MPEG 101 Demyst Analysis & Picture Symptoms 20110808_opt.pdf

8/17/2019 MPEG 101 Demyst Analysis & Picture Symptoms 20110808_opt.pdf

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MPEG 101MPEG 101 – –Transport Stream DemystificationTransport Stream Demystificationby Leon Urban, Sr. Sales Engineerby Leon Urban, Sr. Sales Engineer

In collaboration with our Caribbean Value Added Reseller:

An LG Electronics Company

Mario Sebastiani & Bernard How


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Basic MPEG Building BlocksBasic MPEG Building Blocks



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Typical DTV Transport StreamTypical DTV Transport Stream

Special case of MPEG-2 transport stream

May contain multiple virtual channels

Video channels A video stream

Possibly one or more data streams

Audio channels

One or more audio streams

Possibly one or more data streams

-

One or more data streams

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MPEGMPEG--2 Transport Stream2 Transport Stream

Made up of 188-byte transport packets , each with 4byte header & 184 byte payload

ac pac e con a ns any n o n orma on–audio, video, data, PSI, …

OneOneTransport(MPEG)Packet

Transport(MPEG)Packet



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MPEGMPEG--2 Transport Stream (Contd.)2 Transport Stream (Contd.)

We say transport packets have multiple interleavedelementary streams -- audio, video, data, PSI, ...

ac e s e ong ng o e same e emen ary s ream are

identified by packet id (PID) in packet header (samecolor in our illustrations).

MPEG-2 Transport Stream

These three packets are the same color.They have the same PID and belong to


.


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MPEGMPEG--2 Transport Stream2 Transport Stream – – Header FieldsHeader Fields

Noteworthy fields:

1) Sync Byte – Find packet boundary

2) PID – Used while demultiplexing stream3) Continuity Counter – Identify packet loss

4) PCR stamp in adaptation field – Clock sync

Header (4 Bytes)


Adaptation

Field

Continuity

Counter

Sync

BytePID

PES 1

Adaptation

Field

(Optional)

PIDSync

ByteContinuity

Counter PES x

Or other Payload (Pat, PMT, PSIP,

etc)……………………………...



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MPEG Header Fields: Sync ByteMPEG Header Fields: Sync Byte

When a decoder first tunes, all it sees are a stream of0’s and 1’s

e eco er mus rs en y e eg nn ng o

packets before it can interpret the stream

01010001111010010101101010001100011110010111000

MPEG Data Prior toPacket Sync



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MPEG Header Fields: Sync Byte (Contd.)MPEG Header Fields: Sync Byte (Contd.)

he Sync Byte of a packet is always 0x47(Hexadecimal) or 01000111 binary

The decoder looks for strings of zeros and ones whichmatch the pattern of the sync byte (see red below)

010100011101000111101001010110101000010001110100011111000111



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Once the decoder finds a 0x47 in the stream, it looks 187 bytesdown the stream, and looks for another 0x47

If it finds three S nc B tes in a row then the Decoder has Found

Sync and assumes packet boundaries from then on Each packet is tested for 0x47 as soon as it arrives. If a packet

, .is called SYNC LOSS

Found Sync

0x470x47 187 bytes187 bytes 0x470x47 187 bytes187 bytes 0x470x47 187 bytes187 bytes Packet 188 bytesPacket 188 bytes0x47 187 bytes 0x47 187 bytes 0x47 187 bytes Packet 188 bytes

Sync Not Found

0x320x32 1101010101011101101010101000111010101010111011010101010001Packet 188 bytesPacket 188 bytes Packet 188 bytesPacket 188 bytes 0x32 11010101010111011010101010001Packet 188 bytes Packet 188 bytes



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If you don’t have Packet Sync, the decoder cannot findpacket boundaries. You will not be able to decode at

Packet Sync problems typically occur in hardware atpacket boundaries during format converters, edgedevices, demodulators etc:

ASI to Gig-E

ASI to Microwave or QAM

Satellite to ASI



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PIDs DefinedPIDs Defined -- ATSC Bitstream ATSC Bitstream

PSIP TablesPATPAT

PMTPMT

VideoVideo

AudioAudioPAT

PMT

Video

Audio

PSIP Generator

Data channel

Data-

Null Null

PSIPPSIP

Null

PSIP

Data Server

Data Server

Video Encoder

Audio Encoderenhanced

Audio/Video

channel

u -

plexer

Audio Encoder

Video Encoder

Audio/Video

channel




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PIDs DefinedPIDs Defined -- Digital Cable BitstreamDigital Cable Bitstream

PAT

PMT

Null

Video

Audio

Video Encoder

u o nco erVideo/Audio

channel VideoAudio

Video/Audiochannel

CAT

Video Encoder

Audio Encodereo

AudioVideo

Audio

Video Encoder

Audio EncoderVideo/Audio

channel

u -

plexer

Audio Encoder

Video Encoder

Video/Audio

channel




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MPEGMPEG--2 PSI Tables (Contd.)2 PSI Tables (Contd.)

