The request for the development of the Specification was initiated by CNN, Harmonic and Sony in order to support the use of a single MXF file format in end-to-end production workflows. These include camera acquisition, server acquisition, editing, play-out, digital distribution and archive.
In an AMWA news release Dan Shockley, Chief Video Engineer at CNN, explains the need for the Specification: “While CNN’s news production workflows operate at a very high scale and rate of throughput, the need for efficiency and interoperability is the same as virtually every news production operation. With AS-10, we maintain interoperability between systems with a single file, eliminating the need for transcoding or rewrapping, and ultimately achieving higher levels of speed and quality in our production processes. Less tightly specified MXF implementations provided by vendors to date have not delivered this level of interoperability.” Read the full release.
The Specification is based around the use of long GOP MPEG-2 video coding at 35 and 50Mb/s for HD production. This format has proved popular for fast-turnaround news production, where HD quality is needed, but the low bit rates ease the issues of backhaul and minimize storage requirements. It is also popular for all manner of documentary and current affairs programming
Ever since the MXF standards were developed by the SMPTE, vendors and broadcasters have been trying to build interoperable workflows with varying degrees of success. Unlike baseband video interfaces, MXF allows for a great deal of flexibility in setting the many parameters detailed in the 1000 pages or so of the family of standards.
Driven by requests from members, the AMWA has been easing the task of achieving interoperability by defining Application Specifications for MXF. These are highly constrained subsets of MXF developed to suit a specific application. Examples include MXF Program Versioning, AS-02, and MXF for Delivery, AS-03. The former details a form of MXF intended to bundle MXF program files as versions and inventories for multi-format delivery. The latter, AS-03 was developed for PBS to define a common program delivery format that could be used by affiliates with a number of different makes and models of playout server.
MXF for Production
MXF for Production, AS-10 builds on the SMPTE RDD 9: The MXF Interoperability Specification of Sony MPEG Long GOP Products. Through the publishing of this detailed Specification, vendors can design interoperable products to support the format. Previous specifications had ambiguities that could lead to inconsistent implementations. AS-10 adds details to facilitate the design of interoperable products supporting the codec family.
To aid the rollout of the Specification the AMWA will make available as toolset, golden master files, a file validator, and compliance tools. These will be of use to development engineers at vendors and to broadcast engineers alike.
AS-10 has added support for growing files—read during record—an essential feature for news operations. The spanning of recordings across multiple files is detailed, enabling the use of clips recorded on more than one camera card. AS-10 also adds support for Descriptive Metadata. This was previously implemented with sidecar XML files, which still remain an option for users.
AS-10 is part of a family of Specifications, MXF at Work; enabling the adoption of MXF standards across a wide range of production workflows and use cases. Each specification details a constrained subset of the MXF standards targeting a particular application. By explicitly detailing a subset of parameters to use, vendors can design products that support interoperable workflows. To aid implementers the AMWA is rolling out toolsets to validate products as well as a certification scheme to indicate compliance with an Application Specification.
The specification can be viewed on the AMWA web site.