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Digital Television via IP Multicast

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

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  1. Digital Television via IP Multicast Group 15MLee Howes (Group Leader)James Robinson (Group Secretary)Ashley BrownJay CornwallSimon FothergillLyndon Leggate

  2. 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.

  3. Background Information Ashley BrownLee Howes

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. Our Solution Lee Howes

  9. 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.

  10. 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

  11. Transmission Server Ashley Brown

  12. HTTP, STORED FILES TRANSMISSIONSERVER NETWORK TX Server – Architecture

  13. 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

  14. Configuration James Robinson

  15. 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

  16. Configuration - Demo

  17. Listings Server Lee Howes

  18. 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

  19. MPEG Decoder Jay Cornwall

  20. 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.

  21. MPEG Decoder Java Client Decoding Component (Java AWT widget) Audio Decoder Video Decoder LibMPEG2 (native library) FFMPEG (native library)

  22. 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.

  23. Client Lyndon Leggate

  24. 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

  25. Statistics Simon Fothergill

  26. 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?

  27. Putting it Together Lee Howes

  28. 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

  29. 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

  30. 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.

  31. 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

  32. 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.

  33. 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

  34. Feature Comparison Matrix (Server)

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