Decoder: Receiver or

Set top Box

“WXXX Channel Video”

PID 0x31 Program 1

“WXXX Channel Audio”

PID 0x34 Program 1

PSI via PID assignments and descriptors tells the decoder that these PIDS go

to ether to make u a ro ram



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Transport Stream DemultiplexingTransport Stream Demultiplexing

When a set top box first receives a Transport Stream, itdemultiplexes that stream based on PID


set top box

Program Program Program Program

Program02 Audio Program

PSIP

PAT/PMT/MPEG


eo 02 Video 03 Video u o

Tablesa es


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MetadataMetadata

Data about included data is metadata

are contained in each PID, and which PID’s gotogether.

There are two kinds of Metadata

Program Specific Information (PSI) - Tables in thestream defined in the MPEG standards

Program and System Information Protocol (PSIP) -



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MPEG 101 Knowledge Check #1MPEG 101 Knowledge Check #1

:: HowHow manman ofof whatwhat must the decodermust the decodersee before it can begin decoding a digitalsee before it can begin decoding a digital

video stream ?video stream ?



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PSI Data In the StreamPSI Data In the Stream



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PSI Tables (MPEGPSI Tables (MPEG--2 Tables)2 Tables)

PAT - Program Association Table

A ears in PID 0x0000

Identifies MPEG-2 programs in transport stream and givesPIDs for their PMTs

e s on x . s s e rs or ase aMPEG decoder looks for

PMT - Program Map TableIdentifies elementary streams in program (virtualchannel and ives their PIDs.



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PMT 1Video PID 0x31

Audio PID 0x34

Audio PID 0x35PCR_PID 0x31

PMT 2Video PID 0x41

Audio PID 0x44

Audio PID 0x45

PAT (always on PID 0x0)

Station TSID

PMT 1 -> On PID 0x30

PID 0x40

_

PMT 3Video PID 0x51

-

PMT 3 -> On PID 0x50

Audio PID 0x55PCR_PID 0x51



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Graphical View of PAT/PMTGraphical View of PAT/PMT

Elementary streamsfound in this PMT

Elementary streams

DescriptorDefines

AdditionalStream

Characteristics

(PID 0x0000)

Program 2PID for Program 3

PID for

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PMT

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Set top Box

“ WXXX Channel Video”

PID 0x31

“ WXXX Channel Audio”

PID 0x34

PSI

PID assignments


ese go oge er


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PSIP Data In the StreamPSIP Data In the Stream



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PSIP BackgroundPSIP Background

Program and System Information Protocol

Metadata inserted into broadcast stream

Enables: Tuning to virtual channels

Displaying channel name (on channel changes)

Interactive electronic program guides (EPGs)

Caption decoding

“V-Chi ” function arental content blockin

Accurate receiver time-of-day clock setting

Redistribution Control

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Basic functions of PSIP TablesBasic functions of PSIP Tables

BrandingBranding – Station call letters and channel number

– - ,

Video PID’s, Virtual Channel Table

Announcement Announcement – Electronic Program Guide (EPG)



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Signaling vs AnnouncementSignaling vs Announcement

SignalingSignaling

Information about what is "on now"

Used to assemble program elements into whole

Provides linkages

Ex: PMT and/or VCT used to link different components of televisionprogram (i.e. video and audio)

Used to define characteristics of current program (descriptors0

Captioning, ratings, redistribution…

Announcement Announcement Information about what will be available in the future

Program Guide information (name, description schedule)

Characteristics of future ro rams ca tionin ratin s

redistribution…) Typically does not provide linkages between program elements



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PSIP Generation ArchitecturePSIP Generation Architecture

Encoder(s)

