MPEG21 Systems: File Format

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MPEG-21 SystemsFile Format DI Streaming

• Sylvain Devillers
• France Télécom RD

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Overview

• MPEG-21 in Systems
• Part 9 File format
• Part 16 Binary format
• Part 18? DI Streaming
• Addressed issue Storage and Streaming of DIs

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Storage File Format

• Issue storage and exchange of a Digital Item
• DI aggregation of several components (DID,
  metadata, resources)
• DID XML (plain text or BiMarized)
• Metadata plain text, XML (plain text, BiMarized,
  zipped)
• Resources binary
• DID is a declaration, not a physical container
• XML cannot embed binary data (except by
  base64-endoding it 33 overhead)
• Metadata documents may be large? need to
  modularize the DI in several physical entities
• No random access
• Need for a physical container ? File format
  (MPEG-21 Part 9)

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MPEG-21 File Format

• Based on ISO Base Media File Format specific
  requts
• Number of mandatory boxes
• meta box with metadata handler mp21
• DID acts as an entry point, and is
  either contained in xml box (or bxml box if
  encoded with BiM) pointed by primary item box
  (pitm)
• Other components of the DI (resources and
  metadata) may be
• included in mdat box (or be external),
• pointed by Item Location Box (iloc) and
• described by Item Information Box (iinf)
• Item name, content type, content encoding
• Dual-headed files mp21 (static) isom (timed
  metadata and resources) functionalities

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mp21
Resource 1
Metadata 1
ltDIDgt ltitemgt ltcomponentgt ltresource
ref"res1Id"/gt ltresource
ref"res2Id"/gt lt!-- so on --gt
infe
infe
infe
infe
Resource 2
Metadata 2
iinf
xml
res1Id
iloc
handler mp21
res2Id
meta
mdat
mp21 file
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DI Streaming

• New activity, CfP (April 2005), Evaluation (July
  2005)
• How to stream a DI????DI DID resources
  metadata
• DI Streaming The incremental delivery of a DI
  (DID, metadata, resources) in a piece-wise
  fashion and with temporal constraints in such a
  way a receiving Peer may incrementally consume
  the DI.
• Some new problems
• How to fragment an XML Document?
• How to assign time to the XML fragments?
• How to specify the streaming of different
  components of a DI?

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Use case1 Multi-channel DI Streaming
MPEG-2 TS
AU
AU
AU
AU
DVB-H
AU
AU
AU
AU
IP Network
AU
AU
AU
AU
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Use case 2 BSD-based adaptation

• Use case (g)BSD-based scalable multimedia
  content adaptation in distributed, streaming
  scenarios
• (g)BSD (generic) Bitstream Syntax Description,
  tool normalized in MPEG-21 DIA
• Processing
• Transformation of the (g)BSD
• Input (g)BSD style sheet
• Output transformed (g)BSD
• (g)BSDtoBin generation of the adapted bitstream
• Input bitstream transformed (g)BSD
• Output adapted bitstream new (g)BSD

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Use case 2 (ctd)

• Constraints
• (g)BSD needs to be transformed ? un-encoded
  format (no TeM nor BiM!)
• On-the-fly adaptation ? (g)BSD and bitstream
  need to be synchronized
• Live streaming ? Full (g)BSD not available
• New, adapted bitstream is generated ? AUs
  localization CTS/DTS information required for
  streaming the bitstream is no longer valid!
• Need to
• Identify Access Units DTS/CTS of the media
  resource
• Identify Process Units PTS of the (g)BSD

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Specific aspects of XML

• Unlike video audio, XML documents are authored,
  stored and exchanged in un-encoded format (text).
• MPEG standards are specified in un-encoded format
  (MPEG-21 DID, MPEG-21 DIA, MPEG-7 MDS)
• For XML, Encoding ? Compression (e.g. TeM)
• An XML document is not granular ( one piece of
  data, not a sequence)
• Content Provider ? Service Provider
• Content Provider will author un-encoded, timed
  XML document, independently from delivery
• Service Provider will encode it for a particular
  delivery mechanism
• Need for an interoperable format for specifying
  fragmentation and time so that an un-encoded XML
  document can be exchanged between Content
  Provider and Service Provider

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See DANAE demo, presented by Michael Ransburg
Thank you
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mp21
Resource 1
Metadata 1
DID
infe
infe
infe
infe
Resource 2
Metadata 2
iinf
xml
iloc
meta
mdat
meta
mp21