The digital video aspect of 16:9 was chosen as a compromise size to best accomodate the various widescreen sizes in use in the film industry. Most modern films use a ratio of 1.85:1 which is somewhat flatter than 16:9 (1.78:1). The motion picture industry uses a variety of display aspect ratios, ranging from the nearly 4:3 "Academy" ratio of 1.37:1 used up until the 1950s, to extreme widescreen formats such as Panavision, VistaVision, or CinemaScope at 2.39:1 or even 2.67:1.
#FATAL FRAME 4 TRANSLATION 4.3 TV#
These newer HD formats are therefore not anamorphic.Ĭonversion of film and TV to digital video As a result, the DAR and SAR aspect ratios are the same and the PAR aspect ratio is 1:1. all store HD video in the native frame size. More recent HD storage formats such as AVCHD, Blu-ray, DNxHD, ProRes 422, etc. All of these formats therefore use non-square pixels with PAR pixel aspect ratios that are not 1:1. Because of data rate limitations, these formats may not necesarily store video in native 16:9 formats, but instead may use squeezed anamorphic formats. These include formats such as DVCPRO-HD, HDV, HDCAM, XDCAM, etc. During the transition to HD, however, several "high-definition" compression formats were introduced for camcorders. Since the video DAR display aspect ratio is either 4:3 or 16:9, the pixels are non-square and the PAR is not 1:1.įor HD video, the DAR display aspect ratio became fixed at 16:9. These correspond to SAR values of 3:2 and 5:4 respectively. SD video for these formats is typically stored with a frame size of 720x480 pixels (NTSC video) or 720x576 pixels. This is mostly because of the widespread use of SD compression formats such the DV camcorder formats and DVD discs. high definition video storage and compressionĪnamorphic video with non-square pixels is more of an issue for Standard Definition (SD) video rather than for High Definition (HD) video. Since DAR = SAR * PAR, in the second case above with a DAR of 16:9 and SAR of 3:2, the PAR is 32:27. If the pixels are non-square, then the PAR is not 1:1 and acts as a correction factor for the SAR. If pixels are square, then the PAR is 1:1 and DAR = SAR as in the first case above. The pixels of the stored video are considered to be either square or non-square. In digital video, the pixels used on a display are considered to be square (i.e. The basic relationship between the three apect ratios is DAR = PAR * SAR. To correct for it, we introduce the third type of aspect ratio, the Pixel Aspect Ratio (PAR). The latter situation is often referred to as "anamorphic" video. The stored video must be stretched horizontally or squeezed vertically to match the display correctly. The SAR is 720:480 = 3:2, an aspect ratio which does not match the 16:9 display. An example of this might be a 16:9 display showing video stored with a frame size of 720 x 480 pixels.
Here the process of displaying the video involves distorting the stored video ratio SAR to make it match the desired viewing aspect ratio DAR. In other cases, the video may be stored with an aspect ratio SAR that does not match the display.
An example of this might be a 16:9 display showing video stored with a frame size of 1280x720 pixels. If the viewing aspect ratio, the DAR, matches the SAR, then the process of the displaying the stored video is simply a matter of proportionally scaling it to the correct size. When digital video is stored into a file or on a disc, it is stored with a particular frame size and aspect ratio, the SAR. We will try to clarify here how these three aspect ratios work and what role they play in digital video.Īnamorphic video and square vs. There are, however, two other kinds of aspect ratio that play an important role in digital video: the Pixel Aspect Ratio (PAR), and the aspect ratio of the stored data which we will call the Storage Aspect Ratio (SAR). Typically, this ratio is 16:9 (widescreen) or 4:3 (full screen). This is the ratio of the width to the height of the display frame for the video, the aspect ratio of what we see. The kind of aspect ratio most people know is the Display Aspect Ratio (DAR). The role of aspect ratio in digital video has caused quite a bit of confusion, partly because there are actually three types of aspect ratio, not just one.