Monitoring and Troubleshooting MPEGProblems in a Broadcast Network

Presented by;Steve HolmesApplication EngineerTektronix

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Testing to Measurement Guidelines

When you test something you need to have a Standard orGuideline to test to.

– The best known Test guideline is known as ETSI TR 101 290. DigitalVideo Broadcasting (DVB); Measurement guidelines for DVB systems,or AKA TR101-290

– The ATSC has also recently introduced ATSC Recommended Practice:Transport Stream Verification A78

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Testing to Measurement Guidelines

TR101-290 Tests are broken into 3 Priorities– First priority: Sync, PAT & PMT, Continuity …..

– Decoder lock

– Second priority: PCR’s, CRC’s, RF FEC– Program Decode

– Third priority: EPG– PSIP

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Testing to Measurement Guidelines

ATSC A78 Transport Stream Verification– ATSC Error Characterization

– Transport Stream Off Air (TOA)– The station is effectively off-air

– Program Off Air (POA)– A main service (virtual channel) is flawed

– Component Missing (CM)– One of the program components that is signaled by PSIP or the PMT

– Quality Of Service (QOS)– Parameters are out of specification by such a margin

– Technically Non-Conformant (TNC)– Violates the letter of the standard

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MPEG Tables

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TR101-290 & ATSC test Recommendations

Baseband measurements split into 3 groups– 1st priority

– Required for Decode ability

– Basic Monitoring

– 2nd priority– Recommended monitoring

– Program Decodeability

– 3rd priority– Application Dependant – PSIP

– May cause a decoder from finding a service

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TR101-290 & ATSC test Recommendations

– ATSC Error Characterization is in 5 groups– Transport Stream Off Air (TOA)

– Program Off Air (POA)

– Component Missing (CM)

– Quality Of Service (QOS)

– Technically Non-Conformant (TNC)

One of the Issues with A78 is that No stream is100% Technically Conformant

The second is that when you get an error you mayget several alarm lights for the same alarm

(more later)

Tektronix does both TR101-290And

ATSC A78

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TR101-290 & ATSC test Recommendations

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Alarms for Trouble shooting

We will be looking at TR101-290 for most of this.

TR101-290 does a better job of trouble shooting analysis.

ATSC A78 does a better job of Categorizing monitoring issues.

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TR101-290 1st Priority

No: Indicator

1.1 * TS_sync_loss1.2 * Sync_byte_error1.3 + PAT_error1.4 * Continuity_count_error1.5 + PMT_error1.6 + PID_error

* Transmission Monitoring

+ Encoder Monitoring

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TR101-290 2nd Priority

No: Indicator

2.1 # Transport_error2.2 * CRC_error2.3 * + PCR_error2.4 * + PCR_accuracy_error2.5 + PTS_error2.6 + CAT_error

* Transmission Monitoring

+ Encoder Monitoring# RF FEC overflow Monitoring

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TR101- 290 3rd Priority – DVB / ATSC

PSIP_Error

MGT_Rate

STT_Rate

RRT_Rate

EIT_Rate

VCT_Rate

EPG Data inserterMonitoring

Indicator

DVB ATSC

NIT_error

SI_repetition_error

Unreferenced_PID

SDT_error

EIT_error

TDT_error

RST_error

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Keys to MPEG Monitoring FlexVu

MPEG Monitoring using FlexVu (Your Viewof your Transport stream)

Thumbnails

Three Programs

TR 101 290

Level/Priority 1, 2, 3

ATSC

Current Errors

Past errors

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Program Centric Monitoring View

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Test Centric Monitoring View

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Key Monitoring and Test challenges

What makes the phone ring– Loss of signal– Loss of a program– Picture breaking up– Audio breakup

– Not a PMT being 20ms over the limit

When monitoring MPEG it’s some what like monitoring Video, everythingis not Black & White.

– We do not reject video that is at 101IRE instead of 100IRE. The same goesfor MPEG monitoring some things can be tolerated and some can not. TheKey is to know the difference and what can show up in the picture.

MPEG monitoring falls into two categories.– Things that are Binary (Good/Bad)– Things that have acceptable working windows of operation

Looking at the network only does not catch the errors– Your customers that are watching Video that comes from the MPEG stream

are not looking at the network. You have to Monitor the MPEG layer as wellas the Network Layer.

The key is knowing who does what and how far can it go.

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Key Monitoring and Test challenges

Binary alarms– Are things that must be in the

stream for proper operation.Things like;

– The sync byte

– Sync byte error

– Continuity counter

– Transport Error Flag

– Any MPEG2 table missing formore than 1 second

If any of these are missing orincorrect the Transport Streamwill have major errors

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Key Monitoring and Test challenges

Adjustable alarms– Are things like how often a particular table arrives. The timing swing of

the PCR.– PAT timing MPEG2/ ATSC Limits 100 ms or less

– up to 500 ms should not cause a program issue*

– PMT timing MPEG2/ ATSC Limits 400 ms or less– up to 2000 ms should not cause a program issue*

– PCR timing MPEG2/ ATSC Limits 100 ms or less– up to 500 ms should not cause a program issue*

