witf Blog

“Why is WITF’s image cropped on my screen?”

Written by Ron Kain | Mar 9, 2010 2:11 PM

This is one of the frequently asked questions fielded by our customer service and technology staff at WITF.  But there isn’t a simple answer.

Until the advent of high definition technology, television programs were produced with a 4x3 aspect ratio (meaning that the screen was 4 units wide to 3 units tall).  Since the advent of high definition programming, television sets and shows have been produced with a 16x9 aspect ratio, which is also the ratio used for films in movie theatres and for digital high definition programs.

Therefore, stations such as WITF have a wide mixture of programs—some older programs produced in a 4x3 format and new national content produced in 16x9.  This mixture of content, combined with the television broadcast “supply chain," are the fundamental reasons that shows often appear awkwardly shaped or cropped on your screen at home. It can often times create an awkward viewing experience on analog tiers of cable/satellite and fiber systems.

What’s a “television broadcast supply chain"?  It’s all of the equipment that a program passes through on its journey from the broadcast station to the home user’s television set.  In between a program might pass through a satellite transmission, a computer storage server, microwave transmission and other distribution gear, depending on how you receive the signal in your home.

In an ideal world, every piece of equipment in this chain would be able to detect the program’s aspect ratio—and adapt the display of the image to each aspect ratio. There’s a “marker” called the Active Format Descriptor (AFD) flag which does just that.

WITF is fortunate that, through the generous support of a WITF donor and technology enthusiast, we have been able to purchase the equipment to correctly capture and re-transmit this aspect ratio information for new programming.  This has corrected the aspect ratio on about 90% of the programming WITF transmits, especially during prime-time.  Unfortunately, there is still older programming in the archives as well as some national shows that do not have this information embedded which can wreak havoc on consumer television sets!

The issue is further complicated by the cable, satellite, and fiber delivery systems.  For display on the basic tiers of these subscription services, providers such as Comcast, Verizon, and Dish Network will “center cut” WITF’s 16x9 digital feed so that a 4x3 image will be displayed on their system. “Center cut” means removing the edges of the image all around so that the 16x9 image will “fit” into a 4x3 shape.

Center cutting often cuts off  graphics or material that are formatted outside of the 4x3 area that is being transmitted to you. Most national PBS producers are aware of this practice “center cutting” and try to produce their programs so that graphics are kept to the center of the screen. But we still have weekly examples of programs getting center-cut.

We are hopeful that these technology-transition issues will resolve themselves in time. Generally speaking, if you have a 16x9 television and receive programming over the air via an HD subscription service, WITF’s programming should look okay except for the few cases where older content is being broadcast.

If I can be of any assistance, please feel free to contact me directly or by commenting below.

Later this month, I hope to share a behind the scenes look of the digital translator installation taking place at the same site we transmit 93.3 from in Chambersburg!

Ron Kain
Senior VP and Chief Technology Officer

Published in witf blog

back to top