SET TOP BOX

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SET TOP BOX

• What is set-top box ?
• An interactive device which integrates the video
  and audio decoding capabilities of television
  with a multimedia application execution
  environment. It provides a user friendly
  interface offering personalized multimedia
  services and regular cable TV service.

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• How's STB different from multimedia computer ?

Multimedia computer STB
Expensive and versatile device Inexpensive limited functionality device primarily targeted at entertainment
Might be equipped with floppy or a hard disk drive Not likely to be so equipped
Can execute a wide variety of application programs Limited scope of applications that can be executed
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Digital video networks(DVN)

• Digital television advantage.
• Digital video delivery requirements
• High bandwidth.
• Fibre cable, satellite, broadcast and computer
  networks can be used.
• Traditional cable networks analogue systems and
  their drawbacks.
• Satellite and terrestrial networks.
• Internet suitability for interactive network and
  drawback.

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• DVN need to deliver a high bandwidth stream into
  consumer homes and a low bandwidth communication
  layer for interaction between the STB user and
  the service provider.
• Cable operators approach for DVN.
• Need to extend unidirectional coaxial networking
  with a communication path from subscriber home to
  cable service gateways that can control the
  content being sent to subscriber.
• Advantage of video compression technology.
• Constraints with cable networks.

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• Telephone companies approach.
• Advantage with telephone companies.
• Already have set up for P2P and technology for
  control and service gateways to manage wide area
  switched star networks.
• Drawback.
• Low bandwidth between head end equipment and
  consumers home.

6

• Video dial tone network.
• Designed with fibre optic backbone with coaxial
  cable or fibre optic cable to the home.
• Figure.
• Has two types of networks
• Unidirectional broadband network to distribute
  video and audio as MPEG-2 transport packets over
  ATM.
• Bidirectional TCP/IP low speed signalling
  network.

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Set Top Box Hardware Architecture.

• Requirements based on functionality.
• Should have MPEG-2 sub-system to decode MPEG-2
  video and audio.
• Should enable user to download custom
  applications and execute them on the STB which
  requires a general purpose microprocessor in the
  STB with an architecture that supports control of
  the different devices.
• Various hardware components.
• Figure.

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STB software architecture

• For personalized interactive services, a set top
  box should be addressable in the video dial-tone
  network, thus providing P2P communication between
  a video and information provider and a user. It
  should also have the ability to download client
  applications and execute them locally.
• The control software on the set top box ties
  together all the hardware components into a
  functioning unit.

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• STB software has two parts.
• System software which provides the DAVID
  application programming interface.
• Application software that provides cable TV
  functionality or some other personalized
  multimedia service.
• DAVID system software includes.
• Operating system(os-9) kernel.
• Device drivers.
• File manager.
• Operating system(os-9) kernel is responsible for
  the following
• Scheduling different tasks for the
  microprocessor.
• Managing inter-process communication between
  different tasks and processes in the STB.
• Memory management for the multi-tasking operating
  system.
• Maintaining the real time clock for the system.

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• Device drivers
• The various hardware components of STB have
  programmable registers that can be used to
  control the behaviour of the components. Each
  one of these devices has a device driver task
  associated with it that allows the main
  microprocessor to manage the device. The device
  drivers also perform interrupt servicing for the
  components and hide the details about device
  addresses and actual register values.
• File manager
• File manager available for each device driver and
  provides a file like interface for the device.
• file like interface provides a uniform layer
  of abstraction and is generic to all the
  capabilities of STB.
• RTNFM, SPF, MPFM, AUXMAN.

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• Application Software.
• interoperability of softwares.
• Navigator.
• Downloaded applications.
• Operating system upgrade.
• Other resident applications config, display

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Conclusion

• For the hardware there will be strong trend
  towards very flexible decoders in the form of
  signal processors and fast CPUs possibly even
  combined with even combined in one large digital
  processing CPU. The arrangements for sending
  information from terminal(STB) into the network
  can be improved both in latency and in
  throughput. The graphic subsystem is likely to
  grow towards 3D applications.
• STB software hides the machine and network
  specific features of a set top box under a layer
  of abstraction and provides a user friendly
  interface to access cable television and video
  information services. The software components are
  likely to increase with more integration and more
  programmable components. This will increase the
  flexibility of STB.