1. MPEG-DASH Conformance and Reference Software
ISO/IEC 23009-2
Christian Timmerer
Alpen-Adria-Universität Klagenfurt (AAU)  bitmovin GmbH
research.timmerer.com  blog.timmerer.com  dash.itec.aau.at  bitmovin.net
christian.timmerer@itec.aau.at, christian.timmerer@bitmovin.net
105th
MPEG Meeting, Vienna, Austria
July 2013

2. Outline
• Introduction and overview
• Media presentation conformance
• DASH access client reference software: libdash
• Sample software
– Clients: sample player, GPAC
– Segmenter: MP4Box
• Summary
July 2013 2Christian Timmerer (AAU/bitmovin)

3. Introduction
• Conformance and reference software of MPEG-DASH serves three
main purposes:
– validation of the written specification;
– clarification of the written specification; and
– conformance testing for checking interoperability for the various
applications against the reference software which aims to be
compliant with ISO/IEC 23009
• ISO/IEC 23009-2: media presentation conformance, test vectors,
DASH access engine reference software, sample software
July 2013 3Christian Timmerer (AAU/bitmovin)

4. Overview
• Media presentation conformance
– MPD validator: xlink, schema validation, add’l validation rules
– Segment conformance: check ISOBMFF, M2TS against DASH
specification
– Dynamic service validator: dynamic updates of the MPD
• DASH conformance sequences
• DASH access client reference software
– libdash: access to information contained in the MPD + schedule
download of segments
• Sample software
– Sample player: utilizes libdash, GUI, manual adaptation logic
– GPAC player: integrated player or embeddable DASH engine
– MP4Box segmenter: create segments + MPD based on encoded
content
July 2013 4Christian Timmerer (AAU/bitmovin)

5. MPD Conformance
Free online MPD validation service accessible at
http://dash.itec.aau.at
July 2013 5Christian Timmerer (AAU/bitmovin)
Resolves all W3C XLINK
attributes as defined in
MPEG-DASH Part 1
Performs the XML validation (i.e., well-formed
and valid) against the MPD schema as defined
in W3C XML and W3C XML SCHEMA
Performs the Schematron validation as
defined in ISO/IEC 19747-3 according to
the rules defined in MPEG-DASH Part 2

6. libdash
• MPEG-DASH Part 1 defines XML-based MPD and segment formats
(M2TS, ISOBMFF)
– MPD reflects the DASH data model providing HTTP URLs to
downloadable segments
• Adaptation logic is deliberately excluded from the specification and
left open for industry competition
• libdash provides the following features:
– Object-oriented interface into the MPD
– Access information within MPD and schedule download of segments
– External interfaces: DASH streaming control (incl. adaptation logic),
segment parser, media player – deliberately not implemented: may
vary across use cases, deployments, and go beyond what is
normatively specified
• libdash has full standard support, well-defined interfaces, and
enables integration within a media ecosystem ➜ libdash is an
enabler!
July 2013 7Christian Timmerer (AAU/bitmovin)

7. Sample Player
• Qt-based cross-platform GUI + ffmpeg based on libdash
• Works with conformance bitstreams, DASH-IF test vectors,
and major DASH datasets
July 2013 Christian Timmerer (AAU/bitmovin) 8
Select available
MPDs
Video content
Download MPD,
start/stop
streaming
Interactive
seamless switching
of AdaptationSets
and
Representations
Segment, frame,
audio, video
buffer

8. GPAC Players for DASH
• Open Source project
http://gpac.sourceforge.net
• Integrated player or embeddable DASH engine
– Multi-platform: desktop, mobile
– Playback of a very large subset of DASH conformant
content
• M2TS and ISOBMFF segments
• "static" or "dynamic" presentations
• Live, Main, OnDemand and Simple profiles
– Support for quality changes
• Interactively or automatically (bandwidth estimation and
limitation)
July 2013 9Christian Timmerer (AAU/bitmovin)

9. GPAC MP4Box for Segmenting
• Conformant generation of
– Media files (ISOBMFF, M2TS)
– MPD (all profiles)
• Support for several MPD syntax options
– SegmentList, SegmentTemplate, SegmentTimeline
• Automatic mapping of the inputs into adaptation sets,
representations, groups, assignment of roles
– Based on the content characteristics
• Flexible generation of segments and subsegments with
possible indexing, RAP alignment, and bitstream
switching features
• Generation of "dynamic" MPD and segments and
updates from pre-recorded content
July 2013 10Christian Timmerer (AAU/bitmovin)

10. Summary
• MPEG-DASH conformance and reference software available and
accessible via MPEG SVN repository
– Includes conformance bitstreams for MPDs, segments, and
combinations thereof
– libdash + sample player: http://www.bitmovin.net/libdash/
– GPAC: http://gpac.sourceforge.net
• Additional useful resources
– DASH dataset (dash.itec.aau.at): full-length movies w/ different
segment sizes, spatial resolutions, bitrates, and genre
– Distributed DASH dataset (dash.itec.aau.at): one dataset distributed
across seven sites (Klagenfurt, Paris, Prague, Torino, Crete, Delft,
Taiwan), usage of multiple BaseURL elements
– DASH Industry Forum (dashif.org): DASH-AVC/264 interoperability
points, identifier repository, reference client (dash.js,
https://github.com/Dash-Industry-Forum/dash.js/), sample players,
clients
July 2013 11Christian Timmerer (AAU/bitmovin)