Streaming

1
Streaming

• Mikolaj Leszczuk, PhD

2
Table of Contents

• Definitions
• Jitter
• QoS (Quality of Service)
• RTP (Real-time Transport Protocol)
• General overview
• Header format
• Header fields
• RTSP (Real-Time Streaming Protocol)
• Video streaming servers
• References and sources

3
Jitter

• Abrupt and unneeded change of one or many of
  signal characteristics, like
• Successive pulse interval
• Successive cycles amplitude
• Successive cycles frequency or phase
• In other words signal fluctuation metric

4
Quality of Service

• 2 different terms for QoS
• In circuit networks (e.g. telephone
  networks)Probability for connecting one
  subscriber with another subscriber
• In packet networks (e.g. Internet)Probability
  for fulfilling assumed network parameters

• QoS often referred as probability for
  transmitting a packet between two network nodes
• Reasons for problems
• Packet losses
• Delays
• Packet re-ordering
• Errors
• Jitter

5
RTP General Protocol Overview

• Supported transmission
• Unicast
• Multicast
• RTP transport controlled by RTCP protocol
• RTCP allowing for monitoring volumes of data
  transports
• WAN networks support

6
RTP Requirements for Real-Time Services

• Payload data identification
• Sequential numbering
• Time-stamp marking
• Data delivery monitoring

7
Introduction to RTP

• RTP packets usually embedded into UDP packets
• Possibility for using UDP features
• NOTE RTP is not another network layer!
• UDPRTP together good transport protocol
• Other 3rd or 4th layer protocol also applicable
  as RTP envelopes

8
Introduction to RTP Limited Real-Time

• Does not reserve resources
• Does not guarantee QoS for real-time services,
  including
• Packet delivery (at all)
• Scheduled packet delivery (even in lower layers
  do guarantee)
• Ordered packet delivery

9
Introduction to RTP Sequential Number

• Sending packet order possible to reconstruct at
  receiver
• Possible to correctly localise packet in stream
  (e.g. without decompressing video frames)

10
Introduction to RTP Applications

• RTP initially for multi-party videoconferencing
• Nowadays supporting several networked real-time
  applications like
• Video applications
• Audio applications
• Data access applications
• Applications for distributed, interactive
  simulations
• Gaming
• Monitoring applications

11
RTP and RTCP

• Real-time data transport itself carried by
  Real-time Transport Protocol (RTP)
• Additional functionality provided by RTP Control
  Protocol (RTCP)
• QoS monitoring
• Transmission of information about participants
  of current connection sessions
• Not-strict RTCP connection sessions
• Not necessary to define session participants
  (differently as in TCP)

12
RTP Sources

• Synchronization source (SSRC)
• RTP packets source
• Identified by 32-bit numerical SSRC identifier
• Sent in RTP header
• Not connected with network address (IP)
• Contributing source (CSRC)
• RTP packets source
• Delivering them to synchronized source,
  produced by RTP mixer

13
RTP Mixer Middleware System

• Reception of RTP packets from one of more sources
• Packet processing
• Possible data format alternation
• Possible connection of packets
• Further re-send as new RTP packet

14
RTP Header Format

• 0 1 2
  3
• 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
  4 5 6 7 8 9 0 1
• -------------------------
  -------
• V2PX CC M PT sequence
  number
• -------------------------
  -------
• timestamp
  
• -------------------------
  -------
• synchronization source (SSRC)
  identifier
• 
  
• contributing source (CSRC)
  identifiers
• ....
  
• -------------------------
  -------

15
Header Fields (1/8)

• First twelve octets of each RTP packet
• CSRC IDs list only if inserted by mixer
• version (V) 2 bits
• RTP version identification
• Version defined by current specifications 2
• Value of 1 used by first RTP protocol version
• Value of 0 used in first versions of vat
  application (audio transmission)

16
Header Fields (2/8)

• padding (P) 1 bit
• If set one or more additional non-data octets
  at packet end
• Last padding octet counter of padding octets to
  be ignored
• Padding useful for
• Some coding algorithms having fixed data blocks
• Transporting several RTP packets in lower network
  layer packets/frames

17
Header Fields (3/8)

• extension (X) 1 bit if set, standard header
  extended with exactly one header extension
• CSRC count (CC) 4 bits number of CSRC IDs
  after the standard header
• marker (M) 1 bit
• Marker interpretation defined by applications
• Indented for informing about important events
  like frame boundary in stream

