MPEG Technology Primer
CX380 • MPEG Explorer Option
Rev. A02
Agenda
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Introduction to MPEG
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Digital Video Broadcast (DVB)
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Video Compression techniques
Compression standards
Frame Types and Structure
Program Specific Information
MPEG & DVB relationship
DVB Service Information (DVB-SI)
MPEG transport stream (TS)
Packetized Elementary Streams (PES)
MPEG clock mechanisms (PCR, PTS, DTS)
ETSI TR 101 290 test recommendation
CX380 CATV analyzer
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
Network Overview
MPEG Explorer option and video/audio metrics
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Introduction to MPEG
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Video Medium Evolution
Film
• Invented in late 18th century, still widely used today
VHS
• Released in 1976, rapidly disappearing
DVD
• Released in 1996, dominant for over a decade
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The Analog to Digital Transition
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The “N word”
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Economics
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Analog signals are prone to corruption by Noise
Optical media is cheaper to produce than magnetic media
Video digitization
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New digital video cameras capture directly to digital format
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Old film can be scanned with special machines to produce a digital stream
Video Encoding/Compression
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Once video is in a digital format, it makes a lot of sense to compress it
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Similar to image compression, we need to store video data as efficiently as possible

maximize quality and minimize storage space and processing resources
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we can exploit correlation in both space and time domains
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Digital Video Technologies Today
Resolution
Uncompressed
HDTV
MPEG2
H.264
1080i
(1920x1080 30fps)
720p
(1280x720 60fps)
Uncompressed
SDTV
DV
MPEG2
480i
(720x480 30fps)
Bandwidth
Delay
1~1.5Gbps
100msec
20~80Mbps
1~2 sec
10Mbps
2~3 sec
250Mbps
100msec
30Mbps
~300msec
5~6Mbps
1~2 sec

The need for video compression is obvious based on the raw bandwidth needed for
HDTV and SDTV video types

While MPEG2 compression is widely adopted for SDTV broadcast applications, the
newer H.264 compression standard is preferred for higher bandwidth HDTV signals
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Standardization Organizations

ITU (International Telecommunication Union)
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VCEG (Video Coding Experts Group)
ISO (International Standardization Organization)
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JPEG (Joint Photographic Experts Group)
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MPEG (Motion Picture Experts Group)
HTTP
RTSP
ITU-T
ISO/IEC
H.261
H.263
H.264
MPEG-1 (11172)
MPEG-2 (13818)
MPEG-4 (14496)
RTP/RTCP
TCP
Transport stream
(13818-1)
UDP
IGMP
IP
PPP
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Ethernet
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Moving Pictures Expert Group (MPEG)

Committee of experts that develop video encoding standards

Until recently, was the only authority and “show in town”

Suitable for wide range of videos

Low resolution to high resolution
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Slow movement to fast action
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Can be implemented either in software or hardware
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The MPEG Concept

MPEG-1 video compression is based upon the same technique used in JPEG, but
includes techniques for efficient coding of a video sequence.
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Consider the video sequence displayed below:
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


The picture to the left is the first picture in the sequence followed by the picture in the middle and
then the picture to the right.
The video sequence shows a man running from right to left with a house that is stationary.
Using MPEG video, only the new parts of the video sequence is included together with
information of the moving parts
This applies only during the transmission of the video sequence to limit the bandwidth
When displayed it appears as the original video sequence again.
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Compression with Motion
Compensation
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Video contains a lot of spatial and temporal redundancy:
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Spatial redundancy and compression
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Neighboring pixels are similar
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Compresses each frame in isolation, treating it as a bitmapped image
Temporal redundancy and compression
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Adjacent frames are similar
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Compress sequences of frames by only storing differences between them

Performance can be improved by searching for just the right parts of the image to subtract
from the previous frame
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Motion Compensation (MC) based compression principle developed for H.261, is retained
in all later video compression standards.
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Spatial and Temporal Compression
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Spatial
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The compression of each frame is done with JPEG
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Each frame is a picture that can be independently compressed
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The Spatial compression engine looks inside each macroblock and determines what
information is absolutely necessary to maintain a visual reference

Subtle color shades will be removed to reduce the required storage space
Temporal

Certain frames are designated as Key frames
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Looks at the same blocks between pictures and uses prediction and motion estimation
algorithms to reduce the storage needed
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These predictions happen on Macroblock level
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Each frame between key frames is replaced by a “difference” frame

