IPTV Technology

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IPTV Technology

• Team 3 Christopher Monclova, Rafael Leefoon,
  Nick Adasi, Robb Zucker Oscar Ucedo

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IPTV Transmission

• IPTV supports two kinds of services
• 1. Multicast IPTV, which consists of an emitter
  which sends the same content to multiple
• receivers the same time.
• Unicast IPTV, which also consists of an emitter
  which sends TV content to multiple receivers.
• In contrast to multicast IPTV every receiver
  receives different content. This kind of service
  can be used to send personalized TV content, e.g.
  video on demand.

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Mpeg Transport Stream
Codecs are used to encode video and audio
information into a compressed data stream.
Several Codecs combine to create a transport
stream for the media being transmitted.
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Real-time transport Streaming Protocol

• The Real-time Transport Streaming Protocol (RTSP)
  enables a client to control a media server by
• issuing commands. Necessary for Unicast .
• RTSP reuses many design principle from HTTP
• URL identifies resources
• requests contain a method name and various
  parameters
• replies contain a status code and parameters
• messages are text based.
• RTSP is a stateful protocol. The server
  maintains state of the client.
• With RTSP, every message contains a session
  identifier, enabling the server to link received
  commands to a given multimedia session.
• .

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Typical Video setup message
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Multicast

• Multicast IPTV enables a TV content provider to
  send TV content to many subscribers at the same
• time.
• IP multicast saves considerable bandwidth, since
  only one stream is transmitted over the network
• When a server multicasts data to several clients,
  it sends this data to the corresponding
• router only once.
• Similarly to regular TV, multicast IPTV supports
  multiple channels and sends them at the same
  time.
• IPTV does not broadcast to a user all channels at
  the same time.
• IPTV divides channels into groups and sends to
  each user the group that contains the requested
  channel.
• The user can switch between channels at any time.

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Multicast Service
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Unicast

• Unicast IPTV sends a given TV content to a given
  user. Video on Demand is a typical service of
• IPTV, which enables a user to request a specific
  movie and to receive it on his TV set.
• Contrary to multicast IPTV, unicast IPTV does not
  save bandwidth, since the server must send the
  content once for each user.
• Unicasting can be extremely demanding on the
  server if multiple streams must be generated by
  the media server and transmitted over the
  network.

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Unicast Service
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QoE Quality of Experience

• QoE is reliant upon error free delivery of packet
  data without retransmission.
• Very similar to packet voice where packets are
  not acknowledged
• Customers are much less accepting of poor video
  quality

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Error Free Transmission

• Pixelation due to poor transmission

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Components of a typical IPTV System

• A National head-end - Origination point of
  network Broadcasts for transmission over the IP
  network.
• Core networks - Usually an IP/MPLS network
  transporting traffic to the access network
• Access networks - Distributes the IPTV streams
  to the DSLAMs
• Regional head-end Origination point for local
  content
• Customer premises - Where the IPTV stream is
  terminated and viewed using a Set Top Box or
  Computer.

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Typical IPTV Network Design
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Datastream Delivery

• Broadcast information coming from the national
  head-end is typically distributed using MPEG-2
  encoding to the video service nodes.
• Competing compression algorithms are growing in
  popularity such as H.264 (MPEG-4 Part 10) or the
  Society of Motion Picture and Television
  Engineers (SMPTE) 421M (also known as VC-1)
• The channel content can be of standard or high
  definition.
• Distribution over the access network is done
  though digital subscriber line access
  multiplexers (DSLAM) and fiber-to-the-home (FTTH)
  services.
• The subscribers set top box (STB) acts as the
  terminating interface for the network providing
  output to the television.
• For IPTV, each channel is distributed using a
  multicast IP address.

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Factors Affecting Service

• Encoding and Compression The quality of a
  transmission can be affected from the source
  depending on the encoding technique and level of
  compression. Generally speaking increased
  compression leads to a poorer video quality but a
  smaller data stream. There is a tradeoff between
  bandwidth and compression level.
• Jitter in IPTV transmission is defined as a
  short-term variation in the packet arrival time.
  Jitter is typically caused by network or server
  congestion. To help combat jitter, STBs use
  buffers to smooth out the arrival times of the
  data packets. I the buffer overflows or
  underflows, at the STB, there is often a
  degradation of the video output.
• Limited Bandwidth Bandwidth availability is
  often an issue that affects the access network or
  the customers home network. When traffic
  utilizes the entire bandwidth, packets are
  dropped, leading to video quality degradation.
• Packet Loss Loss of IP packets may occur for
  multiple reasons
• bandwidth limitations
• network congestion
• failed links
• transmission errors
• Packet loss usually presents a bursty behavior,
  commonly related to periods of network
  congestion.

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Mpeg-2 Compression

• Frame Types
• I frames- least compressed reconstructed
  independently
• P frames use data from previous frames leading to
  greater compression
• B frames use data from previous as well as
  following video frames leading to even greater
  compression.
• Affect of errd packets is greatest on I frames.

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Key QoE Metrics

• IPTV is evolving and is not well defined for
  testing.
• The most popular parameters for testing delivery
  of IPTV packets are the media delivery index
  (MDI) and PCR jitter for MPEG-2 TS.
• Other parameters are also used in the IPTV
  network, but require intense packet inspection to
  determine transmission problems.

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Media Deliver Index (MDI)

• MDI is a standards based video quality metric
  (RFC-4445)
• MDI measures two factors
• Delay Factor
• Media Loss Rate
• Factors lead to a QoS measure that directly
  relates to the customers QoE

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Benefits of Using MDI

• MDI does not perform any type of stream decoding
  to achieve its metrics and therefore does not
  require significant real-time processing power.
• MDI can be used with encrypted media payloads.
• MDI is not dependent on any one type of
  video-encoding technique, so it can easily be
  scaled to monitor video quality on hundreds of
  simultaneous channels.
• MDI is typically sampled at multiple points
  throughout the stream path with the measurements
  serving as indicators of problems in the network
  that can be proactively addressed before they
  become service-affecting issues.
• Since MDI relies on transport-layer metrics (DF
  and MLR), it can be used to set network margins
  and it directly correlates to impending network
  problems with respect to video quality.
• Since MDI uses packet-level metrics, it helps
  validate the performance of network equipment
  such as switches and routers that play a key role
  in determining whether a packet is delayed or
  dropped.

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MDI Values increase through network.
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References

• IPTV related standardization activities from
  international Telecommunication Union Website
  http//www.docstoc.com/docs/10154710/IPTV-Presenta
  tions-Presentation5B6415D
• EXFO Test Equipment Manufacturer Website -
  http//www.exfo.com/en/applications/IPTV-Overview.
  aspx
• Video Compression picture types form Wikipedia
  http//en.wikipedia.org/wiki/Video_compression_pic
  ture_types
• Definition and Specifications of IPTV and VoIP
• Services from Adamantium Web Site
• http//www.ict-adamantium.eu/documents/deliverabl
  es/ADAMANTIUM_D2.3.pdf