Transcript Video coding standards (Cntd.)

Video coding standards (Cntd.)
• MPEG-2 (hardware technology) has been the industry-standard digital
video broadcast codec for many years for high bit rate applications. MPEG-2
requires 2 Mbps of bandwidth, which is available over coaxial lines and satellite
lines, to deliver broadcast-quality, jitter-free, digital video.
• MPEG-4 Simple Profile (SP) and Advanced Simple Profile
(ASP) were developed for streaming video over Internet connections. MPEG-4
offers a software method to compress and decompress video over a network
that provides only a best-possible connection with a wide range of data rates.
The result is not what viewers have come to expect from their televisions,
but enough to offer interesting services and enhance the richness of the
Internet experience.
Video coding standards (Cntd.)
• H.264/MPEG-4 AVC addresses the needs for greater compression,
leading to lower data rates, while maintaining broadcast quality for
video-on-demand (VOD) and high-definition television (HDTV) needs.
H.264 meets the needs of both broadcast and the Internet by cutting the
MPEG-2 bit rates in about half for digital video transmission-without a loss in
video quality.
This advance has followed the evolution of video compression science toward
higher quality and lower bandwidth, and it opens new possibilities for service
providers operating over the local copper loop infrastructure.
Using H.264/MPEG-4 AVC and new H.264-enabling technology platforms
for encoding, transport, and decoding, Telcos and ISPs can boost their
average revenue per user (ARPU) with exciting and compelling new
video-on-demand, HDTV distribution, and interactive TV services. The age of
IPTV over DSL has arrived.
Codecs
100000
Kbit/ sec
Alca tel Propr. Codec
M- JPEG
MPEG2
10000
Audio CD
MPEG4
1000
100
MP3
G.711
MP3Pro,
AAC
G.726
G.728
10
G.729
G.723.1
1
1970
1975
1980
voice
1985
1990
HiFi audio
1995
2000
2005
2010
TV qual video
Source: Alcatel
Video compression of 1024x768 pixel, 24-bit color image
H.264/AVC benefits bandwidth demand, storage
requirement, and download times
5.4. IPTV main building blocks
Streaming Server
Streaming server resides at the head- end. It can encode and
stream live streams in real-time and pre-encoded streams that are
stored on the video server. Streaming server transmits the
streams to the switch or router which transfers them over the
backbone to the central/remote offices, and from there to the end
user location.
IPTV main building blocks (Cntd.)
Video Server
Video servers fulfill several purposes. For store and forward
transmissions, video servers store digitally encoded content and
stream it through level III devices via operators’ networking
infrastructure. Video servers receive newly encoded digital
content that is uploaded from the streaming server.
Video servers also enable time shifted TV applications. Viewers
at home can then watch any program at a time convenient to
them.
IPTV main building blocks (Cntd.)
Level III Device
A switch or router that supports multicast transmission. The router
or switch resides at the head-end, interfacing with the network.
Another router or switch receives data at the central office and
transmits either to DSLAMS located there, or into end-user
network.
IPTV main building blocks (Cntd.)
DSLAM
The DSLAM (Digital Subscriber Line Access Multiplexer) resides
at the central office, connecting xDSL subscribers to the backbone
and subsequently to the head-end. When distributing TV over IP,
the DSLAM should support multicast transmission. If it doesn’t,
the switch or router at the central office has to replicate each
channel for each request. This can cause congestion at the
DSLAM input level. If the DSLAM supports multicast, it receives
one stream for each channel and replicates the stream for each
end point.
IPTV main building blocks (Cntd.)
CPE (Customer Premises Equipment)
The equipment located at the end-point that receives the TV/IP
stream. Usually the term CPE refers to the DSL modem. The DSL
modem receives the stream from the DSLAM or Level III device
and transfers it directly to the PC for display on the desktop or to
the IP STB.
IPTV main building blocks (Cntd.)
Set-top Box (STB)
Gateway between TV set/PC-TV and NT (PSTN line, satellite or
cable)
Signal processing – receiving, decoding/decompressing
STB also accepts commands from the user and transmits these
commands back to the network, often through a back channel
Functions - TV signal receiver, modem, game console, Web
browser, e-mail capabilities, video-conferencing, cable telephony
Set-top Box (STB) – Cntd.
• Components - Electronic Program Guide (EPG), CD
ROM, DVD player etc.
• Many STBs are able to communicate in real time with
devices such as camcorders, DVDs, CD players and
music keyboards
• Hardware
Data network interface
Decoder
Buffer
Synchronization hardware
Set-top Box (STB) - Cntd
Types of STB
(1) Broadcast TV Set-top Boxes - (Thin Boxes)
More elementary level set-top box with no return channel (back-end). Some
memory, interface ports and some processing power.