Difference frames only store the differences between the frame and the preceding frame
or most recent key frame
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MPEG Video Compression Standards
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MPEG-1
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MPEG-2
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Initial audio/video compression standard
Used by VCD’s
MP3 = MPEG-1 audio layer 3
Target of 1.5 Mb/s bit-rate at 352x240 resolution
Only supports progressive pictures
Current de facto standard, widely used in DVD and Digital TV
Ubiquity in hardware implies that it will be here for a long time
Transition to HDTV has taken over 13 years and is ongoing
Different profiles and levels allow for quality control
MPEG-4
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
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Includes support for AV “objects”, 3D content, low bit-rate encoding, & DRM
In practice, provides equal quality to MPEG-2 at a lower bit-rate
MPEG-4 Part 10 is H.264, which is used in HD-DVD and Blu-Ray
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MPEG Audio Compression Standards
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MPEG-1
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16 bits
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Sampling rate (32, 44.1, or 48kHz)
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Bitrate (32 to 320kbps)
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De facto - 44.1 kHz sample rate, 192 kbps bitrate
MPEG-2

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3 layers of increasing quality, MP3 (layer 3) being most common
Supports >2 channels, lower sampling frequencies, low bitrate improvement
AAC (Advanced Audio Coding)
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More sample frequencies (8 kHz to 96kHz)
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Higher coding efficiency and simpler filter bank

96 kbps AAC sounds better than 128 kbps MP3
Usually CBR, but can do VBR
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MPEG Video Compression Principle
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Relies on the eye's inability to resolve high frequency color changes
Uses redundancy within each frame and between frames
Discrete Cosine Transform, quantization & Huffmann coding predict a pixel value
from all adjacent pixel values, minimizing the overall bit rate
Intra-frames (I-frames) are generated from the process
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MPEG Structure

MPEG codes video in a hierarchy of layers
Video Sequence
I
P
B
B
B
P
B
B
P
Group of Pictures (GoP)
B
P
B
B
I
GoP Layer
Macroblock
Layer
Block Layer
(8x8 pixels)
Slice Layer
Picture Layer
(Frame)
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MPEG Frame Types
I-Frame (Intra Frame)
• Independent frame that is not related to any other frame.
• Independent of other frames and cannot be constructed from other frames.
• Intra-coded full image, very similar to the JPEG image, encoded with DCT, quantization, runlength coding and Huffman coding
P-Frame (Predicted Frame)
• Use delta encoding. The P frame refers to preceding I- and P-frames.
• Each P-frame contains only the changes from the preceding frame.
• DPCM encoded macroblocks, motion vectors possible.
B-Frame (Interpolated Frame)
• “Bi-directionally predictive coded pictures”, refers to preceding and succeeding frames,
interpolated the data and encodes the differences.
• Each B-frame is relative to the past and the future.
• A B-frame is never related to another B-frame
D-Frame
• "DC coded picture", only the DC coefficient of each block is coded (upper left-hand corner of the
matrix), e.g., for previews.
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Motion Compensation & Frame Types
Intra Frames (I-Frames)
• Contain full picture information. If errors occur, the decoder loses a frame
• Periodic transmission is essential
• Are the least compressed
Predicted Frames (P-Frames)
• Are predicted from the closest I or P frames
Bi-directional predicted frames (B-Frames)
• Offer the greatest compression
• Use past and future I & P frames for motion compensation
• Most sensitive to errors
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GOP (Group of Pictures)
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A set of consecutive frames that can be decoded without any other reference
frames
Starts with an I-frame and ends with the frame right before next I-frame
Consists of 12 or 15 frames typically
Transmitted sequence is not the same as the displayed sequence
The sequence of I, P and B frames is not standardized but can be chosen
according to the requirements of the application.
Arrows show prediction
dependencies between
frames
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Compression Standard/Rate Summary
Standard
Application
Bit Rate
JPEG
Continuous-tone still-image compression
Variable
H.261
Video telephony and teleconferencing over ISDN
P x 64kb/s
MPEG-1
Video on digital storage media (CD-ROM)
1.5Mb/s
MPEG-2
Digital Television
2-20Mb/s
H.263
Video telephony over PSTN
33.6kb/s
MPEG-4
Object-based coding, synthetic content, interactivity
Variable
JPEG-2000
Improved still image compression
Variable
H.264 /
MPEG-4 AVC
Improved video compression
10’s to 100’s kb/s
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MPEG-2 Profiles
MPEG-2 Profiles
Abbr. Name
Frames
YCbCr
Streams
Comment
SP
Simple Profile
P, I
4:2:0
1
no interlacing
MP
Main Profile
P, I, B
4:2:0
1
422P 4:2:2 Profile
P, I, B
4:2:2
1
SNR
SNR Scalable
Profile
P, I, B
4:2:0
1-2
SNR: Signal to Noise Ratio
SP
Spatial
P, I, B
Scalable Profile
4:2:0
1-3
HP
High Profile
4:2:2
1-3
low, normal and high quality
decoding
P, I, B
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The ISO/IEC specifications describe profiles that define the structure of the
encoded stream.

