User guide

DivX Plus Player for Windows
27
DivX, LLC User Guide
Aspect ratio in digital video refers to the fraction of the height
and width of pixels measured from the video’s resolution. This
does not measure the actual amount of pixels or length, so two
videos with different resolutions could have the same aspect
ratio. The most common aspect ratios are 4:3 (universally used
for standard-definition) and 16:9 (universally used for high-
definition).
The Pixel Aspect Ratio, or PAR, measures the actual height and
width of the pixels. The Display Aspect Ratio, or DAR, refers
more specifically to the shape of the image frame in a video.
Unlike PAR, this can result in a different shape than the pixels
would otherwise indicate. One common reason this is used is in
Anamorphic encoding, where the pixels of a video are stretched
over a larger frame size when displayed. So a digital video file
that has a resolution of 720x480, but is flagged with a DAR of
16:9, will play back in widescreen without changing the pixel
count. This is often what causes videos to show with letterbox
or pillarbox.
BITRATE, FRAME RATE, AND FPS
The Bitrate indicates the size of a video or audio stream over
time, usually calculated in Kilobytes per second.
The Frame rate tells us how many images of a movie are
displayed for every second a movie is played. A high frame rate
would therefore have more frames per second, and a larger
file size, for the same film of a lower frame rate. Frame rate is
measured in ‘frames per second’ or fps. In the NTSC system,
the frame rate is usually about 29.9 fps, and in PAL it is usually
25 fps.
Incorrect DAR
for standard definition
(16:9 video on 4:3 display)
Correct DAR
for widescreen
(16:9 video on 16:9 display)
Letterbox occurs when
DAR is wider than display
Pillarbox occurs when
DAR is narrower than display