Download iVideo helps IPTV hit primetime TextStart With the development of

iVideo helps IPTV hit primetime
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With the development of video services, users want to watch high quality video content
through a terminal of their choice, and at a place and time of their convenience. With
more broadband networks being built, more operators are providing IPTV services to
meet the diversified video and media program requirements, as IPTV supports strong
and real interactions between users and media providers. The Huawei video bearer
network solution (iVideo) provides iVSE (including FCC and RET functions) and
iRSM to fully guarantee smooth operation of IPTV services.
IPTV trends
IP television (IPTV) services have grown fast in recent years. According to a Frost &
Sullivan report, there were about 40 million IPTV users at the end of 2009, and the
number will reach 140 million in 2012. At present, the number of IPTV users is
growing most rapidly in the United States and Western Europe, while the number of
IPTV users in the Asia-Pacific region is expected to grow rapidly in the next few years.
Operators provide IPTV services usually because of the following reasons:
Competition from other operators; competitive pressures that mobile broadband
services bring to fixed broadband services; providing video as a basic service, binding
users with multiple services, and increasing user bandwidth to obtain high ARPU; and
breaking the boundaries between the TV and the PC to increase the number of
broadband users.
With the increasing demand for video quality, users are not satisfied with
standard-definition (SD) videos. More and more high-definition (HD) videos are being
provided by Digital TV, IPTV, Web TV, and mobile TV services and being supported
by an increasing number of video sources and video terminals. In America, Verizon
IPTV offers 150 HD channels. According to surveys, more than half of the TV
terminals around the world support HD services.
In addition to HD requirements, users prefer watching programs at a time and place of
their convenience. IPTV is not restricted by program schedules; instead, IPTV allows
users to enjoy various audio and video programs at any time. Offering an interactive
and customized TV-viewing experience, IPTV is gaining popularity. A survey by
In-Stat shows that time-shifting, HDTV programs, and video on demand (VOD) are the
most popular features among IPTV users.
Video basics and challenges to HDTV bearer networks
Video basics
IPTV performs video compression of received satellite signals, converts the
compressed packets to IP packets through IP streaming, and delivers the IP packets
through IP networks, thereby fully utilizing the reach and high transmission efficiency
of IP networks.
The current mainstream video compression standards are MPEG-2 and H.264.
MPEG-2 is the dominant standard among digital TV and legacy IPTV, whereas the
newly emerging standard H.264 is currently supported by some IPTV vendors. H.264 is
more sophisticated than MPEG-2 and its compression efficiency is 1.5 to 2 times the
latter's. Thus, more vendors use H.264 video compression, especially for HD videos.
Compressed by H.264, SDTV streaming is about 2Mbps, 1080i streaming ranges from
6Mbps to 8Mbps, and 1080p streaming ranges from 12Mbps to 16Mbps.
Both MPEG-2 and H.264 use the group of pictures (GoP) structure to compress videos.
The GoP comprises I-frames, B-frames, and P-frames. An I-frame, or intra-coded
frame, is a baseline frame that contains complete image information. It is the first frame
in a GoP. Every GoP has only one I-frame, and cannot be displayed if this I-frame is
lost. The I-frame contains the most data traffic and takes up more space than other
frames.
In addition, the MPEG-TS encapsulation information of a compressed video packet is
also very important. If IPTV data is encapsulated within an MPEG-TS packet, the
program specific information (PSI), including the program association table (PAT) and
program map table (PMT) information, is used to de-multiplex video, audio, and other
data in the transport stream (TS). A set top box (STB) starts decoding only after
obtaining PSI and an I-frame.
Challenges to HDTV bearer networks
Videos bring four major challenges to the bearer networks, as they require large
bandwidth, low packet loss/corruption ratio, channel change latency of less than a
second, and quick fault locating.
Large bandwidth requirements. As VOD services (including TSTV services) grow,
more bandwidth is consumed on bearer networks. While SDTV requires 2M, HDTV,
super HD and ultra HD require 8M, 50M and 200M respectively.
