Doctv Presentation

8/4/2019 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

Documents

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