1. St. Paul Public Television Quality Workshop - July 8-9, 2010
Aspect Ratio and Active Format Description How do we make it all fit? Gerry Field American Public Television
St. Paul Public Television Quality Workshop - July 8-9, 2010

2. Aspect Ratio Television Aspect Ratio Defined:
Picture frame: Ratio of image width to image height.
Not directly tied to resolution.
HD Screens are typically 16:9.
SD Screens are both 4:3 and 16:9.
Programming is varied.
16:9, 4:3, 15:9, 14:9, 1.85:1, 2.39:1 etc.
Mixed aspect ratio programs

3. 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.
U.S. homes with three or more TV sets: 54%

4. 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 crop other formats
Upconversion, Downconversion

5. 4:3 Image in a 4:3 Display

6. 16:9 Image in a 16:9 Display

7. But…How do we make it all fit?
4:3 upconverted to 16:9
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.

8. 4:3 Image in a 16:9 Frame

9. But…How do we make it all fit?
16:9 downconverted 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.

10. 16:9 Image “Letterboxed” in 4:3 Frame

11. But…How do we make it all fit?
16:9 can also be “Center Cut”
Downconverted 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.

12. 16:9 Image

13. 16:9 Center Cut in 4:3 Frame

14. However…..
Center Cut is only feasible if all active elements and graphics are maintained in the 4:3 center of the 16:9 image.
“Center Cut Safe” – Action and Titles

15. 16:9 Image in a 16:9 Display

16. 16:9 Image center cut to 4:3

17. Worst Case 4x3 Letterbox up converted to 16:9
Then down converted using a 16:9 to 4:3 down converter.
“Postage Stamp”.

18. 16:9 Image in a 4:3 Display

19. Up Converted to 16:9 as 4:3

20. Down converted 4:3 Letterbox

21. What is the proper way to treat this?
It depends.
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.

22. Anamorphic Commonly defines 16:9 “squashed” into 4:3
(Can also apply to 4:3 “stretched” to 16:9)
Used as a distribution technique
Most common is SD widescreen on D-Beta
Must be properly handled prior to emission
If not, viewer sees “squashed” picture

23. Full Screen 16:9

24. Anamorphic 4:3

25. Anamorphic Anamorphic or 16:9 SD programming may be
upconverted to 16:9 HD and distributed (at a bandwidth cost).
Alternatively, 16:9 SD can be distributed with MPEG2 encoder flag set to 16:9.
16:9 SD included in ATSC A/53 standard.
SD 16:9 can co-exist with SD 4:3
Member station IRD will output correct format as desired.

26. If the MPEG2 flag is set to 16:9 at the MPEG2
Encoder, the Sencore IRD will properly recognize
The format and provide properly formatted video
16:9 HD or 16:9 SD
Sencore IRD
MRD3187
4:3 SD Center Cut
Source SD 16:9
4:3, 16:9 Letterbox SD

27. Down Converting Some stations and channels are still SD only.
50 % of our viewers are still SD.
Most HD households still have 2nd and 3rd SD sets.

28. 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.

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

30. 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)

31. AFD = ‘1000’ (Full Frame) In a 4:3 coded frame In a 16:9 coded frame31

32. 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 32

33. AFD = ‘1010’ (Protected 16:9) In a 4:3 coded frame33

34. AFD = ‘1111’ (Center Cuts) In a 4:3 coded frame In a 16:9 coded frame34

35. Consumer Issues

36. Consumer Issues
Broadcasters cannot rely on consumers to maintain aspect.
AFD is not widely implemented on consumer devices.

37. 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.

38. Questions? / Comments