Profiles characterize the complexity of the encoding, indicating how difficult this
signal will be to decode.
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Digital Video Broadcast (DVB)
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Ever heard of DVB?

Digital Video Broadcast http://www.dvb.org/

European standard for digital video broadcasting, now used globally

DVB Project was launched in 1993 by an Industry-led consortium of over 250 companies
including broadcasters, manufacturers, network operators, software developers,
regulatory bodies and others

Project became operational in 1995

Based on MPEG-2 transport streams
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Very flexible and can carry Internet traffic

The standard also specifies mechanisms for interactive service with return channels
provided by PSTN, ISDN, GSM, DECT, LMDS, cable and satellite
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Digital Video Broadcast (DVB)

There are three major sub-standards of the DVB standard namely:
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DVB-S (Satellite) – using QPSK – 40 Mb/s

DVB-T (Terrestrial) – using QAM – 50 Mb/s
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DVB-C (Cable) – using QAM/OFDM – 24 Mb/s

The sub-standards differ only as it applies to physical representation, modulation,
transmission and reception of the signal.

DVB uses a MPEG-2 Transport Stream to carry it’s data and has added
some features in the MPEG-2 standard

Can deliver to the home almost anything that can be digitized:


High Definition Television (HDTV)
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Standard Definition Television (PAL / NTSC, SECAM)

New broadband multimedia data and interactive services
Several tables have been added to the MPEG-2 Transport Stream specifications
(CAT, EIT, etc.)
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Why does MPEG need DVB?

MPEG is primarily a compression standard.

The output from an MPEG encoder can be carried as an MPEG stream in a
noise free environment, but it is not suitable for a noisy channel.

DVB provides error correction, program information and conditional access
signaling, and modulation.

DVB guarantees the delivery of an MPEG stream over Cable (DVB-C), Satellite
(DVB-S), Terrestrial Radio Channel (DVB-T), or Local Microwave Distribution
Service (DVB-MC).
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Building the MPEG-2 Streams
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Two kinds of multiplexed stream are specified:


Transport Stream (TS)
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The transmission channel where errors occur

Designed for “lossy” links, such as networks or broadcast antennas

Consists of relatively short fixed-length TS packets
Program Stream (PS)
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Uses error-free transmission channels (storage e.g. disks)
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MPEG2 Transport Stream
Stream Type
Application
Features
Transport Stream (TS)
Used for transmission where
cell loss and bit errors occur.
Fixed-length packets (188 bytes)
Error correction is not included
in the MPEG standard.
Example: Broadcast
applications
A PES packet is divided up and
placed in the payload section of
TS packets.
Multiple reference clocks possible

The DVB stream consists of a series of fixed length packets which make up a
Transport Stream (TS).

Streams carry higher layer packets derived from an MPEG stream.

It carries multiple streams, some synchronized to each other (for lip sync), others
running independently.
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Transport Stream Packet
188 Byte Packet
4 Byte
Packet
Header
Adaptation Field
(if present)
Payload
(if present)

Fixed length of 188 bytes

First 4 Bytes are the packet header while 184 Bytes are used for payload

13 bit for the PID enable identification of 8192 (213) different kinds of logical channels

Packet contains data (video, audio, data, program guide)

Carries timing information (PCR)
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Every 4 Byte Header contains:




Sync byte 0x47
Transport error indicator
Payload unit start indicator
Transport priority
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


PID
Scrambling Control
Adaptation field control
Continuity Counter
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What do MPEG-2 TS Packets Carry?