(2) Enhanced TV Set-top Boxes - (Smart TV Set-top boxes, Thick Boxes)
These have a return channel, usually through a phone line. Video on Demand,
Near Video on Demand, e-commerce, Internet browsing, e-mail and chat
communications
(3) Advanced Set-top Boxes - (Advanced digital Set-top boxes,
Smart TV Set-top box, Thick Boxes)
Like a PC - processors, memory and optional large hard-drives.
(4) All-in-one Set-top Boxes - (Integrated Set-top box, Super Box)
A fully integrated set-top box. Features could include everything from highspeed Internet access to digital video recording to games and e-mail capacity.
5.5. QoS issues for different types of traffic
• Voice traffic is smooth, bandwidth-benign, drop-sensitive, and delaysensitive, and is typically UDP-based. Bandwidth per call depends on the
particular codes adopted, sampling rate, and Layer 2 media employed.
Voice quality is directly affected by all three QoS quality factors (loss, delay,
and delay variation).
• Data traffic is much more varied. It can be smooth or bursty, bandwidthbenign or bandwidth-greedy, or drop- and delay-insensitive, and involves
Transmission Control Protocol (TCP) for send/receive acknowledgment and
retransmit. Traffic patterns vary by application, and data classes must
support several different priorities or application categories.
• Video traffic is bursty, bandwidth-greedy, drop-sensitive, and delaysensitive. IP-based videoconferencing has some of the same sensitivities as
voice traffic.
QoS issues for different types of traffic (Cntd.)
Data traffic is typically handled with multiple classes, where each class can be
defined and given the appropriate support based on the priority requirement of
the application that is generating the traffic. In general, enterprises should
restrict themselves to about five main traffic classes, such as:
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Mission-critical and real-time - Transactional and interactive applications with high
business priority; in some cases, real-time traffic such as voice over IP (VoIP) can be
subdivided into a separate class
Transactional/interactive - Client-server applications, messaging applications
(typically foreground activities that directly affect employee productivity)
Bulk - Large file transfers, e-mail, network backups, database synchronization and
replication, and video content distribution (background activities that do not directly
affect employee productivity and are generally time-insensitive)
Best-effort - Default class for all unassigned traffic; typically at least 25 percent of
bandwidth is reserved for best-effort traffic
Scavenger (optional)—Peer-to-peer media sharing applications, gaming traffic, and
entertainment traffic
QoS issues for different types of traffic (Cntd.)
QoS requirements for video applications
There are two main types of video applications—interactive video
(such as videoconferencing) and streaming video (such as IP/TV
content, which may be either unicast or multicast).
Provisioning for interactive video traffic:
# Packet loss should be no more than 1 percent.
# One-way latency should be no more than 150 ms.
# Jitter should be no more than 30 ms.
# The minimum priority bandwidth guarantee is the size of the
video conferencing session plus 20 percent. (For example, a 384
kbps video conferencing session requires 460 kbps of guaranteed
priority bandwidth.)
QoS issues for different types of traffic (Cntd.)
Streaming video applications
have more tolerant QoS requirements, as they are delay
insensitive and are largely jitter insensitive (due to application
buffering).
However, streaming video may contain valuable content, such as
e-learning applications or multicast company meetings, and
therefore may require service guarantees through QoS.
Provisioning for streaming video traffic:
# Loss should be no more than 2 percent.
# Latency should be no more than 4-5 seconds (depending on
video application's buffering capabilities).
# There are no significant jitter requirements.
# Guaranteed bandwidth requirements depend on the encoding
format and rate of the video stream.
QoS issues for different types of traffic (Cntd.)
Streaming video is typically unidirectional and, therefore,
remote branch routers may not require provisioning for
streaming video traffic on the customer edge (CE) in the
direction of branch to campus.
Non-important streaming video applications (either unicast or
multicast), such as entertainment video, content may be
provisioned in the Scavenger traffic class and assigned a minimal
bandwidth percentage.
Scavenger Class
The Scavenger class is intended to provide deferential services, or “less-than
Best-Effort” services, to certain applications.
Applications assigned to this class have little or no contribution to the
organizational objectives of the enterprise and are typically entertainmentoriented.
These include:
• Peer-to-peer media-sharing applications (KaZaa, Morpheus, Groekster,
Napster, iMesh, etc.)
• Gaming applications (Doom, Quake, Unreal Tournament, etc.), and any
entertainment video applications.
Assigning a minimal bandwidth queue to Scavenger traffic forces it to be
squelched to virtually nothing during periods of congestion, but allows it to
be available if bandwidth is not being used for business purposes, such as
might occur during off-peak hours.
Varied sensitivities of different types of traffic
Appendix: Bandwidth consumption of video over IP traffic in the
face of competing web surfing traffic
(No traffic shaping is present)
Additional network latency added by congestion
With QoS From Packet Shaper
(guaranteed bandwidth of 820k for video traffic)