Digital television via ip multicast
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Digital Television via IP Multicast. Group 15M Lee Howes (Group Leader) James Robinson (Group Secretary) Ashley Brown Jay Cornwall Simon Fothergill Lyndon Leggate. Project Summary. Allow networked PCs in the Department of Computing to receive and display television programmes.

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Digital television via ip multicast

Digital Television via IP Multicast

Group 15MLee Howes (Group Leader)James Robinson (Group Secretary)Ashley BrownJay CornwallSimon FothergillLyndon Leggate


Project summary

Project Summary

  • Allow networked PCs in the Department of Computing to receive and display television programmes.

  • Take Television channels from a Digital Terrestrial Television (DVB-T) reception card.

DVB is a registered trademark of the DVB Project. It is used with kind permission of the DVB Project and does not indicate full compliance with the relevant standards.


Background information

Background Information

Ashley BrownLee Howes


Mpeg 2 transport streams

MPEG-2 Transport Streams

  • Consists of a number of sub-streams, each identified by a number (its PID).

  • Can contain audio, video and other data for a single programme, synchronised to one time base (a Single Programme TS or SPTS).

  • Transport Streams can be multiplexed together to form a Multi-Programme TS (or MPTS).

  • Each Transport Stream contains information about the PIDs and types of each audio, video or data stream.


Digital television dvb

Digital Television (DVB)

  • Digital Terrestrial Television in the UK follows the DVB-T standard.

  • Multiple channels are broadcast on a particular frequency, in the form of an MPEG-2 Transport Stream.

  • The entire Transport Stream is processed by the receiver and the required channel extracted.

  • Additional information is included in the Transport Stream to provide channel names, subtitles, digital teletext etc.


Ip multicast

IP Multicast

Only one copy of the data is sent to the next level down in the tree, reducing network traffic

Data is only sent where it is required


Existing solutions

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 reminders on a subscription basis. Co-operates with other programmes to allow scheduled recordings.


Our solution

Our Solution

Lee Howes


Our feature list

Our Feature List

  • Distribution of Digital Terrestrial TV channels over 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.


Structure of proposed solution

Structure of Proposed Solution

Transmission (Slave) Server

Config

HardwareInterface

Master Server

DVB Mux

Listings Source

Master Configuration

Other Sources

DVB

Listings Server

Stats Database

Main Transmission Server

Client Software

Statistics

MPEG

Demux/Display

Main UI

Listings Display

Listings Data


Transmission server

Transmission Server

Ashley Brown


Tx server architecture

HTTP, STORED FILES

TRANSMISSIONSERVER

NETWORK

TX Server – Architecture


Dvb hardware interface

DVB Hardware Interface

  • The server uses a Java wrapper around the C LinuxTV API for DVB devices.

  • The API allows the card to be tuned and MPEG2 data (in particular a full DVB Multiplexed Transport Stream) to be read from 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.

I suggest Awb01 covers a popup such as:

Hardware Interface:

Linux

LinuxTV Drivers

How they work (what the API requires)

What the TS Server needs

Card->Driver->Shared Library->Java interface


Configuration

Configuration

James Robinson


Configuration1

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


Configuration demo

Configuration - Demo


Listings server

Listings Server

Lee Howes


Listings server1

Schedule Tree

System Config.

XMLTV

docTV

XMLTV

Internal Structure

Channel Selection

XML Parser

XML Source

XML Parser

Web Server

XML Source

XML Source

Listings Server


Mpeg decoder

MPEG Decoder

Jay Cornwall


Mpeg decoder1

MPEG Decoder

  • Java Media Framework (JMF) provides audio/visual playback support.

  • MPEG 2 video decoding not supported.

  • Lack of documentation and examples.

  • A different approach to audio/visual decoding was taken.


Mpeg decoder2

MPEG Decoder

Java Client

Decoding Component

(Java AWT widget)

Audio Decoder

Video Decoder

LibMPEG2

(native library)

FFMPEG

(native library)


Mpeg decoder3

MPEG Decoder

  • 720 x 576 x 32 bit: ~30% load on an Athlon 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.


Client

Client

Lyndon Leggate


Client1

Client

  • Features

    • Watch 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


Statistics

Statistics

Simon Fothergill


Statistics1

Client

Stats Manager

Stats Collector

Stats Database

PHP SQL

HTTP CGI

PHP SQL

Statistics

  • General reasons and motivation for statistics

  • Within this project: Simply, but extensibly

  • When’s popular?

  • What’s popular?


Putting it together

Putting it Together

Lee Howes


Integration and testing

Integration and Testing

  • Tested interfaces between interacting components

  • Tested and integrated in stages as components developed (using VideoLAN Client initially to test the server)

  • Transmission test to VLC in mid November


Integration and testing 2

Integration and Testing 2

  • Multiple DVB cards

  • General tests of listings such as behaviour with bad date formats

  • Long distance unicast radio feed to home ADSL from Transmission Server


A few problems

A Few Problems…

  • Initially IP multicast appeared not to work on all switches.

  • A change of multicast address range solved this.

  • Towards the end of the project, some faulty code resulted in the server saturating its connection.

  • A faulty switch flooded the network with traffic, upsetting other services.


Evaluation

Evaluation

  • A good start for further progress

  • System is flexible in design allowing for future expansion

  • Substantial problems with Java/Native interface for video could be avoided with a purely native client


Shortcomings

Shortcomings

  • Control channel not encrypted, anyone could refresh server.

  • Java event thread overcrowding causing lack of GUI responsiveness.

  • Current reliance on XML TV – radiotimes.com changed website format shortly before the presentation.


General future improvements

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, more of an issue in Linux


Feature comparison matrix server

Feature Comparison Matrix (Server)


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