1. MXF & AAF
16/10/08
Matthias De Geyter

2. Outline
Introduction
! Why Do We Need Them?
What Are They?
Some Concepts
! The Source Reference Chain
! Operational Patterns
A Few Practical Examples
! Workflows & Issues
A Key to Success: Application Specifications
What the Future Brings
! HD
! Increased Functionality (& Complexity)
2 VRT-medialab: onderzoek en innovatie

3. Introduction
3 VRT-medialab: onderzoek en innovatie

4. Introduction
4 VRT-medialab: onderzoek en innovatie

5. Introduction
Why Do We Need Them?
! To realize this content-central workflow model, a file format is
needed that satisfies some requirements
– Able to carry metadata, video and audio
– Possible to work on the file before transfer is complete
– Random access to material (partial file transfers)
– Open, standardized, compression-independent
– ...
! To meet these requirements MXF (the Material Exchange
Format) was developed
– Work by the Pro-MPEG Forum and the AAF Association
(now AMWA), taken to SMPTE for standardization
– The AAF Association was working on a file format for post
production: the Advanced Authoring Format
– MXF & AAF are interoperable, share data model
– Zero Divergence Doctrine (ZDD)
5 VRT-medialab: onderzoek en innovatie

6. What Are They?
:
a wrapper format intended for the interchange of
finished and almost finished audiovisual material and
associated metada
Defines the actual, physical file format next slides
:
a wrapper of metadata and essence designed for post
production interchange
Clear distinction between Object Model and Storage
Layer
More complex
6 VRT-medialab: onderzoek en innovatie

7. What Are They?
Structure of an MXF file
! Partitions
– logically divide the file in manageable parts (e.g. for error
recovery)
– 1 header partition, 0 or more body partitions, 0 or 1 footer
partition
! Index Table
– lookup table which converts a desired time offset on the
timeline to a byte offset within the file
! Header metadata: structural and descriptive metadata
– Structural metadata includes source reference chain
7 VRT-medialab: onderzoek en innovatie

8. What Are They?
Every property, set of properties, chunk of essence in an MXF file is
wrapped in a KLV triplet
! Key is 16-byte number that uniquely identifies content of triplet
! MXF Parser can skip value bytes when key is not recognized
(SMPTE RP210) by means of length
! Unknown keys: dark
Essence container divided into content packages of approximately
equal duration
! Different essence categories
– System item (metadata)
– Picture item
– Sound item
– Data item (continuous data, no picture)
– Compound item (intrinsically interleaved; e.g. DV essence)
8 VRT-medialab: onderzoek en innovatie

9. What Are They?
9 VRT-medialab: onderzoek en innovatie

10. What Are They?
A super edit decision list (EDL)
! To describe a composition on the timeline (including effects)
! Can also include essence
! More complex than MXF (effects, multi-camera)
! Does not meet all MXF requirements (process file during
transfer)
Supported by various vendors: Avid, Sony, Adobe, ...
! AAF Edit Protocol to standardize effects + restrictions
Apple (Final Cut Pro) uses its own EDL format (XML)
! Conversion is possible (Automatic Duck)
Freely available SDK
! Store files as Structured Storage, KLV and XML
10 VRT-medialab: onderzoek en innovatie

11. What Are They?
A super edit decision list (EDL)
11 VRT-medialab: onderzoek en innovatie

12. Some Concepts
The Source Reference Chain: MXF and AAF share the
same data model. 1)For MXF
Material Package Track (defines track origin)
Output timeline Sequence (defines track duration)
SourceClip SourceClip SourceClip
•Packages are SourceClip
SourcePackageID and SourceTrackID
of the Material Package segment define
identified by a Start Position SourceClip
Duration
respectively the File Package and the
Track containing the essence.
UMID (unique Top-Level Track (defines track origin)
identifier) File Package
Sequence (defines track duration)
Stored Essence
•The UMID is used SourceClip SourceClip SourceClip
as a reference Essence Container
mechanism Essence Descriptor
e.g. MPEG
SourcePackageID and SourceTrackID of the
File Package segment define respectively
the Source Package and the Track
SourceClip
SourceClip containing the derivation of the essence.
Start Position
Duration This provides historical annotation.
Source Package Track (defines origin)
Sequence (defines duration)
History
Essence Descriptor
e.g. Tape Descriptor
12 VRT-medialab: onderzoek en innovatie

13. Some Concepts
The Source Reference Chain: MXF and AAF share the
same data model. 2)For AAF
•Same concepts, different names
•Material Package ! MasterMob
•Source Package SourceMob
•Timeline Track TimelineMobSlot
•Introduces CompositionMob
•Creative decisions on how to
combine/modify essence
Reference by UMID
Deeper source packages/mobs can be used
for media tracking
•Quality preservation (limit #generations)
•Rights managements ...
13 VRT-medialab: onderzoek en innovatie

