Media, Servers and Clients

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Media, Servers and Clients

• Introduction to streaming
• Broadcast vs. On-Demand streaming
• Streaming Servers
• Media Formats
• Overcoming Packet Loss
• References

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Introduction to Streaming

• Digital media delivery over networks
• Delivery of audio and/or video content to clients
  over the Internet or an intranet
• Clients might be computers or other devices that
  play/present content

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Introduction to Streaming

• Clients might be other computers running proxy
  services, caching services, or redistributing
  content
• Clients may be custom applications
• Media may be a live stream or preexisting
  content, such as a digital media file
• Streamed media may be resistant to poor or
  unreliable connections

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Why?

• Streaming media is low cost and convenient
• Worldwide reach
• Technically quite simple as it uses the Internet,
  a global communications standard
• Makes network broadcasting very attractive to
  large- and small-scale media publishers,
  broadcasters, corporations, and individuals
• Makes broadcasting more accessible

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Broadcasting

• Normal Internet connections appear as
  point-to-point client-to-server links
• The Internet also supports a mass broadcasting
  mode where you can listen in to a data stream
• Radio stations use this model to provide
  parallel/concurrent radio and Internet services

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On-Demand streaming

• On-demand streams look like normal 1-to-1
  client-server connections
• This puts a lot more loading on the server but
  gives users much more flexibility
• For an example, go to http//www.bbc.co.uk/radio/a
  od/comedy_promo.shtml

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Streaming Servers

• Lots of choice
• Often depends on underlying platform
• and on the media formats you want to support
• e.g. Windows Media Server 2003 with Windows Media
  Services 9,
• Nullsoft SHOUTcast,
• Open source Icecast,
• RealNetworks Helix servers

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Media Formats

• Media servers often take specific formats as
  input, for example
• Sound MP3, Ogg Vorbis, WMA
• Video MPEG4, Quicktime, WMV
• However, data is normally sent over the network
  in special damage-resistant formats
• Occasional packet loss is a problem that most
  formats can get around

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Example of media Damage
Spectral damage
Pixel loss
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References

• RealNetworks media servers http//www.realnetwork
  s.com/products/connectedserver/resources.html
• Designing Web Audio book (on-line chapter)
  http//www.oreilly.com/catalog/sound/chapter/ch05.
  html
• RealNetworks vs. Microsoft, a comparison
  http//docs.real.com/docs/helix/helixserver_compar
  ison.pdf nb published by Real!

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Summary

• We have seen some of the basic reasons for using
  media streams
• We have discussed the differences between
  broadcast and on-demand streaming
• We have mentioned a few streaming servers
• And discussed which media formats might be used
  by a server
• Also we have seen the results of packet loss