– PTS timing MPEG2/ ATSC Limits 700 ms or less– up to 3500 ms should not cause a program issue*

PCR Jitter Frequency errors– PCR inaccuracy MPEG2/ATSC Limits +/– 500 ns or less

– up to +/- 2500 ns should not cause a program issue* **

– PCR overall jitter MPEG2/ATSC Limits +/-25 μs or less– up to +/-125 μs should not cause a program issue*

* Per ATSC A78/SCTE 134 Recommended Practice:Transport Stream Verification

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Network Monitoring Points

Source

En

co

der

Mu

x

8V

SB

Mo

dNetworkSTL

Analog or SDIAnalog or SDI(WFM7120), and(WFM7120), andPicture QualityPicture Quality

MonitoringMonitoringTest PointTest Point

Protocol AnalysisProtocol Analysisof MPEGof MPEG--2 Transport Stream2 Transport Stream

and associated DVB or ATSC tablesand associated DVB or ATSC tablesMTM400MTM400

8V

SB

PA

8VSB RF8VSB RFTransmissionTransmission

TestingTesting

MT

M400

MT

M400

MT

M400

MT

M400

MT

M400

MT

M400

Monitoring heregives you a endto end view ofyour network

Monitoring heregives you a lookat the input to

the STL

Monitoring heregives you a atthe output ofthe STL or theRF power tap

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Network Monitoring Via RF MTM400

Source

En

co

der

Mu

x

8V

SB

Mo

dNetworkSTL

Analog or SDIAnalog or SDI(WFM7120), and(WFM7120), andPicture QualityPicture Quality

MonitoringMonitoringTest PointTest Point

8V

SB

PA

MT

M400

MT

M400

PSIP

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Station #1

No Transport stream ErrorsNo errors on the ProgramsHas CaptionsNo Program Ratings in the EIT.

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Station #1

No Channel Data showing upNo Channel Data showing up

Packets being sent but no Current Channel dataPackets being sent but no Current Channel data

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Station #2

No Transport Stream ErrorsNo PSIP ErrorsHas CaptionsHas EPG Program Ratings

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Station #3

Minor Video Alarm

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Station #3

Primary Error is the RRT MissingExtra data in Transport streamformatted incorrectlyMinor PCR Frequency Offset

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Station #4

No Major Transport Stream ErrorsVideo Good Captions & Ratings

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Station #4

EIT Sub Table Repetition slightly over the Limit

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Station #5

Several Transport Stream RF hits while RecordingNo EPG Program RatingsHas Captions

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Station #5

MER is at 19.3 most others at 29+

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Good RF Symbol

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Station #6

Some Transport Stream errors (no Video Errors)Missing RRTHas CaptionsHas Program Rating in EPG

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KTTV

EIT just over limitRF looks good

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ATSC A78 Network Monitoring Via RF MTM400

Source

En

co

der

Mu

x

8V

SB

Mo

dNetworkSTL

Analog or SDIAnalog or SDI(WFM7120), and(WFM7120), andPicture QualityPicture Quality

MonitoringMonitoringTest PointTest Point

8V

SB

PA

MT

M400

MT

M400

PSIP

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8VSB

Modulation

8VSB RF Receiver Measurements

ATSC MPEG Tables (TVCT, CVCT)

MPEG Transmission alarm parameters (ETSI TR101-290)

Constellations– Does 8VSB have constellation to look at?

– If so what do they look like? (Good ones –Bad ones)

RF measurement– Does 8VSB have a MER reading, if so what’s a good reading?

– What are the Power levels?

– TFE’s what are they, do I care?

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8VSB

Constellations

8VSB Constellation at 27dB MER

-4dBmv0.0 Pre RS BER

No Errors, No TEF’s

10db of MER headroom28db of RF headroom

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8VSB

Constellations

8VSB Constellation at 22dB MER

-4dBmv2.2E-6 BER pre RSNo Errors, No TEF’s

Channel change from 27 dB MER

(5 dB of MER Headroom)

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8VSB

Constellations

8VSB Constellation at 17dB MER

-31dBmv8.9E-4 BER pre RSNo Errors, No TEF’s

Any more drop in signal or MER andErrors were passed to the Screen.

(28dB of padding)Don’t confuse RF levels and MER

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Summary

TR101-290 is the MPEG testing standard with tests that are broken into 3Priorities

– Program Analysis– PCR Analysis– Bandwidth

– PSIP Analysis

The MPEG Transport Stream monitors– Compliance to MPEG-2 standard

– support for DVB and ATSC tables.

– Simple identification of errors– Detailed analysis of problem

– Protocol and syntax– Continuity Counter– Data Rates of Transport– PCR analysis

Key attributes are:– Wide range of network interfaces– Flexibility in setting thresholds & alarms to predict network performance– Real time operating system to match the up time of your network

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MPEG Transport Stream Monitoring

Summary

Compliance to MPEG-2standard

– Display DVB and ATSC tables

Simple identification of errors– “What makes the phone ring?”

Detailed analysis of problem– Protocol and syntax

– Continuity Counter

– Data Rates of Transport

– PCR analysis

IP traffic measurements– Correlate dropping IP packets

to MPEG timing problems andvideo quality

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