Ensuring High-quality
IPTV Services
Part 1
Why offer IPTV?
• Economical solution that offers new business opportunities
(revenue) for service providers.
• New rates make it possible to easily integrate voice, video and
data services over a phone line.
• Simultaneously provide multiple standard and high definition
television channels SDTV and HDTV to residences.
• Provide specialized programming such as special events,
movies, concerts only when requested by the user. (VoD)
“Ensuring High Quality IPTV Services”
IPTV Delivery– What’s the big deal?
• Why can’t I just connect a 13” TV?
• What’s so different from my old CATV?
• Why can’t I just monitor dropped packets and
% utilization?
“Ensuring High Quality IPTV Services”
TV – Traditional vs. IPTV
Traditional TV
• All channels delivered to subscribers all the time
IPTV
• Delivers a small number of channels to each subscriber
• When a subscriber changes channels, a request is sent to an
upstream server to:
- activate and deliver the new channels (Join)
- deactivate and stop delivering the old channels (Leave)
• Subscriber can’t tell that all available channels are not present.
“Ensuring High Quality IPTV Services”
IPTV Delivery – Efficient yet Fragile
Efficient
• High speed
• Low cost
• Low latency
Fragile
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Typically delivered over User Data Protocol (UDP)
depends on IP network bandwidth
depends on network components
depends on configuration
“Ensuring High Quality IPTV Services”
Customer Objections
Picture
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Black
Frozen
Tiling or Blocking
Better picture quality
Distortion or pixelization
Loss of Resolution during motion
Audio
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Dropout
Lip sync
Varying volume levels
Excessive time to change channel
“Ensuring High Quality IPTV Services”
IPTV General Delivery
• Video service providers code and compress the video signal,
• Create MPEG-2, MPEG-4 or WM9/VC-1 frames
• Video frames are typically carried by streaming IP Packets using
User Datagram Protocol (UDP) for its low latency.
• At Subscriber’s house, the video stream is decoded by a set-top
box (STB) and plays on the TV.
“Ensuring High Quality IPTV Services”
UDP – Delivering on hope
“Dropped packets are preferable to delayed packets”
A good IPTV analyzer
needs to provide
statistics for dropped
packets.
“Ensuring High Quality IPTV Services”
MPEG Compression
• Relies on the eye's inability to resolve high frequency
color changes
• Relies on the fact that there’s a lot of redundancy with
and between frames.
• Predicts the value of pixels in a frame, from the
information in adjacent frames. (motion)
• Relies on the fact that, high power tones tend to blot
out lower power adjacent tones. So if you can't hear it,
don't transmit it.
• Same principal as a *.zip file
A good IPTV analyzer needs to detect and
indicate the compression type – MPEG-2,
MPEG4, H.264 etc. Increasing compression
decreases the bandwidth but also decreases the
quality of the video.
“Ensuring High Quality IPTV Services”
Introducing I, P and B Frames
Compressing Video Frames
• Start with complete still image (I Frame)
• Partial frames (P and B Frames) set brightness, color,
motion vectors etc and are much smaller than I
Frames.
• P Frames are forward predictors and are partially
compressed.
• B Frames are both forward and backward predictors
and are heavily compressed.
• Less data is sent using this method
“Ensuring High Quality IPTV Services”
MPEG-2: Group of Pictures
Group of Pictures (GOP) – Sequence of frames
• Successive pictures within a coded video stream
• Defines how many I, P and B frames in each GOP
• M=3, N=12, GOP structure is IBBPBBPBBPBBI
• Less data is sent using GOP
A good IPTV analyzer needs to identify the GOP
type, structure and min/avg/max length. This
defines the time to recover from errors.
“Ensuring High Quality IPTV Services”
Only need to update the macro
blocks that change or move
MPEG-2 Error Recovery
• I Frames are typically once every 15 frames (1/2 second), then the next GOP
starts.
• Higher levels of compression may cause errors to last longer
• Quantization and motion estimation ensure that errors propagate quickly
A good IPTV analyzer needs to keep statistics
for I,P and B frames received vs. packets that
are lost, discarded or impaired.
“Ensuring High Quality IPTV Services”
Packet and Frame Loss
Blurred Motion
Tiling or Blocking
Single B-frame lost
Single I-frame lost
1 frame affected
14 frames affected
A good IPTV analyzer needs to detect excessive problems like
blurring and tiling and report the degradation factors contributing to
the root cause.
“Ensuring High Quality IPTV Services”
Don’t miss
Ensuring High-Quality IPTV Services - Part 2
Tel: 410-789-7890
Email: sales@fetest.com
WEB: www.fetest.com
“Ensuring High Quality IPTV Services”
Ensuring High-quality
IPTV Services
Part 2
IPTV Protocol Stack
A good IPTV analyzer needs to provide
performance statistics at all levels of the
protocol stack to isolate a problem layer.
