Over-the-Air (OTA) Bit Management David Felland Milwaukee 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 services More SD services from which to choose Mobile DTV Fixed 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 communities Minuses: 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 SD Modern statistical multiplexing 720p vs. 1080i ☺ X X ☺

What are stations doing?  Surveyed the ETAC 1-3 OTA services Different services plans among all members Focus on HD + national / local SD services

HDSD1SD2SD3SD4 PSIPData # k128k # k1M+ 128k #3a k128k #3b k100k ETAC Members’ OTA Italics = Stat Mux Pool

HDSD1SD2SD3SD4 PSIPData # k128k+ 100k #5a ~200k128k #5b k128k # k1M ETAC Members’ OTA (x4) (x2) Italics = Stat Mux Pool

HDSD1SD2SD3SD4 PSIPData # k- # k250k+ 128k # k6M # M- ETAC Members’ OTA Italics = Stat Mux Pool

HDSD1SD2SD3SD4 PSIPData #11a k 128k+ 110k #11b k 128k+ 110k #11c k 128k+ 110k # k- ETAC Members’ OTA (x2) Italics = Stat Mux Pool

HDSD1SD2SD3SD4 PSIPData # k128k # k1M+ 300k ETAC Members’ OTA Italics = Stat Mux Pool

Mobile DTV Bandwidth Usage How much OTA spectrum is needed?  Mobile / Handheld service requirements Multiple 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 ○ Two 500 kbps streams  ~3.85 Mbps  Quarter Rate examples (17%): One 500 kbps stream  ~2.94 Mbps ○ Two 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 kbps 128 kbps HD program PSIP SD program Data/Ancillary 19.4 Mb/s DTV Transport Stream Stat Mux Pool

DTV Spectrum Usage: ETAC Member #2 ~12 Mbps ~2.5 Mbps 250 kbps 1Mbps+128 kbps HD program PSIP SD program Data/Ancillary ~2.5 Mbps SD program 19.4 Mb/s DTV Transport Stream Stat Mux Pool

ETAC Member #1: One Mobile Service (Mixed) ~13.5 Mbps 19.4 Mb/s DTV Transport Stream ~2.5 Mbps 150 kbps 128 kbps HD program PSIP SD program Data/Ancillary ~2 Mbps Mobile program Stat Mux Pool

ETAC Member #2: One Mobile Service (Mixed) ~11 Mbps ~2 Mbps 250 kbps 1Mbps+128 kbps HD program PSIP SD program Data/Ancillary ~2 Mbps SD program 19.4 Mb/s DTV Transport Stream Stat Mux Pool ~2 Mbps Mobile program

DTV Spectrum Usage: ETAC Member #14 ~10 Mbps ~3 Mbps 150 kbps 1Mbps HD program PSIP SD program Data/Ancillary ~3 Mbps SD program 19.4 Mb/s DTV Transport Stream Stat Mux Pool

ETAC Member #14: Multiple Mobile Services (Mixed) ~9.5 Mbps ~1.8 Mbps 250 kbps 1Mbps HD program PSIP SD program Data/Ancillary ~1.8 Mbps SD program 19.4 Mb/s DTV Transport Stream Stat Mux Pool ~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 Mb/s DTV Transport Stream Stat Mux Pool ~2 Mbps Mobile program ~2 Mbps Mobile program ~2 Mbps Weather Mobile program

Other Stations: Possible Mobile Services (1/4 rate) ~11 Mbps 250 kbps HD program PSIP 19.4 Mb/s DTV Transport Stream Stat Mux Pool ~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 Mb/s DTV Transport Stream ~2 Mbps Mobile program ~2 Mbps 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 techniques Don’t over compress master recordings Plot your program performance to the end user Test 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 rates 1080 interlace at different station presentation rates  Producer tech choices drive the viewer experience Downstream network workflow and distribution Local 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 workflow Successive coders will reduce picture quality Assume 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 resolution Significantly reducing picture blocking artifacts Reducing horizontal resolution  With an increase in demand for more services public television can improve performance by Dropping interlace and moving to progressive pictures Replacing older HD encoders with the next generation Changing PBS satellite distribution to progressive

Q G Video Examples

Q G Questions?