Choosing an Aspect Ratio

The aspect ratio is the ratio of the width of the visible area of the video frame to the height of the visible area. Standard NTSC and PAL monitors have a picture aspect ratio of 4:3 (or 1.33, which is the width divided by the height). Some High Definition Television (HDTV) formats have a picture aspect ratio of 16:9, or 1.78.

The DVD specification supports both 4:3 and 16:9 sources, but it does not support HD video. Most HD video formats use a combination of features to create the high definition image, including a much larger frame size than DVD-Video supports.

HD-based DVDs also support both 4:3 and 16:9 sources, as well SD and HD video formats.

Using 16:9 sources in your project raises a number of issues that you need to be aware of. Your main goal is to ensure that 16:9 assets play back correctly on 16:9 monitors and as expected on 4:3 monitors (and that 4:3 assets play correctly on both monitor types as well). Incorrect settings can lead to distorted video. For example, the video may appear horizontally compressed (objects look “skinny”) or expanded (objects look “fat”).

This illustration shows the viewing options for a 16:9 asset.

Figure. Shows options for displaying 16 by 9 video on a 4 by three monitor.

This illustration shows the viewing options for a 4:3 asset.

Figure. Shows aspect ratio options for displaying 4 by 3 video on a 16 by 9 monitor.

Read the following sections to find out more about using 16:9 assets in your projects.

What Exactly Is a 16:9 Asset?

When you decide to use 16:9 assets in a DVD Studio Pro project, it is crucial that you understand exactly what attributes your 16:9 media should have.

16:9 and SD Projects

The DVD specification and DVD Studio Pro require 16:9 video to be anamorphic. An anamorphic 16:9 video frame has the same number of pixels as a 4:3 video frame. When displayed on a 16:9 monitor, the frame is horizontally stretched to fit the screen, and the content appears normal. When viewed on a 4:3 monitor, however, the video content appears horizontally compressed (see the illustrations in Choosing an Aspect Ratio).

The most common error is to letterbox your 16:9 video assets before bringing them into DVD Studio Pro. Once a 16:9 asset has been letterboxed, it becomes a 4:3 asset with black bars along the top and bottom of the video image. If you flag letterboxed source video as 16:9 video when encoding it, you will have problems when you play it back later.

16:9 and HD Projects

HD projects can use a wide variety of video resolutions. Several of these are true 16:9 (1280 x 720p and 1920 x 1080i) while several others use the same anamorphic method used in SD projects (720 x 480p, 720 x 576p, and 1440 x 1080i).

Using Pan-Scan to Display 16:9 Video

The pan-scan method of displaying 16:9 video on a 4:3 monitor was developed as a compromise between letterbox, which displays all the video content but with black areas at the top and bottom, and the only other alternative: filling the entire 4:3 screen, but cropping some of the content. With pan-scan, you can choose which bits of the 16:9 content to crop, ensuring the action is not lost by displaying the center of the screen only. The pan-scan method can result in sudden jumps from one side of the screen to the other (for example, to follow a conversation’s dialogue), which may make your video look as if edits have been made.

To make pan-scan work, you must have a pan-scan vector, a frame-based value that controls which part of the content to use. Someone watching the video creates the vector, deciding which parts should be seen. This vector must be available when the video is MPEG-encoded. The MPEG encoder included with DVD Studio Pro does not support pan-scan vector information. However, if the information is already part of an MPEG-encoded video stream, created with an encoder that supports the vector information, DVD Studio Pro passes this information along.

Virtually all movies shown on TV have been through the pan-scan process; however, pan-scan vectors are rarely used for movies released on DVD. Instead, a version of the movie is made using the 4:3 pan-scanned source and is not intended to be played as a 16:9 video on 16:9 monitors. The other side of the disc often contains the true 16:9 version, set to display as letterboxed video on 4:3 monitors.

Important: Do not use pan-scan if your video does not actually support it. If you do, only the center part of the frame will appear.

MPEG Encoding and 16:9 Video

It’s important to correctly identify your source video as either 4:3 or 16:9 before encoding it. At this point, you are only identifying it—you are not defining how it should be handled when played back. When using the integrated MPEG encoder, you can select the video’s aspect ratio in the Encoding pane of DVD Studio Pro Preferences.

Using 16:9 Assets in Tracks

Each track within a DVD Studio Pro project has an aspect ratio setting. This setting lets the DVD player know how to display the video when playing back the title.

With a 16:9 track, you specify how it will play back on a 4:3 monitor: Pan-Scan, Letterbox, or Pan Scan & Letterbox (allowing the viewer to choose). As mentioned previously, pan-scan is rarely used and should never be selected unless the encoded video contains pan-scan vector information.

Mixing 16:9 and 4:3 Assets in a Track

Keep in mind that a track’s aspect ratio setting applies to the entire track. If you mix 16:9 assets with 4:3 assets in a track, you will have problems when playing it back. For example, if you set the aspect ratio to 16:9 Letterbox, the 4:3 video will also be letterboxed and end up looking vertically compressed.

To be safe, do not mix 16:9 and 4:3 assets in the same track. Instead, create separate tracks for each. You can use the Connections tab in DVD Studio Pro to control the playback order of the tracks.

Some Players Cheat!

Unfortunately, not all players handle 16:9 video correctly. The aspect ratio setting for each track is stored in the track’s video title set file (vts_01_1.vob, for example). Most DVD players read the setting and process it correctly, but some DVD players ignore this setting and instead look at the aspect ratio setting of the video itself. For the most part, this works out, but it can result in inconsistencies when playing the title on different DVD players, particularly if you are not careful while encoding and authoring.

Buttons over 16:9 Video Tracks

To place a button over a video track, you add a menu overlay to a subtitle stream in the track. These overlays are not processed in the same way as the video, so you must create a separate overlay for each display mode (16:9, 4:3 letterbox, and 4:3 pan-scan). You then need to create a script that selects the correct subtitle stream to display based on the DVD player’s settings.

See What Happens with Different Aspect Ratios? for information on using subtitle streams to place buttons over a video track, and see Creating Scripts for information on creating scripts.

Using 16:9 Assets in Menus

Typically you’ll want to use 16:9 menus with 16:9 tracks. Most of the same concerns with video apply to menus as well—specifically how the 16:9 menu is displayed on a 4:3 monitor.

With a 16:9 menu, you specify how it will play back on a 4:3 monitor: Pan-Scan, Letterbox, or Pan Scan & Letterbox (allowing the viewer to choose). As mentioned previously, pan-scan is rarely used, and should never be selected unless the encoded video contains pan-scan vector information.

See Understanding Pixel Differences in Graphics and Video for information on the image size settings you should use when creating 16:9 menus.

Issues with Film Aspect Ratios

While 16:9 is a fairly wide aspect ratio, it is not wide enough to contain an entire frame from a typical Hollywood movie. Two film aspect ratios are widely used now: Normal is 1.85:1 and Widescreen is 2.40:1 (for comparison, 16:9 is 1.78:1). For normal titles (those that use the 1.85:1 aspect ratio), a small amount of letterboxing or pan-scan cropping is required to transfer the title to DVD, but for Panavision titles significant letterboxing or pan-scan cropping is necessary. This processing must be done before the video is MPEG-encoded. The DVD specification supports only 4:3 and 16:9 aspect ratios.

Figure. Shows the relative aspect ratios of 4 by 3, 16 by 9, normal film, and widescreen film formats.

You should not be surprised to see some letterboxing when playing a Panavision movie on a 16:9 monitor.