Traffic/Program

System

Traffic/Program

System

Traffic/Program

System

PSIPPSIPPSIPM

TimeTimeTime

RemoteRemoteRemoteGenerator Generator Generator

X Automation

System

Automation

System

Automation

System

GUI(s)GUI(s)GUI(s)

ListinListinListin StagingStagingStaging

F

I

R

E

ServiceServiceService Server Server Server W AL

L



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PSIP metadata found in the ‘Payload’ PSIP metadata found in the ‘Payload’

Noteworthy fields:

Payload contains PSIP, PAT, PMT metadata


PSIPmetadata

found in the

packet ‘Pa load’

Adaptation

Field

Continuity

Counter

Sync

BytePID

188 Bytesea er y es

PES 1

Adaptation

Field

(Optional)

PIDSync

ByteContinuity

Counter PES x


etc)……………………………...



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ATSC PSIP Tables ATSC PSIP Tables

MGT - Master Guide Table Interval: 150msInterval: 150ms- Appears in PID 0x1FFB.-

tables (except STT). A directory of all PSIP tables.

- ys em me a e n erva : , ms secn erva : , ms sec- Appears in PID 0x1FFB

- Gives current UTC time.

VCT - Virtual Channel Table Interval: 400msInterval: 400ms- .



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ATSC PSIP Tables (Contd.) ATSC PSIP Tables (Contd.)

RRT- Rating Region Table Interval: 60,000ms (1 min)Interval: 60,000ms (1 min)- Describes content advisory system(s) being used to rate

EIT - Event Information Table

EIT has variable intervals:EIT has variable intervals:

EITEIT--0: 500ms0: 500msEITEIT--1: 3,000ms1: 3,000msEITEIT--2 & u : 60 000ms2 & u : 60 000ms

- Gives titles, start times, durations, content advisoryratings of events (TV programs).

ETT - Extended Text Table Interval: Follows it’s EITInterval: Follows it’s EIT- Gives extended textual descriptions of virtual channels

and events.



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PIDs in the StreamPIDs in the Stream

PAT points

to PMT

PATpoints

toPMT

metadatatables: VCT,MGT, STT,

EITs & ETTs



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Details of FCC R&ODetails of FCC R&O – – PSIP relatedPSIP related

"…fully implement PSIP to the extent that ATSC A/65Brequires."

MGT, TVCT, EIT-0

3, STT, RRT (except region 1) Required tables and descriptors must be populated

w proper an correc n orma on

At least 12 hours of populated EITs (EIT-0 thru 3)

Each EIT contains 3 hours worth of event information

Ma or channel rules from PSIP A 65B ado ted

Correct Major Channel number must be used

Correct TSIDs (Transport Stream ID) must be used



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VCT VCT ---- Virtual Channel Concept Virtual Channel Concept

Breaks the link between RF channel number and user’snotion of channel number

Analog broadcast “channel number” was the same as the

RF carrier designation

“ ”

Channel Table ( VCT)

One digital TS can include multiple channels ofprogramm ng

8-VSB carrier freq. may have (probably) shifted during



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VCT: Two Part Channel Numbers VCT: Two Part Channel Numbers

1st part: “major channel” (Original analog channel)

2nd part: “minor channel”

Broadcasters retain their brand identity

Digital services groupable with analog

KZZZ has been associated with Channel 7 for years; KZZZ-DTcan be found on Channel 7-1



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Virtual Channel Table (VCT) Virtual Channel Table (VCT)

Has same info as PAT & PMTs, plus more.

Allows tuning by virtual major-minor channel number,ra er an p ys ca c anne num er an -

“program” number.

.

Allows channel name to be displayed on channel

chan es and in EPG.

ATSC receivers are designed to use VCT; may havetrouble with PAT and PMTs alone.



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Comparing PAT vs. VCTComparing PAT vs. VCT

rogram ssoc a on a eTable IDSection Syntax IndicatorSection LengthTrans ort Stream ID TSID

r ua anne a eTable IDSection Syntax IndicatorSection LengthTransport Stream ID (TSID)

Version Number

Current Next IndicatorSection NumberLast Section Number

Version Number

Current Next IndicatorSection NumberLast Section Number

Program Map PID

Number of Channels in SectionShort NameMajor Channel Number

Minor Channel NumberModulation ModeChannel TSIDProgram NumberExtended Text Message Location

Descriptor ( )Source IDService Type Access Controlled


en e u e

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Virtual Channel Table (VCT) Virtual Channel Table (VCT)

Virtual Channel

• or anne ame

• Major Channel Number

• Minor Channel Number

• Modulation Mode

• requency

• TS ID (of Virtual Channel)

• Program Number (in Stream)

• Extended Text Location• ccess on ro e

• Hidden ? Hide from Guide?

