Pixel and screen aspect ratios
Digital video uses two types of aspect ratios: pixel aspect ratios and screen aspect ratios (also referred to as frame aspect ratios). Although related, they describe distinct properties. The pixel aspect ratio describes the pixel dimensions within the screen, while screen aspect ratio details the screen dimension relationship.
Pixel aspect ratios
Pixel aspect ratios describe the width-to-height ratio of the pixels that make up a video or still-image file. Pixels are either square or nonsquare (rectangular). Square pixels have a ratio of 1:1. In the film and video industry, however, the :1 is dropped and ratios are expressed as a single number. The following table lists the nonsquare pixel aspect ratios for the two TV standards for standard-definition video.
Fullscreen pixel aspect ratio
Widescreen pixel aspect ratio
- 4:3, or
- 16:9, depending on whether it has a pixel aspect ratio of
- 0.9, or
The type of pixels in an image, combined with its dimensions, determine its screen aspect ratio. An NTSC 720 x 480 pixel video, for example, displays as widescreen if it contains nonsquare pixels with a ratio of 1.22. This video displays as a regular 4:3 screen if it contains nonsquare pixels with a ratio of 0.9. Encore lets you specify the pixel aspect ratio of imported assets.
High-definition video and still images have either square 1:1 pixel aspect ratios or a 1.333 anamorphic pixel aspect ratio. They come in three sizes (1280 x 720 or 1920 x 1080 with square aspect ratios, and 1440 x 1080 pixels with anamorphic aspect ratios), and fit in a 16:9 screen aspect ratio.
Screen aspect ratios
Screen aspect ratios (also known as frame aspect ratios) describe the width-to-height ratio of an image or device. A standard television has a 4:3 ratio (referred to as fullscreen), and a widescreen television has a 16:9 ratio. These ratios are also noted as 1.33 for fullscreen (4 / 3 = 1.33) and 1.78 for widescreen. (Film, which includes a majority of widescreen content, actually uses screen aspect ratios ranging from 1.66 to 1.85, or even 2.35 for scope footage. However, these all work well within the format and can be considered widescreen.)
About still-image pixels
Most digital still cameras and graphic applications use square pixels. You should set the pixel aspect ratio of still-image assets to square to ensure that they display correctly. An exception to this rule are files created in Adobe Photoshop® CS3 and Adobe Photoshop CS2. Photoshop lets you work in nonsquare pixels when creating images for DVDs and video. Use the Photoshop preset that matches your project. For example, if you’re working with NTSC DV footage at 720 x 480, you’d use the NTSC DV 720 x 480 (With Guides) preset.
Specify an asset’s pixel aspect ratio
You can mix assets with different pixel aspect ratios in the same project. Encore interprets each asset’s pixel aspect ratio on import. Occasionally, an asset may contain incorrect information which, in turn, prevents Encore from identifying it correctly. If you need to change an asset’s pixel aspect ratio, you can use the Interpret Footage command to specify it.
Select the file in the Project panel.
Choose File > Interpret Footage.
In the Interpret Footage dialog box, select Conform To, and then choose the appropriate pixel aspect ratio:
Square Pixels (1.0) for a standard-definition or high-definition file created using square pixels.
SD NTSC (0.9091) or SD PAL (1.0940) for a standard-definition file created using nonsquare pixels with an aspect ratio of 0.9091 (NTSC) or 1.0940 (PAL).
SD NTSC Widescreen (1.2121) or SD PAL Widescreen (1.4587) for a standard-definition file created using nonsquare pixels with an aspect ratio of 1.2121 (NTSC) or 1.4587 (PAL).
HD Anamorphic (1.333) for a high-definition file created using nonsquare pixels with an aspect ratio of 1.333.
Specify the screen aspect ratio
Encore determines the screen aspect ratio for you. You can, however, change it if necessary. The type of asset determines how you specify the screen aspect ratio. For menus, and timelines containing still images but no video, you specify the screen aspect ratio in the Properties panel. For timelines with video, you specify the screen aspect ratio by setting the pixel aspect ratio of the video asset. However, in a DVD project, you must keep the same aspect ratio for the assets that share a timeline.
Select the menu or still timeline in the Project panel.
Click the desired screen aspect ratio (4:3 or 16:9) in the Properties panel.Note: When you change the aspect ratio in the Properties panel, Encore actually changes the asset’s pixel aspect ratio, which in turn affects the screen aspect ratio.
Widescreen content on fullscreen TVs
There are several different methods used to convert widescreen content to 4:3 format for display. Some of the methods convert the widescreen format to fullscreen format and store the converted fullscreen video on the disc. The preferred method stores the original widescreen video on the disc, and the player converts it as necessary during playback to a fullscreen device. Encore stores the original widescreen footage on the disc and instructs the player to letterbox it on playback to a 4:3 TV, regardless of the player’s settings.
DVD players use the following methods to convert widescreen video for display on a 4:3 device:
- Pan and scan
- Crops the widescreen video to fit the fullscreen frame. Pan
and scan loses the visual data outside of the 4:3 frame. Traditionally,
an editor or technician guides the pan-and-scan process during conversion
from film to TV formats. DVD players use an automatic pan and scan.
Automatic pan and scan (limited to horizontal tracking of the full
height of the picture) crops the image that is stored on the DVD
in widescreen format, and displays it on 4:3 devices.Note: If a set‑top DVD player is set to pan and scan, Encore overrides the player and displays the footage in letterbox format.
- Shrinks the image until it fits the 4:3 format horizontally
and displays black bars in the blank spaces at the top and bottom
of the frame. The resolution of the image is lowered, but the image
remains whole—no cropping occurs. DVD players use automatic letterbox
to display footage stored as widescreen on 4:3 devices.16:9 NTSC footage
- Displayed by a DVD player using the original widescreen format on a widescreen TV
- Using automatic pan and scan to crop the image on a 4:3 TV
- Using automatic letterbox to reduce resolution and display the entire image on a 4:3 TV