Source Frame Aspect Ratio - evertz 7710ARC Series Manual

7700 MultiFrame Manual
7710ARC Series - SD Aspect Ratio Converter

6.2.1.1. Source Frame Aspect Ratio

The Source frame Aspect Ratio is the ratio of the horizontal dimension to the vertical dimension of the
maximum active picture area permitted in a video signal when displayed so that images, that completely
fill the source frame, will retain their original shape.
In the most general case, the Source frame lattice is simply a two-dimensional array of pixels used to
transport a sequence of images. The aspect ratio of the intended display device must be known when the
image is placed into the source frame lattice to accurately display the source frame without distortion of
the original image.
For example, HD video is commonly down converted using an anamorphic process that takes the full HD
raster and places it over the full SD raster. A circle contained within the HD source video will be seen as
an ellipse in the SD video, unless viewed on a 16:9 SD monitor. In this example, the SD video's source
frame aspect ratio is 16:9.
Another example is in film to tape transfers where the film image may have an aspect ratio of 2.40. A
telecine may take this video and anamorphically compress it into a 1080i/59.94 video raster. Therefore, if
the film contained a circle after it is transferred to 1080i/59.94 video, the circle will look like a tall thin
ellipse. In this case, even though SMPTE274M specifies an aspect ratio of 16:9 for 1080i/59.94 video, the
source frame aspect ratio is 2.40.
7710ARC-11
Revision 1.1