Two main types of data packets (streams and sections):

Packetized Elementary Stream (PES)


Series of packets carrying video, audio and data streams
Data Section

Block of data with one or more TS payloads carrying program information and other data
Audio/Video MPEG-2 coding
PES Packet
PID 1
Data coding
Data Section
PID 2
Transport Stream
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MPEG-2 Transport Stream
188 bytes
Header
Sync
Byte
Bits
8
Payload
188 Bytes MPEG Packet
188 Bytes MPEG Packet
Transport
error indicator
Payload unit
start indicator
Transport
priority
PID
Transport
scrambling control
Adaptation
field control
Continuity
counter
1
1
1
13
2
2
4
Adaptation
Field length
Bits
8
Discontinuity Random access
indicator
indicator
1
Bits
Elementary stream
Priority indicator
1
5 flags
1
OPCR
Splicing
countdown
Transport private
Data
33 + 6 + 9
33 + 6 + 9
8
8+n
Bits 1
Adaptation
field
Optional
fields
Stuffing byte
5
PCR
Itw_valid flag
….….
Itw_offset
15
Reserved
2
Adaptation field
Extension flag
8+3+5+n
Piecewise_rate Splice_type
22
4
DTS_next_AU
3+1+15+1+15+1

Specified in MPEG-2 Part 1, Systems (ISO/IEC standard 13818-1)

Allows multiplexing of digital video & audio and synchronizing the output

Features error correction for transportation over unreliable media, and is used in
broadcast applications such as DVB and ATSC
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Program Specific Information (PSI)
Table Name
Standard
PIDs
Description
Program Association Table
MPEG
0x000
Associates program numbers with PIDs of
TS packets sending A Program Map Table
Program Map Table
MPEG
Spec’d in PAT
Specifies PID values of stream
configuring a program
Network Information Table
DVB
Spec’d in PAT
Physical network parameters e.g. FDM
frequency, transponder number
Conditional Access Table
MPEG
0x0001
Associates PID values and EMM stream
sending subscription details for charged
broadcasting
TS Description Table
MPEG
0x02
Associates descriptors and the entire TS
(application system)

A Transport Stream includes tables describing the relationship between the
programs and the elementary streams making up each program

A program can be identified by using a 16-bit program number
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Program Specific Information (PSI)
Tables
Their Purpose:
• act as a “table of contents” for the transport stream (TS)
• helps the decoder locate audio and video for each program in the TS
• Verifies Conditional Access (CA) rights
Consist of:
• Program Association Table (PAT) - 0x0000
• A root directory of the transport stream, providing the PID value for the packets
containing the PMT associated with each program.
• Conditional Access Table (CAT) – 0x0001
• Provides PID value for packets containing Entitlement Management Message (EMM).
EMMs update subscription options or pay-per-view rights per subscriber.
• Program Map Table (PMT)
• Lists PID values for packets containing a program’s video, audio, clock reference and
data components.
• Lists the PID value for each Entitlement Control Message (ECM) in the stream. ECMs
enable a decoder to descramble the audio, video and data for a program
• The Network Information Table (NIT)
• Provides information regarding a network on which various transport streams reside.
• This table is specified in MPEG-2 standard but defined in the DVB standard
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DVB Service Information (DVB-SI)
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
DVB-SI provides information to enable automatic configuration of the receiver to
demultiplex and decode the various streams of programs

Program Specific Information (PSI)

Program Association Table (PAT)

Conditional Access Table (CAT)

Program Map Table (PMT)

Network Information Table (NIT)
Additional Service Information

Bouquet Association Table (BAT)

Service Description Table (SDT)

Event Information Table (EIT)
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Running Status Table (RST)

Other tables: TDT, TOT, ST, SIT, DIT
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MPEG-2/DVB PID Allocation

PAT always has PID = 0 (zero)

