Aspect ratio and active format description how do we make it all fit
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Aspect Ratio and 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 ????.

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Aspect ratio and active format description how do we make it all fit
Aspect RatioandActive Format DescriptionHow do we make it all fit?

San Francisco Public Television Quality Workshop


Aspect ratio
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.


How do we make it all fit
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.


How do we make it all fit1
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.




But how do we make it all fit
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.



But how do we make it all fit1
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.



But how do we make it all fit2
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.




However
However…..

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




Worst case
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”.





What is the proper way to do this
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.




Anamorphic
Anamorphic

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

Unacceptable method of distributing HD material.

Unacceptable as a distribution format.


Anamorphic1
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
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
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 afd1
Active Format Description - AFD

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


Afd codes
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
1000 – Full Frame into 16:9 Letterbox

Letter-box 16:9 into 4:3

scan

As the coded frame


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

Center cut-out 4:3 from

16:9

4:3 (center)


1010 16 9 into 4 3 protected letterbox
1010 – 16:9 Into 4:3 Protected Letterbox

Letter-box 16:9 into 4:3

scan

16:9 (center)


1111 16 9 image with alternate 4 3 center
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



Consumer issues1
Consumer Issues

Broadcasters cannot rely on consumers to maintain aspect.

AFD is not widely implemented on consumer devices.


So what do we do
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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