There are quite a few digital channels transmitting widescreen programmes and movies for viewers with a widescreen television and the general trend is clearly towards the introduction of widescreen as the standard picture size for digital TV. The digital receiver will have an option in the set-up menu to select the type of television it is connected to – either 4:3 or 16:9 widescreen. The MPEG decoder in the receiver or set-top box is signalled when it is receiving a widescreen transmission and processes it in a way which is dependent on the display it is feeding. If the display is 16×9, no processing takes place but if the display is 4×3, the decoder will zoom or crop depending on its capability and on the viewer preference expressed in the installation setup:

  • it may take a centre cut-out, with the same height but severely cropping the sides
  • it may display a 16×9 letterbox, with all the picture but with large black bands top and bottom
  • it may crop a bit off either side, taking the ratio aspect down to just 14:9, leaving somewhat thinner black lines top and bottom
  • it may automatically distort a 14:9 cropped picture to fit a 4:3 screen.

In the UK the term “anamorphic” is used to differentiate a 16×9 widescreen picture which fills the whole frame, from a 16×9 letterbox with blank lines at the top and bottom of the frame. In the USA the terminology used is 16×9 full frame and 16×9 letterbox respectively.

 

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