• Service Type (A/V/D)

• Source ID

Video Stream

Eng Audio Stream• erv ce oca on escr

• other descriptors Fre Audio Stream(PID 0x1FFB)



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PSIP and PSI Link PSIP and PSI Link

Table Information for a

Television Broadcast Stream

PMT 1(On PID 0x30)Video PID 0x31

PAT(On PID 0x0)

Station TSID

VCTOn Pid 0x1FFB

4-1

PCR_PID 0x31PMT 1 -> On PID 0x30 Video PID 0x31

Audio PID 0x34

PAT and PMT Tables PSIP table



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Continuity CounterContinuity Counter



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Q: Name two tables found in PSIQ: Name two tables found in PSI



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MPEG Header: Continuity CounterMPEG Header: Continuity Counter

he continuity counter is a 4 bit field in the headerwhich increments by 1 each time a packet comes outon a s ecific PID:

0 1 2 3 4 5 6 7 8 14 15 0 1……

All Packets PID 0x52

When a PID ‘skips’ one value of the continuity Counter,

we call it a ‘Continuity Error.’ This means one or morepackets were lost.

All Packets PID 0x54

ContinuityError Here

0 1 2 3 7 8 9 10 11 ……



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MPEG Header: Continuity Counter (Contd.)MPEG Header: Continuity Counter (Contd.)

Identifies WHEN we lose

Packets, but not HOW MANY!

Packet loss causes many other kinds of analysis to ‘reset’ or give

bogus results. Any analysis based on an average over many packets will

automatically reset when it encounters continuity problems.

‘ ’

frequent continuity errors should be one of the FIRST things youlook for when debugging.



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Three Things to RememberThree Things to Remember

hree main monitoring and troubleshooting lessons:

Fix Continuity Problems first

on nu y errors crea e ogus a arms n o er areas.

Until you resolve the continuity problems, it will be very hard todetermine if you have other problems in your stream

o Be Discussed

To Be Discussed



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given PID changes from 3 to 7, howgiven PID changes from 3 to 7, how



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Elementar streams:Elementar streams:Encoding Video & AudioEncoding Video & Audio


MPEGMPEG 2 / MPEG2 / MPEG 4 Video Compression4 Video Compression


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MPEGMPEG--2 / MPEG2 / MPEG--4 Video Compression4 Video Compression

Digital Compression starts at the MPEG encoder

MPEG2 or MPEG4 CODECS can be carried in an MPEG2 Transport Stream

The encoder filters noise in the input signal and: compresses baseband video & audio OR

uncompressed digitized video/audio/data (SDI)

Video and Audio elements are encoded into a sequence of frames

A frame is a single image from a video or audio sequence

In most countries, one frame occurs every 33 milliseconds

Each frame is encoded in one of three ways:


MPEGMPEG 2 Video/Audio Encoding2 Video/Audio Encoding


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MPEGMPEG--2 Video/Audio Encoding2 Video/Audio Encoding

I Frames

I-picture: intra-picture encoding, similar to jpeg encoding(exploiting spatial redundancy).

Compressed solely on information found in the frame

Highest amount of data of all other frame types

‘ ’

B & P frames are calculated from the I frame

“I” stands for “Intra” coded

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B Frames

B-picture : bi-directional encoding, using motion adjusteddeltas from a previous and a future frame (exploiting temporal.

Uses Data from preceding and following I & P frames

De ends on data before and or after in video se uence

Cannot calculate from another B frame




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P Frames

P-picture : predictive encoding, using motion adjusted deltasfrom a revious reference frame ex loitin tem oralredundancy).

Compressed using data from closest preceding I or P frame

w ac - o- ac rames usua y n ca e as mo on




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Encoder emits sequence of encoded frames

Sizes of encoded frames var

Encoded frames are packed into packetizedelementary stream (PES) packets.

