Transcript Assignment #3

Networked Life: 20 Questions and Answers
(M. Chiang, Princeton University)
Q17: IPTV and Netflix: How can the
Internet Support Video?
Prof. Hongseok Kim
© 2014 Networking for Information Communications and Energy Lab.
Video watching is changing
 Content type
»
User generated as well as licensed
 When
»
DVR on IPTV, HBO Go …
 Where
»
Anywhere with Internet connectivity
 How
»
Almost any device
2
How much




Hulu : 31 million unique viewers in Feb. 2012
Comcast : 39 million, watching 205 million videos
US : 100 million IPTV users
YouTube and Netflix : half of Internet usage
3
classification1
 Precoded
»
Vast majority is precoded
»
The content is already encoded and stored somewhere
 Real time
»
Sports, news, weather
 Two way interactive
−
Online gaming
−
Video conferencing
4
classification2
 Download
 Streaming
 Netflix and YouTube
»
Device does not keep a local copy
5
classification3
 Channelized
»
Follow the schedule of each channel accordingly
−
TV, DVR
 On demand
»
VoD(Video on Demand)
−
YouTube, Netflix, some premium TV
 NVoD
»
Near Video on Demand
»
Which staggers the same channel every few minutes, so that within a
latency tolerance of that few minutes, you get the experience of VoD
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classification4
 Multicast
 Extreme form : broadcast
»
Everyone is in the multicast group
 Unicast
7
IPTV
 Over private and managed network, often with a set-top box
on consumer premise
 IP convergence
 Cost
 Flexibility
 compression
8
IPTV
9
VoI
 Over public networks
 Client-server without fee
»
YouTube, ABC and BBC
 Client-server with fee
»
Netflix, Amazon Prime, Hulu Plus, HBO Go
 P2P
10
VoI
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Quality
 Bit rate / distortion
»
Motion
»
Screen resolution
»
Viewing distance/screen size
»
Efficiency of compression
»
SD, HD, UltraHD
 Delay
 Jitter
12
Questions
 How can the pipe take on so many bits per second?
 How to keep track of video?
 How to support quality of service over best effort network?
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Layers
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Video
 Sequence of frames moving at a particular speed
 Each frame is a picture consists of pixels
 Each pixel is {colors, luminance} encoded in bits
 Bit rate = bits per frame * number of frames per second
15
Compression
 Remove redundancies in signals
 Lossless compression
 Lempel-ziv
 Lossy compression
 Tradeoff between compression ratio and resulting fidelity
16
Rate distortion curve
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Which bitrate?
 Distortion tolerable
 Channel condition
 Usage quota
18
What to compress
 Redundancies
 Frame-to-frame similarities
 Human visual limitations
 Transform coding
 Statistical structures
 Huffman coding
19
Standards
 MPEG1: 1992
»
VCD, 1Mbps
 MPEG2(H.262): 1996
»
DVD, 10Mbps
 MP3
»
Standard for the online music industry
»
12:1 compression ratio
 MPEG4: 2000
 MPEG4 Part 10(H.264): 2004
»
HDTV, 15-20Mbps, Blu-ray, 40Mbps
 H.261, QuickTime, Windows, Media Player, Flash, Real
Media…
20
Inter-frame prediction

21
Metrics
 Bitrate efficiency
»
If GoP longer, bit rate becomes lower
 Error resilience
»
If an I frame lost
 Instant channel change
»
For channelized video content, the ability to change channels fast is
important
22
Example
23
I frame dropped

24
P frame dropped

25
B frame dropped

26
Application layer
 IGMP
 Membership-query
 Membership-report
 Leave-group(optional)
 Unicast help
 SIP
27
RTSP
28
Transport layer
 UDP
 Connectionless
 Differences compared to TCP
 No congestion control
 No retransmission
 Latency vs. reliability(tradeoff)
 RTP
29
Another use of UDP
 Network management protocols
 SNMP
 RIP
 Number of states and number of parallel sessions
 Handshake and tear down overhead
 Header overhead
»
8bytes(UDP)<20bytes(TCP)
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Latency-jitter tradeoff
31
Optimization

»
𝑷𝒊 : the time at which packet i is displayed to the user
»
𝑽𝒊 : the time at which packet i is transmitted(unit step)
»
𝑨𝒊 : the time at which packet i is received
32
Solution
33
34
35
Summary
 IP has become the basis of video content
 Content being decoupled from delivery channels and
devices
 Quality of service provided through different mechanisms
 Layering in action
36
Thank you!
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