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Transcript of Doctv Presentation
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Digital Television via IP
Multicast
By
Pradeep Patel&
Vidhi Patel
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Project Summary
Allow networked PCs in the Department ofComputing to receive and display television
programmes. Take Television channels from a Digital
Terrestrial Television (DVB-T) reception card.
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Background Information
MPEG-2 Transport Streams
Digital Television (DVB)
IP MulticastExisting Solutions
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MPEG-2 Transport Streams
Consists of a number of sub-streams, eachidentified by a number (its PID).
Can contain audio, video and other data for asingle programme, synchronised to one timebase (a Single Programme TS or SPTS).
Transport Streams can be multiplexed
together to form a Multi-Programme TS (orMPTS).
Each Transport Stream contains informationabout the PIDs and types of each audio, video
or data stream.
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Digital Television (DVB)
Digital Terrestrial Television in the UKfollows the DVB-T standard.
Multiple channels are broadcast on aparticular frequency, in the form of anMPEG-2 Transport Stream.
The entire Transport Stream is processed by
the receiver and the required channelextracted.
Additional information is included in theTransport Stream to provide channel names,
subtitles, digital teletext etc.
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IP MulticastOnly one copy of thedata is sent to the nextlevel down in the tree,reducing networktraffic
Data is only sent whereit is required
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Existing Solutions
VideoLAN
Streaming of DVB channels, MPEG files, MPEG
encoder card feeds. DigiTV
Streaming of DVB channels.
Digiguide
Provides 2 weeks listings and scheduled reminderson a subscription basis. Co-operates with otherprogrammes to allow scheduled recordings.
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Our Solution
Lee Howes
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Our Feature List
Distribution of Digital Terrestrial TV channelsover IP multicast.
Selection of channels to broadcast. Multiple TV cards.
Client Programme Guide.
Accumulation of usage statistics. Programme recording and pausing of live TV
Programme reminders.
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Client Software
ListingsDisplay
Main UIMPEGDemux/Display
Structure of Proposed
Solution
Listings Data
Config
DVB Mux
DVB OtherSources
Main Transmission Server
Transmission (Slave) Server
Master Server
ListingsSource
ListingsServer
MasterConfiguration
StatsDatabase
Statistics
HardwareInterface
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Transmission Server
Ashley Brown
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TX Server Architecture
TRANSMISSION
SERVERHTTP, STORED FILES
NETWORK
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DVB Hardware Interface
The server uses a Java wrapper around the CLinuxTV API for DVB devices.
The API allows the card to be tuned and
MPEG2 data (in particular a full DVBMultiplexed Transport Stream) to be readfrom a device.
Support for hardware acceleration of MPEG-2
TS demultiplexing has been included,although is not used at present. A similar interface could be provided under
Windows.
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Configuration
James Robinson
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Configuration What configuration?
Schedule
Permissions
etc.
Required for various modules
Publish on web server
Can use Apache authentication and SSL security
XML Files Configuration tool
Creates main configuration files
Web based
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Configuration - Demo
http://doctv.doc.ic.ac.uk/admin/http://doctv.doc.ic.ac.uk/admin/ -
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Listings Server
Lee Howes
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Listings Server
XML Source
XML Source
docTV
XML Parser
Web Server
ScheduleTree
InternalStructure
XMLTV
XML Parser
XMLTV
XML Source
SystemConfig.
ChannelSelection
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MPEG Decoder
Jay Cornwall
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MPEG Decoder
Java Media Framework (JMF) providesaudio/visual playback support.
MPEG 2 video decoding not supported. Lack of documentation and examples.
A different approach to audio/visual
decoding was taken.
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MPEG Decoder
Java Client
Decoding Component(Java AWT widget)
Video Decoder Audio Decoder
LibMPEG2
(native library)
FFMPEG
(native library)
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MPEG Decoder
720 x 576 x 32 bit: ~30% load on anAthlon XP-M 2400+.
Supports MPEG 2 video and MPEG 1 /2 audio.
Potential for further codec support.
But a loss of portability. Restrictions on native access prevent
aspect ratio correction under Linux.
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Client
Lyndon Leggate
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Client
FeaturesWatch live TV (if available & permitted)
Pause live feeds & resume from that point Record programmes (scheduled or live)
Playback pre-recorded programmes
Programme reminders & auto-tune
View full TV programme listings
Usage statistics
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Statistics
Simon Fothergill
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Statistics
General reasons and motivation for statistics
Within this project: Simply, but extensibly
Whens popular? Whats popular?
Client
HTTPCGI
PHPSQL
PHPSQL
Stats DatabaseStats Manager Stats Collector
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Putting it Together
Lee Howes
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Integration and Testing
Tested interfaces between interactingcomponents
Tested and integrated in stages ascomponents developed (usingVideoLAN Client initially to test the
server) Transmission test to VLC in mid
November
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Integration and Testing 2
Multiple DVB cards
General tests of listings such as
behaviour with bad date formats
Long distance unicast radio feed tohome ADSL from Transmission Server
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A Few Problems
Initially IP multicast appearednot to work on all switches.
A change of multicast address
range solved this. Towards the end of the project,
some faulty code resulted in theserver saturating its connection.
A faulty switch flooded thenetwork with traffic, upsettingother services.
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Evaluation
A good start for further progress
System is flexible in design allowing for
future expansion
Substantial problems with Java/Nativeinterface for video could be avoided
with a purely native client
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Shortcomings
Control channel not encrypted, anyonecould refresh server.
Java event thread overcrowding causinglack of GUI responsiveness.
Current reliance on XML TV
radiotimes.com changed website formatshortly before the presentation.
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General Future Improvements
DVB streaming under Windows
Digital Radio streaming (DAB)
Streaming from an MPEG encoder Server time-shifting of channels
More configuration options
Fast, Native client, possibly using GTK to
keep cross platform Full use of JMF to make Java client work
efficiently not a problem in Windows, moreof an issue in Linux
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Feature Comparison Matrix
(Server)VideoLAN DigiTV docTV
OS
DVB Yes No Yes Yes Not Yet2
NoUDP No No No Yes Yes YesMPEGEncoder
Yes No No Not Yet1 Not Yet2 No
StoredMPEG
PS Yes3 Yes3 Nearly4 Yes3 Yes3 Yes3TS Yes Yes Yes Yes Yes Yes
Audio No No No Yes Yes YesHTTPSources
No No No Yes Yes Yes