PES packets are packed into MPEG-2 transport packets(All packets for single video stream have same PID

Overall compression ratio is 50:1 or more

ose cap on ng assoc a e w v eo rame sencoded here


MPEG 2 Elementary Stream


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MPEG-2 Elementary Stream

PTSDTS

PES Packet

Pa loadPES

Header

PES Packet

Pa loadPES

Header

PES Packet

Pa loadPES

Header

Only PTS on Audio PES

packet

MPEG-2 Elementary Stream

Adaptation

Field

Continuity

Counter

Sync

BytePID

188 BytesHeader (4 Bytes)

PES 1

Adaptation

Field

(Optional)

PIDSync

Byte

Continuity

Counter PES x


etc)……………………………...

Optional

FieldsLength Flags

Stuffing

Bytes Adaptation Field on Video

PID’s Only

PCR

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Group of Pictures = GOP

Series of frames consisting of a single ‘I’ frame with P & B frames A GOP be ins with an ‘I’ frame and ends with last frame before the

next ‘I’ frame

All frames within the GOP depend directly or indirectly on data from

Relationships between GOPs: Either OPEN or CLOSED

Closed GOP is self-contained. No dependance on data outside GOP

Open GOP can use data from I frame of following GOP

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MPEGMPEG--2 Video/Audio Encoding (Contd.)2 Video/Audio Encoding (Contd.)


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MPEGMPEG 2 Video/Audio Encoding (Contd.)2 Video/Audio Encoding (Contd.)

Example 1. Panning CameraI-picture B-picture I-picture

Exam le 2. Movin Ob ect B-picture I-pictureI-picture




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ypica P tructuresP Frame83.45 Kb

I Frame216.6 Kb

B Frame.

Typical low motion GOP sequence

P Frame44.5 Kb

183.2 Kb

P Frame59.9 Kb

P P P P P PIP P P P P P P P P P P P P PP P P

Typical high motion GOP sequence


ATSC/SCTE Audio Formats ATSC/SCTE Audio Formats


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SC/SC ud o o atsSC/SC ud o o ats

ATSC uses AC-3 audio encoding, with up to 6 audiochannels: left, right, center, left surround, right

The full set is often called 5.1 audio. .

The encoded bit rate may be up to 384 kbps.


ACAC--3 Audio Encoding3 Audio Encoding


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AC AC 3 Audio Encoding3 Audio Encoding

Audio frames, each 32 milliseconds in length, areencoded.

nco e rame s ze epen s on y on ra e.

Encoded frames are packed into packetized.

PES packets are packed into MPEG-2 transport packets.

All ackets for sin le audio stream have same PIDvalue.)




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-- ,,are the three video frame typesare the three video frame types



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Video and Audio Video and AudioSyncronization usingSyncronization using


Audio Audio--Video Synchronization Video Synchronization


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ud oud o deo Sy c o at odeo Sy c o at o

Audio video are encoded inde endentl must besynchronized during play

MPEG has to allow for great distances AND networkprocessing between the Encoder and Decoder and still


How to Assure Audio/Video Sync?How to Assure Audio/Video Sync?


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/ y/ y

In order for the audio and video Elementary Streams to,

Clock must remain in sync

he next few slides will demonstrate how this ha ens and what components to check when it fails…


Encoder Inserts PCREncoder Inserts PCR


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When the encoder streams creates packets, it embedsthe current value of it’s 27 MHz clock into the stream

s me re erence s ca e e : rogram oc

Reference

stream every 100ms

Encoder27Mhz Clock

MPEG Packets

MPEGPacket withPCR Stamp


The Encoder and Decoder Clock The Encoder and Decoder Clock


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he MPEG encoder and MPEG decoder use a 27Mhz ‘clock’ to encode/decode incoming audio and video

e c oc s ac ua y a coun er w c a vances every

1/27000000 seconds

Encoder

27Mhz Clock

Encoder

27Mhz Clock

Encoder

27Mhz Clock

Decoder

27Mhz Clock

Decoder

27Mhz Clock

Decoder

27Mhz Clock

1,2,3,4…..1,2,3,4…..1,2,3,4….. , , , ….., , , ….., , , …..




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1/27000000 seconds

Encoder

27Mhz Clock

Encoder

27Mhz Clock

Encoder

27Mhz Clock

Decoder

27Mhz Clock

Decoder

27Mhz Clock

Decoder

27Mhz Clock

1,2,3,4…..1,2,3,4…..1,2,3,4….. , , , ….., , , ….., , , …..




