This morning I had the pleasure of speaking to a collection of engineers from some of the leading facilities in London on the topic of MXF and some of the technical concepts behind the file format. We billed the event as being “focussed for solutions architects and engineers” and we aimed to demystify some of the fundamental concepts of MXF and file interchange, and to show how to get more from MXF as a file format and technology.
With the MXF standard now 11 years old, this complex and hugely powerful file format still continues to confuse and cause problems for even the most competent of engineers. However, MXF has a lot to offer, and if leveraged in the right way can become a reliable, feature-rich, backbone for a wide range of workflows. At ROOT6 Technology we have worked with these technologies for a long time, and have implemented them in a wide range of scenarios.
In the session we looked at some of the core concepts of MXF in detail – topics such as partitioning files for logical separation of key file components, understanding the complex ContentStorage data and class model, and defining what we mean by saying the partition and its metadata has a status of being closed or open, and complete or incomplete. These topics are obviously extensive and beyond the scope of this blog post, but they are key to understanding the philosophy and design of MXF.
Many attendees came with the aim of gaining more insight into feedback from automated QC devices, and deciphering statements such as “The Partition is not marked as Closed and Complete” and “The Partition does not have the correct KAG size”. Understanding statements such as these, the mechanisms behind them, and why they are important when creating MXF files, are very important when trying to troubleshoot interoperability issues and unruly MXF files.
MXF is implemented in a wide range of real world scenarios, and we crystallised some of the theoretical concepts we had discussed by looking at some implementations currently in use and the technical detail behind them. These included the file structure utilised by AS-11 UK DPP files, and how the Avid data model and OP-Atom files relate. Extensive workflows for these formats, and many others, are available in ContentAgent, ROOT6 Technology’s file-based workflow automation and transcoding tool.
The AS-11 UK DPP file format has a number of well thought-out optimisations that allow it to work efficiently as a long form contribution format. In particular, we studied the use of KLV fill (an empty space into which we can write new data) at the end of the Header Partition, and how this can be used to update and add metadata to the file after the initial creation. This avoids a lengthy file rewrap (recreating the whole file, a technique employed by many products), and allows the file to be instantly updated with new or altered metadata at a later date. The facility is available in ContentAgent’s AMWA certified DPP workflows.
The Avid and OP-Atom data model is complex and often not very clear, but is vital to understand for successful multi-resolution workflows and conforms, whether within an Interplay environment or not. We studied the heavy use of PhysicalSourceMOBs (a theoretical media object which describes the origin of our media, for example the source file from which the clip was transcoded), MasterMOBs (the object which defines our clip object and links our separate OPAtom files together), and the matching data models in AAF and MXF that allow the mixing of these two formats for powerful post production workflows.
Full multi-resolution, automated, Avid Ingest and Delivery workflows are available within ContentAgent, allowing for the creation of a wide range of Avid media formats. ContentAgent also leverages several advanced concepts in AAF and MXF, allowing for the automatic creation of sequences from media, creation and update of Avid database files, and the addition of complete custom metadata to your Avid media (allowing bespoke bin columns, locators and more).
To find out more, or to discuss bespoke training programs for your organisation on a wide range of technical topics, get in touch here.