14. Some Concepts
Operational Patterns
•Control the
complexity of the
source reference
chain quot; control
complexity of MXF Tape equiv. Playlist EDL
en/decoder
•Constraints on the
file
Possible to use
Multitrack
for repurposing
Specialized pattern:
OP-Atom (mono-
essence) Multilingual
DVD
14 VRT-medialab: onderzoek en innovatie

15. A Few Practical Examples
File-based camera
Rewrapping needed
MXF OP-Atom
Avid Editor
MXF OP-Atom
MXF OP-1A
QuickTime
Rewrapping needed •Rewrapping or
CentralStorage reference to MXF
•QT
•MXF4Mac plugin
Apple editor
MAM system
MXF OP-1A
Play out
15 VRT-medialab: onderzoek en innovatie
server

16. A Few Practical Examples
Rewrapping needed
File-based camera
Rewrapping needed MXF OP-Atom
Avid Editor
MXF OP-1A
MXF OP-1A
QuickTime
•Rewrapping or
•QT reference to MXF
Central Storage
•MXF4Mac plugin
MAM system Apple editor
MXF OP-1A
Play out
16 VRT-medialab: onderzoek en innovatie
server

17. A Few Practical Examples
File-based camera
MXF OP-Atom
Avid Editor
MXF OP-1A
MXF OP-1A
Browse editing on lowres QuickTime
Central Storage
MAM system Apple editor
MXF OP-1A
Play out
17 VRT-medialab: onderzoek en innovatie
server

18. A Few Practical Examples
Multi-camera production
18 VRT-medialab: onderzoek en innovatie

19. A Few Practical Examples
Next to rewrappings (specialized companies: MOG
Solutions, OpenCube), the breadth of the standard can
cause interoperability problems, even within an OP
! E.g. timecode: which timecode? (EBU Recommendartion R122)
! Which audio in MXF wrapped DV?
Keep it simple!
Enter the Application Specification!
Revision of MXF standard (SMPTE 377M)
19 VRT-medialab: onderzoek en innovatie

20. A Key to Success: Application
Specifications
Constrain the number of options associated with the use
of MXF in a facility
Document the operational practice
Restrictions dependent on the problem space /
application:
! E.g. DV25 for news, IMX50 for general purpose programs
! Play-out automation environments: correct time code
(subtitles) and aspect ratio very important
! Archival (long-term) preservation: less tolerant regarding
standard compliance
! ...
20 VRT-medialab: onderzoek en innovatie

21. A Key to Success: Application
Specifications
Example:
! Essence is 25Mbps IEC-DV
! OP is OP-1A
! Audio within Compound Elements is not used
! A System Item is present (with accurate time code in User
Time)
! Material Package contains 1 timeline track, 1 video track and 2
or 4 audio tracks
! ...
Important to prevent and solve interoperability problems
! In quality control of existing files (later)
! As specifications for vendors
21 VRT-medialab: onderzoek en innovatie

22. What the Future Brings
New challenges arise while the basic implementations
are becoming mature
! Advent of HDTV
– Impact on bandwidth & storage requirements...
– ...Impact on compression formats (video codecs)...
– ...but also on MXF
! Increasing demand for repurposing •Higher Operational Patterns
– Proliferation of devices •Metadata e.g. about Region
– Value-added content on digital television (ROI)
of Interest
! Growing importance of workflow automation
– Basic functionality is there, let’s improve efficiency
– Service oriented architecture: services & human (source
•Media Tracking
interaction reference chain)
•Metadata (e.g. Quality
Control)
22 VRT-medialab: onderzoek en innovatie

23. What the Future Brings
HD support of MXF: evolution similar to SD??
! Again: start simple & extend functionality because of...
– Introduction of new video codecs
– Multi-channel audio: work within SMPTE
– Identification and labeling of individual audio channels (for
routing)
– Mapping multi-channel audio metadata in MXF
– ...
– Time labeling
– Next to the different implementations...
– ...problem with higher frame rates (>39)
– Not all codecs support this: time code implementation
dependent on compression format
– Revision of SMPTE 12M (12M-1, 12M-2); workaround
– EBU Recommendation (R122) needs update
23 VRT-medialab: onderzoek en innovatie

24. What the Future Brings
Metadata in MXF (not HD-specific)
! Less flexible than MAM system and its database
! Useful for e.g.
– Archival purpose
– Tightly coupled essence–metadata quite stable over time
– Subtitles, region of interest (ROI) information
– MXF validation reports
! Adding or removing metadata should happen in a flexible way
– Revision of SMPTE 377M includes appropriate
mechanism (application metadata plugin)
Higher operational patterns and media tracking
! Discussed earlier
! Application Specifications needed (AMWA; http://amwa.tv)
24 VRT-medialab: onderzoek en innovatie