Sensitive to packet loss and corruption. Due to high video compression, loss of one
packet may cause mosaic or other errors in video images, and thus downgrade the user
experience. Different video coding formats have different packet loss ratio (PLR)
requirements according to DSL-Forum TR-126. The higher the transport stream bit rate,
the smaller the required PLR. HD requires that the PLR should be smaller than 1.0E-07.
Channel change latency. Analog TV does not use compression technologies; images
are immediately displayed on the terminal when they are received. The channel change
time is usually less than a second. In the case of IPTV, the terminal device will not start
decoding until it obtains the key information such as PAT, PMT, and an I-frame. As a
result, the channel change latency is unstable, and the quality of user experience cannot
be ensured. If without any special measure, the latency could reach 5 seconds, and it
will seriously impact the user experience.
Complicated operation and maintenance. Video operation and maintenance
involves O&M of IPTV, metropolitan area network (MAN), and access network. When
an IPTV service has problems, the fault must be effectively and quickly located and
cleared to guarantee the user experience.
HDTV bearer network solution
Huawei provides an innovative video solution called iVideo, which comprises iVSE
and iRSM, to address the challenges to the video bearer network.
The integrated Value-added Service Enhancement (iVSE) solution uses built-in video
cards of network devices to implement low-cost fast channel change (FCC) and
application layer re-transmission (RET) and ensure high-quality video experience.
The in-line Real Stream Monitoring (iRSM) solution delivers low-cost and effective
video operation and maintenance. The N2510 monitors the quality of video streaming
on the last-mile network. The U2520 monitors the video streaming quality of the MAN.
The Media Quality Monitor Center (MQMC) monitors the video streaming quality at
the IPTV head-end and STBs. The MQMC cooperates with the U2520 and N2510 to
deliver a unified end-to-end video operation and maintenance solution.
Solving large bandwidth requirements
Huawei has adopted two approaches to cut down bandwidth usage. One is to deploy
multicast points as close to users as possible and leverage multicast technology. The
other is to deploy content delivery networks (CDNs) for VOD and TSTV unicast
services, where the content is delivered as close to users as possible and storage used to
save bandwidth. iVSE uses built-in video cache cards to expand CDNs to the user side,
thus resulting in savings in both cost and bandwidth, and an improved user experience.
Video cache cards can be deployed in different positions to achieve optimum balance
between card-deployment cost and bandwidth saving. Huawei provides flexible video
cache card deployment solutions that are suitable for various scenarios and applications,
with support from Huawei's series of routers and OLT.
Reducing packet loss/corruption ratio: RET
Videos are very sensitive to packet loss and corruption. For IPTV, there are various
end-to-end quality factors that may cause serious packet loss or corruption, like aging
and interference of last mile copper cables, family networking, and MAN congestion.
Huawei has the automatic retransmission request (RET) mechanism at the application
layer to help reduce the packet loss/corruption ratio and remove the video mosaic.
The mechanism reveals whether a stream loses any packet via the continuity of
sequence number (SN) value in the RTP header, as the SN value increases by one when
one more IP packet is added to the same stream. Specifically, Huawei iVSE caches
every video stream for one or two seconds on the video cache card. The STB receives,
caches, and checks the video packets. Upon detecting packet loss, the STB sends a
packet retransmission request through RTCP to the iVSE card. Upon receiving this
request, the iVSE card finds the packet according to the requested SN value, and
retransmits the packet to the STB. The STB inserts this packet into the proper position
in the cache and sends the packet to the decoder, thus fixing the video stream.
The RET mechanism supports single-card multi-level deployment. If packet loss
occurs between two video cards, a lower-level video card can serve as an RET client
and request the upper-level video card to retransmit the lost packets. If the IPTV system
supports the RET function, the video card considers the IPTV system as the RET server
and sends a retransmission request to the IPTV system. In this case, the upper-level
video card can instruct, through multicast, the STBs not to send retransmission requests.
This prevents a large number of retransmission requests from being sent to the video
card. Upon receiving the retransmitted packet, the video card can multicast this packet
to the STBs.
