16:9 (center)

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Aspect Ratio and Active Format Description How do we make it all fit?

San Francisco Public Television Quality Workshop

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Aspect Ratio  Television Aspect Ratio Defined: Ratio of the width of an image to its height.  HD Screens are 16:9.

 SD Screens are 4:3.

 Programming is ????.

 16:9, 4:3, 15:9, 14:9, 1.85:1, 2.39:1 etc.

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How do we make it all fit?

 We must deal with two display sizes 16:9 and 4:3.

 16:9 Sets have over 50% household Penetration.

 Number of TV sets in the average U.S. household: 2.86.  Percentage of U.S. homes with three or more TV sets: 54.

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How do we make it all fit?

 There are two programming sizes 16:9 and 4:3.

 Treat all widescreen as 16:9 unless we wish to side crop other formats such as 15:9, 14:9, 1.85:1 2.39:1 etc.

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4:3 Image in a 4:3 Display 5

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16:9 Image in a 16:9 Display 6

But…How do we make it all fit?

 4:3 SD up converted to HD Fills the height of the 16:9 frame but leaves blank “pillar boxes” on the sides.

 Not a real problem if original quality is high.

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4:3 Image in a 16:9 Frame 8

But…How do we make it all fit?

 16:9 HD Down Converted to 4:3 Fills the width of a 4:3 frame but leaves blank spaces on Top and Bottom.

 “Letterboxed” Not perfect for 4:3 but may be acceptable.

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16:9 Image “Letterboxed” in 4:3 Frame

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But…How do we make it all fit?

 16:9 HD can also be “Center Cut” Down Converted to 4:3. This fills the height and width of a 4:3 frame but omits material on the left and right of the original image.

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16:9 Image 12

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16:9 Center Cut in 4:3 Frame 13

However…..

 Center Cut is only feasible if all active elements and graphics are maintained in the 4:3 center of the 16:9 image.

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16:9 Image in a 16:9 Display 15

16:9 Image Center cut Artifacting

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Worst Case  Letterbox up converted to 16:9 as a 4:3.

 Then down converted using a 16:9 to 4:3 down converter.

 “Postage Stamp”.

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16:9 Image in a 4:3 Display 18

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Up Converted to 16:9 as 4:3 19

Down converted 4:3 Letterbox

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What is the proper way to do this?

 There is no incorrect method.

 Commercial Networks Up Convert 4:3 with side panels. Down Convert 16:9 by Center Cut.  PBS Stations Up Convert primarily 4:3 with side panels and Down Convert by Center Cutting or Letterboxing.

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Full Screen 16:9 22

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Anamorphic 4:3 23

Anamorphic  Full 16:9 “squashed” into a 4:3 frame.

 Unacceptable method of distributing HD material.

 Unacceptable as a distribution format.

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Anamorphic  Anamorphic programming must be up converted to 16:9 HD then distributed.

 Distributor up converts once as opposed to stations each having to deal with an additional format.

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Down Converting  We don’t have to, ATSC is 16X9 HD !

 Some stations are still SD only.

 50 % of our viewers are still SD.

 Most HD households still have 2 nd sets.

and 3 rd SD

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Active Format Description - AFD  A four bit code to define the active and protected image area.

 Intended to guide receivers and set-top boxes to optimize the displayed image.

 Very few ATSC receivers and consumer decoders act on AFD.

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Active Format Description - AFD  May also be used for format conversion signaling in the post and pre-broadcast chain.

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AFD Codes  There are 16 AFD Codes.

 Realistically only four will be used.

    1000 – Full Frame into 16:9 Letterbox.

1001 – 16:9 Center Cut into 4:3 Pillarbox.

1010 – 16:9 Into 4:3 Protected Letterbox 1111 –16:9 image with alternate 4:3 center  14:9, 15:9, 2.35 etc. treat as 16:9.

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1000 – Full Frame into 16:9 Letterbox

Letter-box 16:9 into 4:3 scan As the coded frame

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1001 – 16:9 Center Cut into 4:3 Pillar-box

Center cut-out 4:3 from 16:9 4:3 (center)

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1010 – 16:9 Into 4:3 Protected Letterbox

Letter-box 16:9 into 4:3 scan 16:9 (center)

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1111 –16:9 image with alternate 4:3 center

16:9 (with shoot & protect 4:3 centre) Centre cut-out 4:3 from 16:9 QG

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Consumer Issues 34

Consumer Issues  Broadcasters cannot rely on consumers to maintain aspect.

 AFD is not widely implemented on consumer devices.

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So What do we do?

 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.

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Questions? / Comments 37

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