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HDTV INTEROPERABILITY

HDTV INTEROPERABILITY. Philip Laven Director, Technical Department European Broadcasting Union Brussels 21 January 2005. SOME JARGON. Scanning formats for SDTV 625-line TV has 576 active horizontal lines 525-line TV has 480 active horizontal lines Two image formats for HDTV

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HDTV INTEROPERABILITY

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  1. HDTV INTEROPERABILITY Philip Laven Director, Technical Department European Broadcasting Union Brussels 21 January 2005

  2. SOME JARGON . . . . • Scanning formats for SDTV • 625-line TV has 576 active horizontal lines • 525-line TV has 480 active horizontal lines • Two image formats for HDTV • 1080 active horizontal lines • 720 active horizontal lines • Choices: 1080i, 720p or 1080p • Interlaced or progressive scanning?

  3. INTERLACED SCANNING

  4. PROGRESSIVE SCANNING

  5. INTERLACED v. PROGRESSIVE • Interlaced scanning is an old (but effective) technique for bandwidth reduction • Modern compression techniques offer better performance than the fixed interlacing technique • ALL compression schemes deliver better results at lower bit rates with progressive sources • As modern HDTV displays are inherently progressive, progressive scanning is the logical choice for emission • If sources and displays are both progressive, use of interlace should be avoided in the signal path

  6. SCANNING FORMATS • Format “wars” in the USA resulted in the ATSC standard including 18 scanning formats • IBC 2004 saw renewed debates about formats • 1080p/50 is ideal, but not practical today • Until 1080p/50 becomes viable, broadcasters must choose between 1080i/25 and 720p/50 • Which format is “best”? 1280 1920 0.92 million pixels 2.07 million pixels 720 1080

  7. PIXEL COUNTING • Although 1080i seems to offer more than double the number of pixels, we must avoid comparing “apples” and “oranges” • If you look carefully at interlaced pictures, you will see “inter-line twitter” which reduces the subjective vertical resolution • In subjective terms, 1080i and 720p deliver the SAME vertical resolution

  8. STATIC RESOLUTION • 1080 x 1920 systems potentially give greater horizontal resolution than 720 x 1280 systems • 1280/1920 = 66.7% of horizontal resolution • In practice, 95% of current 1080i cameras have 1440 pixels horizontally (rather than 1920 pixels) • 1280/1440 = 88.9% of horizontal resolution • Similarly, few displays can today reproduce the full horizontal resolution of 1920 pixels • In summary: 1080i has the same vertical resolution as 720p 1080i has slightly better horizontal resolution

  9. MOTION PORTRAYAL • Static resolution is important for still pictures, but very few TV pictures are “static” • e.g. most sports coverage involves rapid movement and unpredictable camera zooming • Progressive scanning gives improved motion portrayal – especially for slow-motion • The choice between 1080i and 720p is a balance between static resolution and motion portrayal • 1080i offers better static resolution • 720p offers better motion portrayal • Which is more important to you?

  10. INTERLACED v. PROGRESSIVE

  11. Difficult conversion Interlaced Progressive Easy conversion

  12. INTERESTING ADVICE • Following my presentation at IBC in September, one member of the audience said: • “I am amazed that anybody would consider launching new services based on interlace” • “I have spent all of my life working on conversion from interlace to progressive” • “Now that I have sold my successful company, I can tell you the truth: interlace to progressive does not work!” • When asked to give his name, he replied: • Yves Faroudja = the world’s foremost expert on format converters

  13. 2nd GENERATION HDTV • DVB Stand at IBC 2004 showed: • first live demonstration of DVB-S2 satellite transmissions • two 720/50p services (BSkyB & BBC) • coded at 7.5 Mbit/s using different video compression schemes • MPEG-4 AVC & Microsoft VC1 • software decoding • European broadcasters are very interested in launching HDTV services based on a combination of new technologies → second generation HDTV

  14. EBU POSITION ON HDTV • EMISSION standards for HDTV should be based on progressive scanning: • 720p/50 is currently the optimum solution, but 1080p/50 is an attractive option in the longer term • Although there are strong technical arguments in favour of progressive scanning for emission, the EBU recognises that some broadcasters might wish to broadcast 1080i programme material

  15. EBU POSITION ON HDTV (continued) • As consumer electronics equipment (e.g. set-top boxes and displays) will accept both 720p/50 and 1080i/25 formats, broadcasters will be able to select either of these formats – even on a programme-by-programme basis • HDTV PRODUCTION equipment should support: • 720p/50 • 1080i/25 • 1080p/25 • 1080p/50 in the longer term

  16. 1080p/50 • 1080p/50 represents 3rd generation HDTV • It has an uncompressed data rate of ~ 3 Gbit/s • studio interfaces must be defined • do we need lossless compression in the studio? • what about interfaces between the set-top box and display? • more advanced compression systems? • Despite such challenges, 1080p/50 is an attractive production format for high-quality production • easy to derive 1080i/25 and 720p/50 versions • offers future-proofing of valuable content

  17. AVOIDING FORMAT WARS • Commercial and political pressures have long influenced the selection of TV standards • In setting HDTV standards, we should avoid “half-truths” about technical matters • The EBU plans to undertake subjective tests that will test many of the assertions made by the advocates of the competing standards • The EBU wants broadcasters to be able to make “educated choices”

  18. SCIENTIFIC TESTING . . . . Source Conversion Transmission Display 1080p 1080 1080i 1080p Compression 768 720p 720 Other

  19. INTEROPERABILITY ISSUES • The emergence of two emission formats for HDTV in Europe (720p/50 and 1080i/25) is NOT a problem because HDTV set-top boxes and displays will accept both formats • The availability of two video compression schemes (e.g. MPEG-4 AVC and Microsoft VC-1) may cause some interoperability issues • Will set-top boxes work on both schemes? • The introduction of 1080p/50 will not be compatible with set-top boxes or displays • Long term issue . . . . .

  20. INTEROPERABILITY ISSUES • Many HDTV displays now on sale in Europe do not support the HDMI interface and will not operate with HDMI-equipped set-top boxes • urgent need for HD-ready label for displays • HDTV set-top boxes for pay-TV services will probably have proprietary conditional access systems and proprietary APIs • potential interoperability problem • will pay-TV set-top boxes be able to receive free-to-air HDTV services? • need for HD-ready labels for set-top boxes

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