Being Mindful of Video Broadcast Down Conversion

Did you know that the majority of the US viewership is actually watching in SD? A recent Nielsen study states that nearly 86 percent of US households own at least one HD television set. However, only 36 percent of these households are actually watching “true HD,” defined as tuned in to the proper channel for an HD signal with an appropriately connected HD set-top box via HDMI or component cables.

With that in mind, 64 percent of viewers are actually watching television in an SD 4:3 ratio – even on their 16:9 HDTVs. Yes, SD television is still alive and well.

Down Conversion Options

In order for the individual stations to accommodate a feed for both HD & SD audiences, HD images will need to be down-converted. How the stations will handle the down-conversion of your HD master is their decision, not necessarily yours.

It can happen in two different ways:


This is the process of taking the full 16:9 master and fitting it into a 4:3 image without cropping any of the picture. In order to fill the screen, both the top and the bottom of the image will be filled with black bars.

letterboxed 16x9

A letterboxed 16:9 image

Not a preferred method of down conversion by any stretch. The SD feed aired on a widescreen television will leave the image floating in a sea of black, or “postage stamped.”


The "postage stamped" effect on an HDTV


4:3 letterboxed image on an old tube TV set

Another important disadvantage of this method of down conversion is that with the downsizing of your image, so are the critical on-screen graphics and important font sizes. If you were implementing the minimum font pixel height in your program’s legal disclaimer, well, it’s below that requirement now and will be illegal. Even that important phone number or website you need your viewers to visit to get a hold of you; unreadable now.

Most importantly, letterboxing an HD program may cause post-produced closed captioning to lose its on-screen placement to comply with FCC Rules & Regulations since captioning placement is set within that caption data, not the picture data.


The preference of the major US networks is that they want their SD viewers to continue to receive programming that fills their 4x3 screens. To facilitate this the stations automatically perform what’s called a “center-cut” on the HD content when playing out to broadcast making this the more common and regularly encouraged approach to down-conversion. The 16:9 image is cropped to fill the full 4:3 aspect ratio from top to bottom. In order to pull that off, the left and right side of the picture is lopped off.


A 16:9 image on a standard widescreen HDTV

Whoops, it looks like you were using the entire widescreen real estate when you were shooting and editing for television broadcast. Here's why that's a problem when it gets center-cut...


The same 16:9 image center-cut for broadcast on a 4:3 TV set


And also broadcast on the SD signal of an HDTV

There goes your important information!

Suppose your final program is heading to broadcast on television. In that case, it is important to know how your content may actually be seen by your audience (both HD and SD) and how you can prepare your final cut so that it is optimized and looks the best in both formats.

How can you prepare? Follow us to our blog on The Importance of 4:3 Center-cut Safe.