As required by the RET mechanism, video packets should be encapsulated within RTP,
and STBs should support retransmission. Since most legacy IPTV systems output video
streams without RTP encapsulation, the IPTV systems need to be upgraded or installed
with an independent RTP encapsulation device to meet the RET requirement.
For STBs to support RET, Huawei provides two solutions. One is to load SDK software
to the STBs simply by binding the API interfaces. Currently, all the STBs Huawei
offers for IPTV systems are integrated with this function. The other one is to cooperate
with a third-party company. For example, in the case of UAE-based operator Etisalat,
STBs from four vendors already exist on the telco's network. To introduce a new IPTV
system and deliver FCC and RET functions, Etisalat employed a third-party company
named Soft@home to integrate the IPTV system and FCC and RET functions with the
existing STBs.
Solving channel change requirements: FCC
The channel change time is greatly affected by the waiting time of PSI (including PAT
and PMT) and I-frame. Based on the standard RTCP protocol, the FCC mechanism
works by decreasing the waiting time for PSI and I-frame and thus cutting the channel
change time to within a second.
When transmitting IPTV video streams, the network device uses the built-in video card
to cache the video stream of each channel for a certain time interval. The cached
information includes two or three GoPs and PSI. When the user changes the channel,
the STB sends a unicast channel change request based on extended RTCP to the video
card. The video card then sends the cached PSI of the new channel to the STB. This
effectively reduces the PSI waiting time. Then the video card unicasts the content of the
new channel (starting with the I-frame) to the STB. The STB immediately decodes the
content. The entire channel change time is therefore less than a second.
The unicast streams are sent out at a faster speed than the normal multicast speed, to
keep pace with the subsequent multicast streams. When the video card decides that the
unicast streams are keeping pace with the normal multicast streams, it sends RTCP
signaling to instruct the STB to join the multicast group of the new channel. Meanwhile,
the video card slows down the sending speed of the unicast streams by half of the
normal speed and stops sending unicast streams. The unicast streams and the multicast
streams connect to each other, even as the user is oblivious of this process.
Huawei iVSE uses a special method to decide when to stop sending unicast streams,
and when to connect the unicast streams to the multicast streams without packet loss.
When the STB receives multicast packets, the STB sends the SN value of the first
multicast packet to the video card. Then the video card stops sending unicast packets
after sending out the packet with the SN value. This method ensures that the unicast
packets connect to the multicast packets without packet loss.
FCC consumes large network bandwidth, especially when many users change channels
simultaneously. Fast unicast also has higher requirements for last mile bandwidth. For
example, some vendors require that the last mile bandwidth must be 1.3 times the
normal bandwidth. This is a huge challenge to the access network bandwidth resources.
If the operator provides 8Mbps HD video bandwidth and 10Mbps access bandwidth,
FCC cannot be deployed.
To address the bandwidth challenge, Huawei uses OLT, the CX600, and the NE series
routers to provide video cards for FCC. Operators can deploy the video cards at suitable
positions as needed. In addition, Huawei provides an intelligent method to discard
unimportant video packets during FCC to save bandwidth without affecting user
experience. With this method, the last mile network bandwidth can be just 1.1 times the
normal bandwidth, and MAN bandwidth is cut by 30%.
Like RET, FCC requires that video streams be encapsulated within RTP, and the STBs
support the FCC process. Huawei provides SDK software for upgrading of STBs. And
the IPTV systems and STBs offered by Huawei can cooperate with iVSE to support
FCC. Huawei also promotes the FCC standard process in the IETF. A draft in this
regard has already been published. When an FCC standard is published, STB vendors
only need to comply with this standard to support FCC.
In addition, to implement FCC and RET, STBs must know the IP address of every
video card that corresponds to each channel. When iVSE cooperates with Huawei IPTV
systems, STBs obtain the IP addresses of iVSE cards through the IPTV system
configuration. When iVSE cooperates with other IPTV systems, STBs contact the
iVSE center provided by Huawei to obtain the IP addresses of video cards for
delivering FCC/RET. The iVSE center is preconfigured with channel information and
the IP addresses of the corresponding channel cards.
