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Aspect Ratio and Active Format Description Gerry Field American Public Television

Aspect Ratio and Active Format Description Gerry Field American Public Television. Aspect Ratio. Television Aspect Ratio Defined: Picture frame: Ratio of image width to image height. Not directly tied to resolution Historically, TV content and frame had been 4:3

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Aspect Ratio and Active Format Description Gerry Field American Public Television

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  1. Aspect Ratioand Active Format DescriptionGerry FieldAmerican Public Television WGBH Public Television Quality Workshop

  2. Aspect Ratio Television Aspect Ratio Defined: Picture frame: Ratio of image width to image height. Not directly tied to resolution Historically, TV content and frame had been 4:3 Content is both 4:3 and 16:9. 16:9, 4:3, 15:9, 14:9, 1.85:1, 2.39:1, mixed aspect ratio TV frame is now 16:9 in > 50% households Millions of 4:3 receivers remain in use Channels are both 16:9 and 4:3 WGBH Public Television Quality Workshop 2

  3. Source Program Channel Viewer It’s Simple WGBH Public Television Quality Workshop

  4. 4:3 Image - 4:3 Frame 4:3 Image - 16:9 Frame 16:9 Image - 16:9 Frame 16:9 Image - 4:3 Frame WGBH Public Television Quality Workshop 4

  5. What Happens Downstream? 4:3 Channel Letterboxed 16:9 Typical for Multicast or Cable 16:9 Home Display Adds Pillars Results in “Breadbox” WGBH Public Television Quality Workshop 5

  6. What Happens Downstream?Center Cut Alternative 16:9 Frame Center Cut 4:3 One Alternative 4:3 Channel Center Cut 4:3 Typical for Multicast or Cable 16:9 Home Display Adds Pillars No “Breadbox” WGBH Public Television Quality Workshop 6

  7. However…It Doesn’t Work For All Content 16:9 Frame Center Cut 4:3 NOT Center Cut Safe 4:3 Channel Center Cut 4:3 NOT Center Cut Safe 16:9 Home Display Center Cut 4:3 NOT Center Cut Safe WGBH Public Television Quality Workshop

  8. Worst CaseThis Never Happens, Right?… Letterboxed to 4:3 “Postage Stamp” To a 16:9 Home Display 4:3 Frame Letterboxed Content Downconverted for 4:3 Using Letterbox Upconverted to 16:9 Typical Primary Channel WGBH Public Television Quality Workshop

  9. Anamorphic Only Use as a Distribution Technique Not as a Broadcast Format Most common is SD widescreen on D-Beta Must be properly “stretched” prior to emission If not, viewer sees “squashed” picture Common practice is to upconvert to HD at a bitrate cost WGBH Public Television Quality Workshop

  10. Speaking of SD & Widescreen 16:9 is not limited to HD 16:9 SD is included in ATSC A/53 standard. and is regularly used in domestic and overseas markets 16:9 SD can be distributed if MPEG2 encoder flag is set to 16:9. SD 16:9 can co-exist with SD 4:3 WGBH Public Television Quality Workshop

  11. Distributing SD Widescreen Current workflow would need to be modified Testing and vendor support required Business requirements need to match 16:9 HD or 16:9 SD Sencore IRD MRD3187 4:3 SD Center Cut Source SD 16:9 File or Anamorphic Tape 4:3 SD, 16:9 Letterbox WGBH Public Television Quality Workshop

  12. Active Format Description AFD A four bit code to define the active and protected image area. Intended to guide professional video equipment, consumer receivers and set-top boxes to optimize the displayed image. Very few ATSC receivers and consumer decoders act on AFD. WGBH Public Television Quality Workshop

  13. May also be used for format conversion signaling in the post and pre-broadcast chain. References: - SMPTE ST 2016-1:2009 - PBS TOS-1, 4.4 - PBS TOS-21, 4.3.7 - PBS Connect > Engineering/Compute > Technical Reference Library Active Format Description AFD WGBH Public Television Quality Workshop

  14. AFD Codes SMPTE ST 2016-1:2009 defines 17 AFD Codes. Four are in common use: 1000 – Full Frame 1001 – Full 4:3 / Pillarbox 1010 – Protected 16:9 1111 – Center Cuts (14:9, 15:9, 2.35 etc. treated as 16:9) WGBH Public Television Quality Workshop

  15. AFD = ‘1000’ (Full Frame) In a 4:3 coded frame In a 16:9 coded frame WGBH Public Television Quality Workshop 15

  16. AFD = ‘1001’ (Full 4:3 / Pillarbox) In a 4:3 coded frame In a 16:9 coded frame In a 4:3 coded frame, AFD code ‘1001’ represents the same image display as AFD code ‘1000’. AFD code ‘1000’ is the preferred coding for a full frame 4:3 image WGBH Public Television Quality Workshop 16

  17. AFD = ‘1010’ (Protected 16:9) In a 4:3 coded frame In a 16:9 coded frame WGBH Public Television Quality Workshop 17

  18. AFD = ‘1111’ (Center Cuts) In a 4:3 coded frame In a 16:9 coded frame WGBH Public Television Quality Workshop 18

  19. Consumer Issues WGBH Public Television Quality Workshop

  20. Consumer Issues Broadcasters cannot rely on consumers to maintain aspect. AFD is not widely implemented on consumer devices. WGBH Public Television Quality Workshop

  21. So What do we do? Educate. Implement AFD. Discuss with Cable and Satellite providers to Implement AFD on their SD Down convert. Produce when appropriate 16X9 Center cut safe material. If necessary up convert Letterbox to 16X9 Full frame. Consider SD Widescreen distribution & channels WGBH Public Television Quality Workshop

  22. Aspect Ratioand Active Format DescriptionGerry FieldAmerican Public Television WGBH Public Television Quality Workshop 22

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