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1/27000000 seconds

Encoder

27Mhz Clock

Encoder

27Mhz Clock

Encoder

27Mhz Clock

Decoder

27Mhz Clock

Decoder

27Mhz Clock

Decoder

27Mhz Clock assive

Network

Processing

1,2,3,4…..1,2,3,4…..1,2,3,4….. , , , ….., , , ….., , , …..


PCR Timestamp IssuePCR Timestamp Issue


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What could conceptually cause PCR timestamp issues?

Enco er possi y time stampe incorrect y

PCR packet was accidentally lost in transmission

When PCR time stam s o awr , we have “PCR itter”


PCR Jitter DefinedPCR Jitter Defined


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PCR Jitter is:

Difference between

the Actual Value of the PCR time stamped byn r

and

e xpec e a ue o e as ca cu a e ydecoder based on the clock rate and the time

.

PCR Jitter spec: 500ns


PCR Rate (Frequency) OffsetPCR Rate (Frequency) Offset


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PCR Frequency Offset is:

Difference between

the clock frequency calculated at decodern l P R v l r iv

and

an ea z c oc , w c s e c oc ra edictated by the MPEG-2 standard

PCR Frequency Offset Spec: +/- 810 Hz


PCR Intervals, Jitter and RatePCR Intervals, Jitter and Rate


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PCR spec summary:

Transmit interval: 100 ms

Jitter: no more than 500 ns

Rate: 27 MHz +/- 810 Hz

Most streams seen in the field are com liant but evernow and then extreme jitter shows up.

Here’s Why


PCR Packet SpacingPCR Packet Spacing BeforeBefore MuxingMuxing


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Note the Number of Packets between each PCR packetin each Input Stream

Video 0x31

Video 0x41

Spacing

0x31 2 Packets

TransportStream

Video 0x510x41 1 Packet

0x51 0 Packets


PCR Packet SpacingPCR Packet Spacing After After MuxingMuxing


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Note that the PCR packet spacing has changed!

Video 0x41 TransportStream

MUX

0x31 2 Packets 8 Packets

0x41 1 Packet 5 Packets

Video 0x51

0x51 0 Packets 2 Packets


Muxing Causes PCR JitterMuxing Causes PCR Jitter


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When we MUX multiple streams together, thespacing between the PCR packets in each

as well, throwing the time stamps off

The TEMPORAL shift in PCR values is referredto as “ PCR jitter ”


Muxing Causes PCR Jitter (Contd.)Muxing Causes PCR Jitter (Contd.)


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he MUX has to RESTAMP all the PCR valuesto correct for the change in the packet –

The more services on the output, the harder it is torestamp

‘ ’ ,is to restamp


PCR Timestamp Issue (Contd.)PCR Timestamp Issue (Contd.)


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What in your network facility could cause PCRtimestamp issues?

ree o e mos common are:

It can happen at the source encoding

It can happen on any IP link – due to network lag


PCR Jitter From Incorrect EncodingPCR Jitter From Incorrect Encoding


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If the MPEG encoder’s parameters are set upincorrectly, you can introduce jitter at the source

s s re a ve y rare, owever

If a national programmer sent it’s stream up to the bird withitter in it, the result would effect all receive sites !

Re-encoded streams at the headend may also create PCR jitter

Local broadcast streams could create PCR jitter at the encoder


PCR Timestamp Issue (Contd.)PCR Timestamp Issue (Contd.)


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What in your network facility could cause PCRtimestamp issues?

ree o e mos common are:

It can happen at the source encoding

It can happen on any IP link – due to network

ag


PCR Jitter Due to IP CarriagePCR Jitter Due to IP Carriage


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Network lag can conceal MPEG jitter problems on an IPlink. The network jitter is usually so much larger than ‘ ’

Hopefully, the IP- ASI or IP-QAM edge device willprov e u er ng an use g eve ma o smooout the network lag.

MT-40 provides a way to separate the Network Lagfrom PCR Jitter.




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Q: What is the key element forQ: What is the key element for

time sync?time sync?



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Video and Audio Buffers Video and Audio Buffers& Presentation Time& Presentation Time


Presentation Time StampPresentation Time Stamp -- PTSPTS


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Each Frame is marked with a PTS – “Presentation TimeStamp” – a positive number

e va ue o e s se o e va ue o e nco er

Clock when the frame is encoded

MPEG Packets

Encoder

27Mhz Clock

1,2,3,4…..

