offering consultancy to customers. Consequently it already has had considerable use in real applications.
However, because this is such a new subject for many people, we have introduced a free 30 day online trial of the basic system.
This facility is to give people the opportunity to use the system, discover its ease of use and to try entering
information which relates to their organization.
When purchased, the full Diffuser package allows custom designed data forms to be quickly created, ensuring that
the user interface is both friendly and relevant to your business.
There are two possible alternatives.
If your requirements are very simple, you can ensure that they all make reference back to the SMPTE site on a regular basis.
This will work if you do not need any specialized metadata for your own organization.
Alternatively, and more elegantly, you can adopt a hierarchical structure where one "master" system
is used as the main reference for your company and regional systems connect back to this.
This is the perfect solution if you use company specific metadata.
MXF is a wide ranging standard, with many options. Initially, many first generation products were only
able to understand a limited range of these options.
However, second generation products are much more capable
This combined with many large organizations adopting their own MXF requirements as part of a
tender process has dramatically improved interoperability.
Thus, many organizations (content owners and manufacturers alike) have adopted Metaglue products as part of their own QA process.
As a side benefit, for example, MXFixer would help to resolve issues with interconnection.
Also Metaglue can offer impartial analysis of MXF or AAF files for content owners or manufacturers.
A number of organizations are helping to ensure that interoperability between manufacturers exists. Leading the way is SMPTE who work to define standards that manufacturers can use. Their work is supported by representatives of both end users of products and manufacturers.
It is important to remember that MXF is a means of wrapping the parts of a programme into a defined and recognisable form - so that you know what you’ve got within the file! An MXF file can contain a number of video or audio formats (not to mention the supplementary content) which may or may not be understood by the receiving device. While this gives a great degree of flexibility in programme exchange, it is not like 1 Volt of analogue video on a coaxial cable!
For example, if the video content being wrapped has IMX compression and the receiving device needs DV, some conversion is necessary.
Ultimately it is up to the manufacturers to ensure interoperability. organizations such as the Advanced Media Workflow Association (AMWA) can contribute on “real world” projects to ensure that the broadcaster and any combination of manufacturers achieve a workable solution. The aim is to ensure that users of products can design vendor independent solutions, safe in the knowledge that interoperability is not an issue.
When there is a common piece of video material for several variants of a programme which,
for example, have different audio and subtitle requirements, it is possible using a
clearly defined subset of MXF to link the appropriate items using metadata to define
the complete piece for delivery. This avoids wasteful and inefficient duplication
of material, in this case the video. The Advanced Media Workflow Association is
documenting this style of operation as the AMWA Application Specification for
Versioning (AMWA AS-02). Further information is available at www.amwa.tv
Avid makes more use of the extension capabilities of MXF than any other manufacturer -
both to include information for compatibility with AAF and to include bin column information.
Unfortunately, few other MXF decoders are tolerant of these extensions, even though they comply
with the SMPTE standard. MXFixer flags them all as warnings, and we advise you to do a test
import into the downstream equipment to check that it can cope.
The MXF standards define many different configurations of MXF files appropriate for different purposes.
Each one is called an Operational Pattern or OP. The most commonly used OPs are OP-1A and OP-Atom.
OP-Atom files are very similar in configuration to the media files of non-linear editing systems.
Each one is a single clip of a single essence type. OP-1A files are very similar in configuration to videotape with
Video, Sound, and Timecode interleaved frame by frame.
There is a full table of standard OPs, arranged in 3 columns and 3 rows,
covering configurations which include playlists and edit lists of single or multiple versions of programs.
Every MXF file contains a label that states which Operational Pattern is contained in the file.
Applications can use this as a simple test as to whether they can use a given MXF file. However, an OP Label by itself does not carry enough information for an application to know if it can really work with the file.
When developing a system that uses MXF files, a designer must specify many different parameters, such as:
This list of all the parameters is called an Application Spec or AS. An Application Spec usually starts life as a paper document,
and is used to help decide what equipment to buy and how to interconnect a system.
As the system gets ready to go live, the Application Spec can be used for acceptance testing,
and turned into a set of regular QA checks for incoming material and for outgoing finished programs
- what Operational Patterns will be used?
- what Essence Types (for example, MPEG or DV, PCM or compressed audio) and how many tracks will be used in each file?
- what Essence Containers (for example, MPEG Transport Streams or ISO Base Media File Format) will be used?
- what kinds of Timecode will be used?
- what Descriptive Metadata Schemes will be used?
- how will the MXF files be linked together and cataloged by asset managers?
Application Specifications can be written by standards organizations, by large media enterprise companies or by systems integrators.
For example, a standard Application Spec for Digital Cinema Packaging has been created by SMPTE DC28.
Several broadcast networks have created Application Specs for sharing programs with their affiliates.
Individual production companies use Application Specs to help them manage quality in their workflow.
"Golden File" is a type of test material, such as an MXF file, that has been engineered to be fully compliant with the standards,
and reviewed by several experts. Golden files are used to test prototypes and products for standards-compliance.
A good Golden File contains data that stretches decoders to the limits of the signals which the standard requires them to accept.
Golden files are not specific to a single vendor or product - that would be a contradiction in terms
Metaglue is a strong supporter of Open Source and, in addition to the AAF SDK,
we have been contributing to the development of the mxflib SDK for many years.
We use both of these SDKs ourselves when designing custom functions for our clients
and in our products. We know that learning how to use a full-fledged SDK can be a
daunting prospect for busy engineers, so in our MXFactory SDK we make available
a very simple API. MXFixer also provides a scripting language for writing custom MXF tests.
Last but not least, our simple Diffuser API is available for web services query and
management of metadata registries.
It is quite straightforward to achieve this. Once the unique set of metadata fields have been
decided, a schema specific to that sport can easily be created. Already, a custom schema has
been developed for the detailed documentation of one US sports organization. Metaglue made a
significant contribution to this work. Please ask for further details.
This question has really two main parts. Firstly does the file have information in all the metadata fields that I require?
Secondly, can we confirm the integrity of that information?
The Metaglue products that make it easy to answer both these questions are MXFixer and AAFixer.
These products take apart the incoming file and analyse the metadata contained in it.
There are several ways to display the information, depending on the requirements of the process at that stage.
However, a few of the options are:
When used with Diffuser this makes a powerful combination that can understand nearly all (Is this too downbeat?)
the metadata in a file and also create custom forms or XML scripts to import your own metadata.
- to show all the metadata,
- to show selected fields which are especially important to your operation or,
- to give a simple "traffic light" display to show how closely the information matches your needs.
The Digital Cinema initiative has created a powerful encryption system that works within the MXF standard.
This enables systems downstream to recognize and treat the file as an MXF file while still protecting the content.
Metaglue has experience working with this technology and can offer advice as required.
It is very straightforward to add this sort of information to any type of essence in an MXF or AAF file.
The ability to add new labels (or keys as they are known) to create a custom dictionary exists as standard
within Diffuser. It is worth making a quick check of existing keys in the standard SMPTE dictionary using the
search facility, to be sure that no-one has previously done similar work. This is particularly important
if you have the web services option in Diffuser (which enables routine updates of your dictionary
from the SMPTE standard) as metadata usage is a quickly expanding subject. It is always good to both
save your time and avoid re-inventing the wheel.
If you don't find the answer to your question or have suggestions, please let us know!