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  1. 1. MXF & AAF 16/10/08 Matthias De Geyter
  2. 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. 3. Introduction 3 VRT-medialab: onderzoek en innovatie
  4. 4. Introduction 4 VRT-medialab: onderzoek en innovatie
  5. 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. 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. 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. 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. 9. What Are They? 9 VRT-medialab: onderzoek en innovatie
  10. 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. 11. What Are They? A super edit decision list (EDL) 11 VRT-medialab: onderzoek en innovatie
  12. 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. 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. 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. 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. 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. 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. 18. A Few Practical Examples Multi-camera production 18 VRT-medialab: onderzoek en innovatie
  19. 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. 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. 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. 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. 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. 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; 24 VRT-medialab: onderzoek en innovatie