F1PTS500

F2PTS950

Packetizer


Packets Assigned to Decode BufferPackets Assigned to Decode Buffer


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As packets flow into the Decoder, a space in memory isset aside for them, one buffer for each PID.

MPEG Packets

27Mhz Clock 27Mhz Clock 27Mhz Clock

1,2,3,4…..1,2,3,4…..1,2,3,4…..

Buffer 1 Pid 0x31 Video

Buffer 2 Pid 0x34 Audio


Reconstruction of Frames From BufferReconstruction of Frames From Buffer


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Packets form Video and Audio Frames in the buffer

MPEG Packets

27Mhz Clock 27Mhz Clock 27Mhz Clock

1,2,3,4…..1,2,3,4…..1,2,3,4…..


F1PTS500

F2PTS675

F3PTS950


F1PTS

F2PTS


The Magic of DecodeThe Magic of Decode


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When the value of the Decode clock MATCHES the PTSon the frame, that frame is sent to the decode

MPEG PacketsF1

DecodeHardware27Mhz Clock 27Mhz Clock 27Mhz Clock

PTS200

= 200= 200= 200


F1PTS500

F2PTS675

F3PTS950


F2PTS


Another Frame Goes to Decode Hardware Another Frame Goes to Decode Hardware


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Next Frame

MPEG PacketsF1


500

= 500= 500= 500


F2PTS675

F3PTS950


F2PTS


One More Frame Heads to DecodeOne More Frame Heads to Decode


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And the next frame…

MPEG PacketsF2


675

= 675= 675= 675


F3PTS950


F2PTS


Audio and Video Buffers Audio and Video Buffers


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Receiver must buffer audio and video frame data untilpresentation time.

a a appears oo a e n e ranspor s ream, u er

underflow results. ,

buffer overflow results.

Either condition results in arbled la or incorrectsynchronization.

Different set top boxes may respond differently to thesame underlying buffer violations


Summary: Audio/Video SyncSummary: Audio/Video Sync


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PCR values help the Encoder Clock and the DecoderClock to remain in sync

er can cause sync ron za on pro ems or

elementary streams

PCR jitter and frequency offsets are within standard limits

Elementar stream buffers limits are NOT violated

Large PCR jitter values can cause “Lip sync” error

Buffer over- or underflow roblems ma cause “tilin ”

“pixelization”/”macroblocking” errors




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Q: What is one potential result ofQ: What is one potential result of “video buffer underflow” ? “video buffer underflow” ?



h i i i d bl h i l


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hree main monitoring and troubleshooting lessons: Fix Continuity Problems first

on nu y errors crea e ogus a arms n o er areas

Until you resolve the continuity problems, it will be very hard todetermine if you have other problems in your stream

Check for PCR jitter

PCR jitter can cause packet over- or underflow problems

To Be Discussed



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rou es oo ngrou es oo ng

usin the MTusin the MT--4040


Why Transport Stream Analyzer?Why Transport Stream Analyzer?

With l t i i if di / id did t h


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With analog transmission, if audio/video did not haveany anomalies on a TV set up in the studio, it would’

For digital transmission, this assumption is NOT validas g a s gna s re y on e eco er s

Firmware implementation

Software decoding capability


Why Transport Stream Analyzer? (Contd.)Why Transport Stream Analyzer? (Contd.)

he t ansition to digital has int od ced some specific


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he transition to digital has introduced some specificchallenges for broadcast engineers

• Not all Set top boxes will respond the same way to the same

underlying problem

• Standards violations in digital Transport Streams may show up on a

rece ver on y nterm ttent y

The only streams which will consistently decode are

those which are com liant The best way to assure compliance is with a Transport

stream Analyzer/Monitor


Troubleshooting ExampleTroubleshooting Example – – Audio Outage Audio Outage

Customer calls into station or NOC audio dropping out on their set


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Customer calls into station or NOC – audio dropping out on their set

In station video monitors & set top boxes do not have any problems

How serious is this problem? Are other Customers seeing it?

EncodersEncoders

EncodersEncoders

Satellite

Satellite

Dish

QPSK ReceiversSate iteReceiversSatellite

Receivers

PSIP Gen

MUXProcessing

Modulator

Digital to Analog Mod

Data Gen

Cable TV Scenario


Troubleshooting Example (Contd.)Troubleshooting Example (Contd.)

Start at the end Off air or combined RF output


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Start at the end…..Off-air or combined RF output….

