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

Aspect Ratioand

Active Format Description

How do we make it all fit?

San Francisco Public Television Quality Workshop

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.

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.

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.

4:3 Image in a 4:3 Display

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.

4:3 Image in a 16:9 Frame

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.

16:9 Image “Letterboxed” in 4:3 Frame

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.

16:9 Image

16:9 Center Cut in 4:3 Frame

However…..

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

16:9 Image Center cut Artifacting

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”.

Up Converted to 16:9 as 4:3

Down converted 4:3 Letterbox

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.

Full Screen 16:9

Anamorphic 4:3

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

Unacceptable method of distributing HD material.

Unacceptable as a distribution format.

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.

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 2nd and 3rd SD sets.

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.

Active Format Description - AFD

May also be used for format conversion signaling in the post and pre-broadcast chain.

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.

1000 – Full Frame into 16:9 Letterbox

As the coded frame

Letter-box 16:9 into 4:3scan

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

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

1010 – 16:9 Into 4:3 Protected Letterbox

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

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

16:9(with shoot & protect 4:3 centre)

Centre cut-out 4:3 from16:9

Consumer Issues

Consumer Issues Broadcasters cannot rely on consumers to

maintain aspect.

AFD is not widely implemented on consumer devices.

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.

Questions? / Comments

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

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