Solving operation and maintenance requirements: iRSM
IPTV operation and maintenance is very complicated, When a problem occurs, it is
hard to locate the fault. Moreover, a small error on the network or head-end can have
serious impact on user experience. To avoid such situation, operators must quickly
locate and clear the fault to ensure high-quality user experience.
Huawei provides iRSM to quickly detect and locate faults. The iRSM uses the built-in
software monitoring module to deliver low-cost and effective video operation and
maintenance, uses Mean Opinion Score-V (MOS-V) and Real Media Rate (RMR)
detection to quickly detect faults, and uses media delivery index (MDI)/RTP detection
to quickly locate faults. All monitoring information is delivered to the U2520 and is
displayed on the U2520 to facilitate IPTV operation and maintenance.
Fault detection
MOS-V and RMR are deployed at the egress of video stream to detect the quality of
video streams output from the IPTV head-end. MOS-V determines the quality of the
video streams and shows the output quality of the head-end, but cannot determine
whether the output rate is proper. If the output IPTV video streams are of good quality
but the burst rate exceeds the upper limit of the bearer network, the output video
streams are also determined as unqualified. The RMR detection shows the rate changes
of every video stream in real time, and helps detecting whether a rate burst occurs in the
output IPTV code streams, and whether the burst rate exceeds the threshold predefined
according to the network bandwidth and lining capacity.
Fault location
The media delivery index (MDI) is an algorithm that uses the MPEG-TS encapsulation
information to measure the transmission quality of IPTV video streams over IP
networks, and it applies to all IPTV video streams that are encapsulated within
MPEG-TS packets.
It comprises two parameters: the media loss rate (MLR) and delay factor (DF). MLR
indicates the rate at which packets of the tested video streams are discarded during
transmission and thus the ideal MLR during the transmission of IP video streams is 0.
DF indicates the delay and jitter of the tested video streams in the unit of millisecond.
When the time of video contents contained in the buffer of network devices and
decoders is equal to or greater than the DF value of tested video streams, the video
display quality does not decline.
The MDI can easily and quickly obtain the packet-loss ratio and latencies of every
video stream based on the SN value in RTP header information. The Timestamp field of
the RTP packet can be compared with the local time to show the unidirectional latency
of the arriving packet (depending on the network time synchronization).
End-to-end service quality monitoring
Huawei video bearer network solution can also closely work with Huawei IPTV system
monitoring solution. The media quality monitor center (MQMC) monitors the video
quality of the IPTV head-end and STBs, the U2520 monitors the video quality of each
network node, and the N2510 monitors the video quality of the last mile network. The
N2510, U2520, and MQMC can communicate with one another, and the MQMC shows
the end-to-end video quality.
The end-to-end service quality monitoring (SQM) solution has the following
advantages:
Real end-to-end: The network device uses a built-in SQM module to monitor the
network layer quality. The video server and STB use built-in probes to monitor the
service layer quality. Thus, the real end-to-end service quality monitoring from the
IPTV head-end to the end users is implemented.
Unified management platform: The MQMC seamlessly connects to the U2520, and
functions as a unified management platform for network layer monitoring and service
layer monitoring. This management platform delivers precise and unified monitoring
indices to facilitate user management and fault locating.
Reduced TCO: The built-in probes in the head-end and the STB provide the most
precise and real IPTV quality monitoring indices. The built-in SQM module in a
network device saves space and network interfaces, and reduces the maintenance cost.
The built-in SQM module reduces CAPEX and OPEX in aspects of deployment,
maintenance, and operation.
Huawei's iVSE + iRSM solution provides FCC, RET, and end-to-end SQM functions,
serves as a full-dimensional integrated video solution for service providers, reduces
their CAPEX and OPEX, and ensures the high-quality video experience. This solution
has been utilized in constructions of more than 100 backbone networks and 600 MANs,
and is deployed by the world's leading operators, including China Telecom, China
Mobile, China Unicom, France Telecom, Deutsche Telekom, British Telecom,
Telefonica, SingTel, and Etisalat.
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