EncodersEncoders

EncodersEncoders

Satellite

ASI

Satellite

Dish

QPSKReceiversSate ite

ReceiversSatelliteReceivers

PSIP Gen

MUXProcessing

Modulator


ASI

ASI

Gigabit-IP

Data GenCable TV Scenario

Transport Stream Analyzer

RF Input (8VSB or QAM)



Check of the MPEG analyzer shows Standards violation has occurred


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Check of the MPEG analyzer shows Standards violation has occurred



Move back in the network toward the beginning


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Encoders

Move back in the network toward the beginning.... Input to the QAM modulator………

EncodersEncoders

Encoders

Satellite QAM

ASI

Gigabit-IP

Satellite

Dish



PSIP Gen

MUXProcessing


ASI

ASI

Data Gen EthernetInput




Standards violation is still present


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Move further back


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Encoders

Move further back…..

EncodersEncoders

Encoders

Satellite

ASI

ASI

Satellite

Dish



PSIP Gen

MUXProcessing

Modulator


ASI

ASI

Gigabit-IP

Data Gen ASIInput






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And further back ..


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And further back…..

EncodersEncoders

EncodersEncoders

Satellite

ASI

Satellite

Dish



PSIP Gen

MUXProcessing

Modulator


ASI

ASI

Gigabit-IP

Data Gen

Cable TV Scenario

ASIInput




Using record capability to collect data…..


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Encoders

Using record capability to collect data…..

EncodersEncoders

Encoders

Satellite

ASI

Gigabit-IP

Satellite

Dish



PSIP Gen

MUXProcessing

Modulator


ASI

ASI

Data Gen

Cable TV Scenario

Record at

Record atthis point



Summary: MPEG Monitoring Over the Long TermSummary: MPEG Monitoring Over the Long Term

Complete and continous monitoring…..


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Encoders Broadcast Scenario

Complete and continous monitoring….. Analyze, Monitor or

Record Streams at any

EncodersEncoders

Encoders

Satellite

TelevisionTransmitter

ASI

ASI

Gigabit-IP, ASI or

SMPTE 310

of these points

Satellite

Dish



PSIP Gen

MUXProcessing

QAMModulator

ASI

Gigabit-IP

Data Gen Digital to Analog Mod

Cable TV Scenario

Transport Stream Analyzer or

Remote Monitor

RF Input (8VSB or QAM)Error Alerts:

SNMP,SMS,E-Mail,Tri ered Recordin or

ErrorNotification


Contact Closure


hree main monitoring and troubleshooting lessons:


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g g Fix Continuity Problems first

on nu y errors crea e ogus a arms n o er areas

Until you resolve the continuity problems, it will be very hard to

determine if you have other problems in your stream

Check for PCR jitter

PCR jitter can cause packet over- or underflow problems

Move Backward through your network as you debug

Isolate the offending device first, then go for detailed problemso v ng s eps recor ng a e, e c.


Summary: MPEG’s 7 Basic ParametersSummary: MPEG’s 7 Basic Parameters

Per ATSC standards:


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PAT Interval: 100ms

PMT Interval: 400ms

PCR Interval: 100ms

Max Jitter: 500ns

Max Freq. Offset: +/- 810 Hz

Also check:

Video Buffer

Audio Buffer


ReferencesReferences

Information Technology -- Generic Coding of Moving Pictures and Associated Audio Information: Systems (MPEG-2 Systems


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y ( y

standard , ISO/IEC 13818-1.

ATSC Digital Television Standard , ATSC Doc. A/53.

Program and System Information Protocol for TerrestrialBroadcast and Cable , ATSC Doc. A/65 (with amendments).

ATSC Data Broadcast Standard , ATSC Doc. A/90.

.

Video Over IP by Wes Simpson – available SCTE bookstore.


In the Caribbean:


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Mario Sebastianimsebastiani incos ec.com

Bernard How

[email protected]

s our a ue e e-se er n eCaribbean for Triveni Digital products

Stream Scope:

•MT-40 MPEG analyzer

•RM-40 MPEG monitor GuideBuilder – PSIP metadata generator


- --

Thank you-Gracias-Merci-Danki …


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Caribbean Cable Television Association San Juan, Puerto Rico

August 17, 2011

MPEG 101MPEG 101 – –Transport Stream DemystificationTransport Stream Demystification


MPEG 101 Demyst Analysis & Picture Symptoms 20110808_opt.pdf

Documents