CAT always has PID = 1

EIT always has PID = 18

PMTs have the PIDs specified in the
PAT

The audio, video, PCR, subtitle, etc.
PIDs for all programs are specified in
their respective PMT
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MPEG-2 PSI & DVB-SI Relationship
MPEG-2 PSI (Service Program Information)
Program
Association
Table
PID 0x00
PID 0xYY
PMT
Program
Map Table
CAT
Conditional
Access Table
PID 0x01
PAT
MPEG-2 PSI
locates the program
DVB SI (Service Information)
PID 0x10
NIT
PID 0x11
PID 0x11
Bouquet Association
Table
SDT
Service
Description Table
EIT
Event
Information Table
ST
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Network Information
Table
PID 0x13
BAT
PID 0x12
DVB SI selects the
program
TDT
Time and
Date Table
RST
Running
Status Table
TOT
Time
Offset Table
PID 0x14
Stuffing Table
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MPEG Clocks & Sync Mechanisms


Packet sync is performed by a unique value (Hex47) in the first byte of every packet.
Once packet sync is acquired:

The Sync byte ( 47HEX ) is extracted as timing reference and is used for generating the clock.

Decoder achieves sync after receiving 3-consecutive sync bytes

Only then can meaningful measurements on the PCRs be performed.
MPEG systems defines a Master clock and two decode time stamps:

Program Clock Reference (PCR):



Used to maintain the decoder’s clock in sync with the encoder’s clock
PTS/DTS:

Presentation Time Stamp – specifies when to present the access unit

Decode Time Stamp – specifies when to decode the access unit

Decoding and presentation take place when the decoder STC advances to the time
specified by the DTS and the PTS respectively

Both timestamps are found in the PES packet header
System Time Clock (STC)

27 MHz clock ± 810 Hz
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MPEG Header
Sync Byte

The Decoder must first identify the beginning of packets before it can interpret
the stream - it uses the Sync Byte field to do this!

The Sync Byte is always 0x47 (Hexadecimal) or 01000111 binary

The decoder looks for strings of zeros and ones which match the pattern of the
sync byte (see red below)
01010001111010010101101010001100011110010111000

Once the decoder finds a 0x47 in the stream, it looks 187 bytes down the stream,
and looks for another 0x47

If decoder finds three Sync Bytes in a row, then Sync is achieved and decoder
assumes packet boundaries from then on

Each packet is tested for 0x47 as soon as it arrives. If a packet arrives with an
incorrect sync byte, the decoder starts over. This is called SYNC LOSS
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MPEG Header
Continuity Counter

The continuity counter is a 4 bit field in the header which increments by 1 each
time a packet comes out on a specific PID:
All Packets PID 0x52
0

1
2
3
4
5
6
7
8
…
14 15
0
1
When a PID ‘skips’ one value of the continuity Counter, it is called a ‘Continuity
Error.’ This means one or more packets were lost.
All Packets PID 0x54
0
1
2
3
7
8
9
10
11
…
Continuity
Error Here
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PCR Encoding Process

Encoding process is driven by a 27MHz System Time Clock (STC)

Each program inserted into a TS contains a 27MHz timestamp (PCR)

Inserted by encoder/multiplexer in adaptation field every 40-100ms

PCR is a 42 bit field in the adaptation field of the Transport Stream (TS)

PCR field consists of a 9 bit part that increments at a 27MHz rate and a 33 bit
part that increments at a 90kHz rate (when 27MHz part rolls over)
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PCR Decoding Process

Decoding process is driven by a clock locked to the encoder's STC

Decoder uses the PCR to regenerate a local 27MHz clock

Decoder uses a Voltage Controlled Oscillator (VCXO) to generate a 27MHz clock

When received, the PCR is compared to a local counter which is driven by the
VCXO. Any difference is used to correct the frequency of the VCXO ensuring the
27MHz clock is locked to the PCR.

Decoders use PCRs to generate video timing, color burst, etc.
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ETSI TR 101 290 Recommendation

TR 101 290 recommends a set of syntax and information consistency tests that
can be applied to an MPEG-2 Transport Stream (TS)

The following assumptions and guiding principles were included when developing
these tests:


Mainly intended for continuous or periodic monitoring of an MPEG-2 TS in an operational
environment;

Primarily designed to check the integrity of a TS at source;

the general aim of the tests is to provide a "health check" of the most important elements
of the TS.
The tests are grouped into three tables according to importance;

The first table lists a basic set of parameters which are considered necessary to ensure
that the TS can be decoded.

The second table lists additional parameters which are recommended for continuous
monitoring.

