Over-the-Air (OTA) Bit Management David Felland Milwaukee Public Television.

Over-the-Air (OTA) Bit Management

David FellandMilwaukee Public Television

Acquisition and Distribution New impacts on broadcast transport stream

Better coding efficiency in new HD encoders○ Claims of 10-15% improvement○ Potential for two 720p HD services in one

transport stream – or other servicesMore SD services from which to chooseMobile DTVFixed and Mobile DTV Data Services

Public television has used its spectrum to serve diverse audiences with more variety in content (“multicasting”)Pluses: greater range of services; potential higher

value to individual communitiesMinuses: locked into audience expectations;

stations are forced to balance video quality with service quantity

Tradeoffs affect Quality:

Bit Management Some options for broadcasters

Reduced horizontal resolution (1440 vs 1920)Noise reduction of both HD and SDModern statistical multiplexing720p vs. 1080i

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What are stations doing? Surveyed the ETAC

1-3 OTA servicesDifferent services plans among all membersFocus on HD + national / local SD services

HD SD1 SD2 SD3 SD4 PSIP Data

#1 15 3 - - - 150k 128k

#2 12 2.5 2.5 - - 250k 1M+

128k

#3a 12 3 1.5 - - 565k 128k

#3b - 4 2 - - 256k 100k

ETAC Members’ OTA

Italics = Stat Mux Pool


#4 16 2 - - - 300k 128k+

100k

#5a 18 - - - - ~200k 128k

#5b - 4 3.5 0.7 0.7 242k 128k

#6 14 - - - - 200k 1M

ETAC Members’ OTA

(x4) (x2) (x2)



#7 11 2 2 2 - 250k -

#8 11.5 4 4 0.3 - 250k 250k+

128k

#9 - 3 3 3 3 150k 6M

#10 11 1.5 3.5 - - 2M -

ETAC Members’ OTA



#11a 12.5 3.4 3.4 - - 150k 128k+110k

#11b - 3.4 3.4 3.4 3.4 150k 128k+

110k

#11c 12.5 3.4 3.4 - - 150k 128k+110k

#12 12 2.1 2.1 - - 200k -

ETAC Members’ OTA

(x2)



#13 11 6 - - - 180k 128k

#14 10 3 3 - - 150k 1M+

300k

ETAC Members’ OTA


Mobile DTV Bandwidth UsageHow much OTA spectrum is needed?

Mobile / Handheld service requirementsMultiple modes – e.g., “Half-rate”,

“Quarter-rate”, or a variety of “Mixed Modes”

Many broadcasters will use Quarter or Mixed○Quarter ~17% payload (83% FEC)○Mixed (e.g., ½, ¼, ¼, ¼) ~ 26% (74% FEC)○Half ~34% payload (66% FEC)

Bandwidth Usage (bits)How much OTA spectrum is needed?

Mixed Mode examples (26%):One 500 kbps stream ~1.92 Mbps

○Video@400kbps; Audio@64kbps; Data@30kbpsTwo 500 kbps streams ~3.85 Mbps

Quarter Rate examples (17%):One 500 kbps stream ~2.94 Mbps

○Video@400kbps; Audio@64kbps; Data@30kbpsTwo 500 kbps streams ~5.88 Mbps

Some Mobile PTV Services Simulcast of Local HD or SD Services Simulcast of National HD or SD Services Stand alone Local Mobile Services National or Local Kids Service “Radio” Services

Audio Only – 16 – 48 kbps“Audio with Pictures” – same as Video/Audio

DTV Spectrum Usage:ETAC Member #1

~15 Mbps

~3 Mbps

150 kbps128 kbps

• HD program

• PSIP• SD program

• Data/Ancillary

19

.4 M

b/s

DT

V T

ran

sp

ort

S

tre

am

Sta

t M

ux

Po

ol


~12 Mbps

~2.5 Mbps250 kbps

1Mbps+128 kbps

• HD program

• PSIP

• SD program

• Data/Ancillary

~2.5 Mbps • SD program

19

.4 M

b/s

DT

V T

ran

sp

ort

S

tre

am

Sta

t M

ux

Po

ol

ETAC Member #1:One Mobile Service (Mixed)