18
Header Fields (4/8)

• payload type (PT) 7 bits
• Interpretation by application
• Static mapping between payload type codes and
  data formats
• Basic mappings for audio and video transmissions
  described in RFC 1700 document
• Possibility for dynamic definition of other
  payload types (outside RTP standard)
• Only one data type in sending RTP packet
• No multiplexing expected

19
Header Fields (5/8)

• sequence number 16 bits
• Sequential number incremented by each RTP data
  packet
• To be used be receiver for
• Packet loss detection
• Packet order reconstruction
• Random (unpredictable) initial sequence number
  value for difficulty of data capture
• Techniques for selecting unpredictable numbers
  described in EAST94 document

20
Header Fields (6/8)

• timestamp 32 bits
• Related to transmission of first data octet of
  RTP packet
• Purposes
• Synchronization
• Jitter calculations
• Received timestamp clock requirements
• Monotonic time-growth
• Linear time-growth
• Enough resolution
• More than one step per stream event (e.g.
  frame)
• Resolution related to data format

21
Header Fields (7/8)

• SSRC 32 bits
• Synchronization source ID
• Randomly chosen ID
• Assumption two synchronization sources in same
  RTP session will not have same SSRC ID
• Special algorithms for generating random IDs
• Low possibility for choosing same ID by several
  sources
• All RTP implementations ready for detecting and
  resolving collision problem
• Probabilities calculated
• Special mechanisms prepared

22
Header Fields (8/8)

• CSRC list 0 to 15 items, 32 bits each
• CSRC list identifying contributing sources for
  data included in packet
• Number of IDs given in CC field
• If more than 15 contributing sources, only 15 to
  be identified
• CSRC IDs entered by mixers, using SSRC IDs from
  contributing sources
• Example for audio packets all mixed SSRC IDs
  listed allowing for proper speaker identification
  in receiver

23
Real Time Streaming Protocol (RTSP)

• Application layer (TCP/IP model)
• On-demand delivery of real-time audio and video
• Control over delivery of data with real-time
  properties
• Beginning for end-to-end interoperability
• Sources of data
• Live data feeds
• Stored clips

24
RTSP Jumping Off Point for Negotiating

• Transports, such as
• Multicast UDPRTP
• Unicast
• UDPRTP
• TCP
• Codecs off of servers in file format independent
  way

25
Purpose of RTSP

• Single or several time-synchronized streams of
  continuous multimedia
• Network remote control" for multimedia servers

26
Video Streaming Servers

• Helix Platform (RealNetworks)
• QuickTime Streaming (Apple)
• Windows Media Services (Microsoft)

27
Helix

• Most popular streaming system
• RTSP introduced by RealNetworks
• Software producers
• RealNetworks, Inc. Helix software family
  (proprietary)
• Open-source community Helix DNA software family
  (open-source)
• Proprietary vs. open-source equivalents with
  limitations on both sides

28
Helix Platform Streaming Options

• Multicast
• UDPRTP transport
• Unicast
• HTTP controlled
• TCP transport
• RTSP controlled
• TCP transport
• UDPRTP transport

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Main Helix Platform Components (1/2)

• Media creation
• RealProducer (Plus)
• Helix Mobile Producer
• Media servers
• Helix Server family (several versions)
• Helix Proxy

30
Main Helix Platform Components (2/2)

• Media players
• RealPlayer
• RealPlayer for mobile
• RealPlayer Enterprise
• Media player management RealPlayer Enterprise
  Manager
• Codecs third-party plus own
• RealVideo
• RealAudio

31
Helix DNA Platform
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Main Helix DNA Platform Components (1/2)

• Media creation
• Helix DNA Producer
• Media servers
• Helix DNA Server
• RTSP Proxy Kit

33
Main Helix DNA Platform Components (2/2)

• Media players
• Helix Player
• Desktop systems
• Laptops
• Helix DNA Client
• Set-top Boxes
• Mobile phones
• MP3 players
• PDAs
• Codecs most of popular ones supported

34
QuickTime Streaming Server Introduction (1/2)

• Product of Apple
• Current version 5
• Designed to work only in Mac OS X Server
  operating system
• Shipped with operating system no additional
  license fees

