Letterbox and pillarbox
Letterbox and pillarbox denote processes in image processing and video technology in which black borders are usually added to an image. The aim is to adjust the aspect ratio of an image, e.g. B. to the aspect ratio of a screen . With letterbox, bars appear at the top and bottom. The other direction is called pillarbox; the bars are on the right and left, such as B. when converting a picture from 4: 3 to 16: 9 . These techniques serve as an alternative to non-proportional distortion of the image.
Naming
The name “letterbox” refers to the shape of the openings in mailboxes. The name “Pillarbox” is derived from the columnar mailboxes common in Great Britain.
Pillarbox on German television
While HDTV - Simulcast -Testbetriebes of ProSieben was except for the announced high-resolution movies normal SDTV signal of 720 × 576 (9 16) (4 3) pixels on HDTV resolution of 1920 × 1080 pixels scaled up. The films in 4: 3 format and even the films in 16: 9 including letterbox were scaled up to 1440 × 1080 pixels and then brought to a resolution of 1920 × 1080 using the pillar box bars. In the meanwhile discontinued regular operation of Sat.1 HD and ProSieben HD from October 26, 2005, pillar boxing was used again, but the unused pillar box bars were enriched with additional information.