~13.5 Mbps

19

.4 M

b/s

DT

V T

ran

sp

ort

S

tre

am

~2.5 Mbps

150 kbps128 kbps

• HD program


• Data/Ancillary~2 Mbps • Mobile program

Sta

t M

ux

Po

ol

ETAC Member #2:One Mobile Service (Mixed)

~11 Mbps

~2 Mbps250 kbps

1Mbps+128 kbps

• HD program


• Data/Ancillary

~2 Mbps • SD program

19

.4 M

b/s

DT

V T

ran

sp

ort

S

tre

am

Sta

t M

ux

Po

ol

~2 Mbps • Mobile program


~10 Mbps

~3 Mbps

150 kbps

1Mbps

• HD program


• Data/Ancillary

~3 Mbps • SD program

19

.4 M

b/s

DT

V T

ran

sp

ort

S

tre

am

Sta

t M

ux

Po

ol

ETAC Member #14:Multiple Mobile Services (Mixed)

~9.5 Mbps

~1.8 Mbps250 kbps1Mbps

• HD program


• Data/Ancillary

~1.8 Mbps • SD program

19

.4 M

b/s

DT

V T

ran

sp

ort

S

tre

am

Sta

t M

ux

Po

ol

~2 Mbps • Mobile program~2 Mbps • Mobile program

• Radio Services (100k)

Other Stations:Possible Mobile Services (Mixed)

~11 Mbps

250 kbps

• HD program

• PSIP

19

.4 M

b/s

DT

V T

ran

sp

ort

S

tre

am

Sta

t M

ux

P

oo

l~2 Mbps • Mobile program~2 Mbps • Mobile program~2 Mbps

~2 Mbps • Weather

• Mobile program

Other Stations:Possible Mobile Services (1/4 rate)

~11 Mbps

250 kbps

• HD program

• PSIP

19

.4 M

b/s

DT

V T

ran

sp

ort

S

tre

am

Sta

t M

ux

P

oo

l~3 Mbps • Mobile program

~3 Mbps • Mobile program

~2 Mbps • Weather

Other Stations:Possible Mobile Services (Mixed)

~4.5 Mbps

100 kbps

• SD program

• PSIP

19

.4 M

b/s

DT

V T

ran

sp

ort

S

tre

am

~2 Mbps • Mobile program• Mobile program• Mobile program

~2 Mbps~2 Mbps~2 Mbps~2 Mbps~2 Mbps~2 Mbps

• Mobile program• Mobile program• Mobile program• Mobile program

Sorry but No Free Lunch! MPEG very cleverly hides picture errors BUT

Errors hidden at one stage can appear downstream Don’t use an extra codec cycle simply because you can

Use suitable workflow techniquesDon’t over compress master recordingsPlot your program performance to the end userTest and understand how to use MPEG tools properly

How does my show look? Examples of original video compared to:

720 progressive at different station presentation rates1080 interlace at different station presentation rates

Producer tech choices drive the viewer experienceDownstream network workflow and distributionLocal station bandwidth constraints and practices Quality pictures at home require Best Practices

upstream

Some Best Practices Use progressive acquisition cameras

Use higher frame rates Avoid interlace – Digital TV handles it inefficiently

Streamline post production workflowSuccessive coders will reduce picture qualityAssume your show will look worse downstream Prove that the tools you use “do minimal harm”

Observations and Suggestions: Many stations are moving to 720p replacing spatial

resolution with improved temporal resolutionSignificantly reducing picture blocking artifactsReducing horizontal resolution

With an increase in demand for more services public television can improve performance byDropping interlace and moving to progressive picturesReplacing older HD encoders with the next generationChanging PBS satellite distribution to progressive

QG

Video Examples

QG

Questions?

Over-the-Air (OTA) Bit Management David Felland Milwaukee Public Television.

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