The third table lists optional additional parameters which could be of interest for
certain applications.
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ETSI TR 101 290 Priority Groups

Baseband measurements are split into 3 groups:

1st priority (necessary for decodability)

2nd priority (recommended for continuous or periodic monitoring)

3rd priority (application-dependent monitoring)
3rd Priority
1st Priority
2nd Priority
No
Indicator
No
Indicator
No
Indicator
3.1
NIT_error
1.1
TS_sync_loss
2.1
Transport_error
3.2
SI_repetition_error
1.2
Sync_byte_error
2.2
CRC_error
3.3
Buffer_error
1.3
PAT_error
2.3
PCR_error
3.4
Unreferenced_PID_error
1.4
Continuity_count_error
2.4
PCR_accuracy_error
3.5
SDT_error
1.5
PMT_error
2.5
PTS_error
3.6
EIT_error
1.6
PID_error
2.6
CAT_error
3.7
RST_error
3.9
TDT_error
3.9
Empty_buffer_error
Data_delay_error
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DVB-C Transmitter & Receiver
Components
Multiplexed MPEG
Transport stream
Multiplexed MPEG
Transport stream
Mux
adaptation,
Energy
dispersal
Convolution
Interleaver
Byte to
multiple
conversion
Differential
encoding
Baseband
shaping
FIR filter
QPSK/QAM
modulation
RF
conversion
Differential
decoding
Matched FIR
filter and
equalizer
QPSK/QAM
demodulation
RF
conversion
Sync
inversion &
energy
dispersal
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Solomon FEC
Coder
Reed
Solomon FEC
decoder
Convolution
deinterleaver
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RX
Symbol to
byte mapping
42
CX380 CATV Analyzer
Testing MPEG-2 Systems with the CX380 MPEG Explorer option
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MPEG Network Overview
MPEG
Master Headend
IP Transport
Headends & Hubs
IP Network
Layer 2/3
Video QAM
HFC
Combiners
Service
router
Home
Coax Distribution
Network
CMTS
Inside Plant
Outside Plant

Per the DVB-C standard, MPEG-2 video is usually transported from Master Headend over fiber
using SONET/IP technologies that contain FEC or other error checking mechanisms.

At regional Headends/Hub sites, the MPEG-2 is extracted, QAM modulated, IF unconverted and
inserted into 6/8MHz channels for transmission over the HFC network to customer STBs.

The key impairments that can occur are caused by micro-reflections, non-linearity problems in the
network, and interference from adjacent analog channels (due to higher power levels).

MPEG-2 QoS testing will occur at the Master satellite Headend, or at any other point where the
Service Information is changed, and before insertion into the coaxial plant.
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Test Challenges & Advice

To start, there is no single, simple test solution

Terminology is new and confusing for those unfamiliar with digital video


The best known Test guideline is known as ETSI TR 101 290


Measurement guidelines for DVB systems
The ATSC has also recently introduced ATSC Recommended Practice:


Elementary Stream (ES), Packetized Elementary Stream (PES), Transport Stream (TS),
Program-Specific Information (PSI), etc.
Transport Stream Verification A78
Things to remember:

Fix Continuity Problems first. Continuity errors create bogus alarms in other areas. Until
you resolve the continuity problems, it will be very hard to determine if you have other
problems in your stream

The PAT is on PID 0x00. This is the first PID a decoder looks at – the MPEG ‘Base PID’
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SLM Measurements – RF Domain

Always check signal level & quality of QAM carrier/s

Without a good strong signal, analysis of the MPEG stream
may not yield any useful information

Check FEC counters and use Constellation diagram to
identify problems

Disable/enable Equalizer to check QAM decoder
performance, group delay and frequency response
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MPEG TS Summary

Displays number of programs detected on the MPEG-2 TS

Video, Audio, and Table statistics are provided for each program detected

Packet count associated with each is reported

Transport errors based on the transport error indicator in MPEG transport header
set
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Stream Summary

Reconstructing a program from all its video, audio, & table components requires
that the PID assignment is done correctly

Check consistency between PSI table contents and the associated video and
audio streams. This is one the main testing issue in MPEG.