35
QuickTime Streaming Server Introduction (2/2)

• Support for several formats of digital media and
  codecs
• Older and native QuickTime
• Newest standards, including
• MPEG-4
• 3GPP/3GPP2
• H.264/AVC

36
QuickTime Streaming Server Basic Features (1/5)

• Possibility for receiving streams on several
  platforms
• Streaming in standards acceptable for all players
  at all platforms
• To be used as bridge for other streaming servers

37
QuickTime Streaming Server Basic Features (2/5)

• RTP/RTSP streaming
• Multicast
• Unicast
• Support for MPEG-4 format streaming
• MP3 files streaming
• Usage of Icecast standard protocols
• Every HTTP MP3 player

38
QuickTime Streaming Server Basic Features (3/5)

• Live Broadcast using QuickTime Broadcaster
  application
• Live broadcast simulation based on pre-stored
  content
• Video on Demand (VoD) streaming
• HTTP Fast Start streaming

39
QuickTime Streaming Server Basic Features (4/5)

• QuickTime Streaming Server Publisher
• Creation of play-lists
• Server content management
• Administration methods
• Local
• Remote
• Web-based
• Logs and efficiency statistics allowing for
  real-time
• Monitoring
• Planning

40
QuickTime Streaming Server Basic Features (5/5)

• Good Quality of Service implementation
• Instant-On function for reducing streaming
  transmission startup time in case of broadband
  connections
• Skip Protection function for improving multimedia
  stream quality

41
Darwin Streaming Server vs. QuickTime Streaming
Server

• Darwin Streaming Server open-source version of
  QuickTime Streaming Server
• Based on same code as QuickTime Streaming Server
• Applications
• QuickTime and MPEG-4 streaming for Mac
  alternative platforms
• Windows
• Linux
• Solaris
• For modifying/extension of existing server source
  code

42
Windows Media Services
43
Windows Media Services Introduction (1/2)

• Microsoft Media components
• Windows Media Tools creating video content
• Windows Media Services streaming server
  transmitting video content
• Windows Media Player playing video content
• Complete solution

44
Windows Media Services Introduction (2/2)
45
Windows Media Services Requirements

• Network neighborhood, for
• Administration
• Content storage
• TCP/IP networking
• Microsoft Windows operating system
• Server edition only (for streaming server)

46
Windows Media Services Windows Media Tools

• Content creation, for
• Live transmissions
• On demand transmissions
• Conversion to Windows Media format from other
  formats
• WAV
• AVI
• MPEG-1
• MP3

47
Windows Media Services Windows Media Tools

• Windows Media Encoder for video content creation
• Build-in HTTP server
• Encoding of live and pre-stored content

48
Windows Media Services Windows Media Tools

• Creation of video-based presentations
• Video plus
• Graphics
• Tags
• Script commands
• Indexes
• Applications
• Windows Media Author
• Advanced Script Indexer

49
References and Sources (1/2)

• RTP RTP A Transport Protocol for Real-Time
  Applicationshttp//www.rfc-editor.org/rfc/rfc188
  9.txt.
• REYN94 Reynolds, J., and J. Postel, "Assigned
  Numbers", STD 2, RFC 1700, USC/Information
  Sciences Institute, October 1994.
• EAST94 Eastlake, D., Crocker, S., and J.
  Schiller, "Randomness Recommendations for
  Security", RFC 1750, DEC, Cybercash, MIT,
  December 1994.
• ATM The ATM Forum http//www.atmforum.com/

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References and Sources (2/2)

• WAJDA K. Wajda, Spoleczenstwo Globalnej
  Informacji Budowa sieci komputerowych w
  technologii ATM, Fundacja Postepu
  Telekomunikacji
• PAP Z. Papir, Ruch telekomunikacyjny i
  przeciazenia sieci pakietowych, Fundacja
  Postepu Telekomunikacji
• JITT Jitter Wikipedia http//en.wikipedia.o
  rg/wiki/Jitter
• QOS Quality of Service Wikipedia
  http//en2.wikipedia.org/wiki/Quality_of_Service
• ATMWIKI Asynchronous Transfer Mode
  Wikipedia, http//en.wikipedia.org/wiki/ATM

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Koniec

• Dziekuje za uwage

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QuickTime Streaming ServerGUI-Based Server
Management
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QuickTime Streaming ServerStreaming Architecture