“Ensuring High Quality IPTV Services”
Packetized Elementary Stream
• PES header contain information about the contents of the PES
packet.
• Variable length packets typically up to 64 Kbyte but may be longer
• PTS and DTS allow a decoder to reconstruct the video from I,
Band P frames sent by encoder.
• If header information is corrupted, entire PES packet will be lost.
“Ensuring High Quality IPTV Services”
MPEG-2 Transport Stream
• Fixed Length packets, multiplexes
many PES packets.
• Program Identifier (PID) contains
information to find, identify and
reconstruct program contents
• Continuity Counter (CC) – 4 bit
counter to detect loss or out of
sequence packets
• Program Clock Reference (PCR) –
clock reference to time sync the
video and audio
• Sync byte set the start of a TS
packet and allows synchronization
• Transport Error Indicator indicates
a TS packet error
A good IPTV analyzer needs to detect Sync
byte, PID and CC errors to determine the
quality of a transport stream.
“Ensuring High Quality IPTV Services”
MPEG-2
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- Program Clock Reference
PCR – Clock recovery mechanism for MPEG
42 bits – 33 bits for 90Khz and 9 bits for 27MHz.
Inserted in Transport Stream no less than every 100 msec
Excessive PCR jitter can make it impossible to decode
programs.
“Ensuring High Quality IPTV Services”
A good IPTV analyzer
must measure PCR
jitter.
PSI Tables
• PAT list all programs available in the
transport stream with their program ID
(PID).
• Each program has a PMT that lists the
elementary streams for that program.
A good IPTV analyzer
needs to detect PMT,
PAT and CAT errors.
“Ensuring High Quality IPTV Services”
Zap Time
(channel change time)
Key Factors affecting Zap Time
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Encoding
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Network
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Set top Box (leave and joins)
A good IPTV analyzer
needs to measure
channel change latency
(zap time).
“Ensuring High Quality IPTV Services”
User QoE
A good IPTV analyzer needs to provide a video preview and a
suite of QoE perceptual quality metrics including a MOS score so
that the technician knows exactly what the subscriber can expect
to see.
“Ensuring High Quality IPTV Services”
Checkpoints Affecting IPTV Quality
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Video Stream (coding, compression)
IP Core network layer (bandwidth, congestion, integrity etc.)
ATM payload (XDSL network)
ADSL2+/VDSL2 (copper loop, modem, impulse noise, rates)
Fiber (power level, modem, rates)
Set-top Box (decoding, cable/connections)
Interaction of layers (xDSL, ATM, IP and Video Transport)
A good IPTV analyzer needs to
measure IP bandwidth. Standard
definition (SD) video typically uses 3-6
Mbps but high definition (HD) can use 810 Mbps.
“Ensuring High Quality IPTV Services”
Summary: Factors Affecting IPTV
Quality Encoding and Compression
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Trade off between quality and compression level
Determines information per IP packet
Affect error recovery time
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Short term variation in packet arrival time
May affect the transport stream carrying the PCR
Direct impact on the decoding process of the customer’s STB.
Jitter
Limited Bandwidth
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Ultimately determined by customer’s access rate (xDSL or Fiber)
Packet are discarded when maximum bandwidth is exceeded
Packet Loss
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Bandwidth limitations, network congestion
Range from single, unnoticeable, missing point of video sequence to long
periods of degraded, pixilated or unavailable images.
Transmission Errors .Can’t recover packets sent with UDP
Lost I frame , there is a good chance of losing the video for a short period
Lost B/P/Si/Sp frames, impact less severe but could lead to poor image quality
Lost MPEG bytes (Sync Bite, PID, Continuity Counter, PSI Tables
“Ensuring High Quality IPTV Services”
Introducing
Turn your PC into a
Powerful IPTV Analyzer
•
Attractive price
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Automatically tests all channels with pass/fail results
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Complete Set Top Box (STB) emulation
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Full Motion Picture video preview
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Accurate audio and video MOS scores and QoE/QoS
metrics
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Comprehensive Video and Transport Stream statistics
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Drill into detail to determine root cause of problems
Generate detailed and summary pdf reports
Detects degrading conditions that simple TV viewing would
fail to detect
Correlate dropped packets with other events to determine
root cause
•
“Ensuring High Quality IPTV Services”
Call or email us to get a free demo and see the whole
picture.
Tel: 410-789-7890
Email: sales@fetest.com
WEB: www.fetest.com
“Ensuring High Quality IPTV Services”