AS-03 MXF Program Delivery Specification

The AMWA has released issue of AS-03 MXF Program Delivery Specification. It was developed to meet a real need from the PBS network for a single file format to deliver ready-to-air programs to their member stations.

The many stations have mix of video server makes and models, and PBS did not want a different format for each server. Although the servers could accept MXF files, the specification was very loose, and OP1A, for example, is insufficiently constrained to be considered a file delivery specification.

AS-03 describes a vendor-neutral subset of the MXF file format to be used for delivery of finished programming from program producers and program distributors to broadcast stations. AS-03 Files are intended to be delivered in their entirety to be cached before playout.

AS-03 constrains the video essence to frame-by-frame interleaving, MPEG-2 or H.264, and the audio to be PCM pairs, AC-3 or Dolby E. AS-03 files contain defined sets of metadata for identification of content and for verification of content versus progam traffic metadata that is delivered separately.

The specification can be further constrained by a “shim”. Each shim provides a set of constraints that reduce the range of variability that may be needed in well-defined categories of applications. These categories may address particular type of programming or programming genres, or they may address requirements of particular broadcast station groups, for example defining bit rate, aspect ratio, and sound essence schemes. In the case of PBS their shim defines coding rates of 25Mb/s for MPEG-2 and 18Mb/s for H.264 among many other parameters.

The development of AS-03 acknowledges the reality that the great flexibility allowed by the MXF standards impedes interoperability between equipment from different vendors. By defining a subset of MXF, AS-03 simplifies the issues around file interchange between equipment.