PAT (Program Association Table) always appears in PID 0x0000

PMT (Program Map Table) - Identifies elementary streams in program, and gives
their PIDs.
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Stream Details

Statistics for each program are provided including video compression (SD or HD)

Verify PAT always appears in PID 0x00


Identifies MPEG-2 programs and gives PIDs for the PMT, Video and Audio.
CAT
(Conditional Access Table) & NIT (Network Information Table)
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Video Metrics
Perceptual
Note:
To simplify comparing video quality for
different service types, MPEG Explorer
includes both Absolute and Relative
MOS scores in its set of Video metrics

Absolute MOS-V


Relative MOS-V


1 to 5 score that considers picture & audio quality and the audio-video synchronization on the overall user experience.
VSTQ


A MOS score relative to the ideal for the particular codec and image resolution in use.
MOS-AV


Considers image resolution, frame rate, codec and compression level, transmission impairments, frame loss
concealment
Video Service Transmission Quality, a 0-50 codec-independent score (50 being best) measuring the ability of the IP
network to carry video reliably.
EPSNR

the estimated Peak Signal to Noise Ratio expressed in dB. This is an estimate of the distortion that has occurred
between the source video stream and the output video stream.
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Video Stream
Bandwidth Metrics
Note:
Using H.264 video compression,
the picture can be segmented into
sequences of macroblocks called
slices. The encoder can choose the
prediction style distinctly on each
individual slice (SI & SP frames)

Identifies I, P, and B frames in unscrambled and encrypted video streams

Bandwidth used by I, P, B, SI & SP video frames is analyzed to estimate the quantization level
applied by the video encoder

Average Bandwidth – Mean video bandwidth excluding IP overhead, FEC, & retransmissions

Max. Bandwidth - Peak video bandwidth excluding IP overhead, FEC, & retransmissions

SI-frames/slices: Facilitates switching between coded streams; contains SI macroblocks (a
special type of intra coded macroblock).

SP-frames/slices: Facilitates switching between coded streams; contains P and/or I macroblocks
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Video Stream
Frame Statistics

Detailed statistics for I, P, B, SI, SP frame types:

number of received frames and proportion of each frame type impaired by packet loss
and discard are reported

helps determine which GoP type and length should be used to obtain the best
performance from the video service

I/P/B/SI/SP Frames Impaired - proportion of applicable frames impaired by packet
loss/discard
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Video Stream
Frame Packet Results

To form an accurate assessment of quality of experience, it is necessary to know not only the
overall rates of packet lost or discarded, but also which frame types were affected.

MPEG Explorer reports detailed statistics for each frame type, including the number of received,
lost, and discarded I, B, and P frames and the proportion of each frame type impaired by packet
loss and discard.

These metrics can be useful for troubleshooting and can help determine which GoP type and
length should be used to obtain the best performance from the video service.

Packets Discarded - number of packets discarded by the jitter buffer due to late arrival.
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Audio Stream Metrics

MOS-A

Audio MOS, a 1-5 score that considers the effects of the audio codec, bit rate, sample
rate, and packet loss on listening quality.
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ETSI TR 101 290 Metrics
TR 101-290 Priorities

First priority:
 Sync, PAT & PMT, Continuity
 Decoder lock

Second priority:
 PCRs, CRCs, RF FEC
 Program Decode

Third priority: EPG
 PSIP

TS_sync_loss: Loss of synchronization at the MPEG transport layer

Sync_byte_error: Invalid MPEG transport sync byte

Continuity_count_error: Incorrect packet order, duplicate packet, or lost packet.

Transport_error: Transport error indicator in MPEG transport header set.

PCR_error: Discontinuity in program clock reference (PCR).

PCR_repetition_error: Time interval between two successive PCR values more than 40ms

PCR_discontinuity_indicator_error: Difference between two consecutive PCR values is over 100ms
without discontinuity bit set.

PTS_error: Interval between presentation timestamps more than 700ms.
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MPEG Explorer Test Summary

The MPEG Explorer provides a convenient and practical way to evaluate user quality
of experience levels using objective test data

MOS scores provide a familiar, intuitive representation of picture, audio, and overall
audiovisual quality

Metrics such as Relative MOS and VSTQ can be useful in accurately comparing
video quality across different service types

MPEG Explorer metrics are grouped into three layers:



Perceptual Quality Metrics
 High-level Quality of Experience (QoE) metrics that measure user's experience of the
service
Video Stream Metrics
 Relate to the encoded video stream, including image size, frame rate, GoP structure, etc.
Transmission Metrics
 Relate to the performance of the IP network, UDP/TCP and RTP/MPEG Transport protocols
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Thank you.
Any questions?
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