In the old days of DVD authoring (that would be just two or three years ago), DVD tools required that you first use a separate application to transcode all your assets into DVD-compliant formats before you could import and use them in the DVD authoring tool. While Encore now does this transcoding automatically for you, allowing you to import the file types shown earlier, there are still times when it makes sense to do the transcoding first. For example, if you plan to keep a clip around on disk and use it in multiple projects, you’ll probably want to transcode it once, and then store the smaller MPEG file on disk so you can reuse it without any further processing or duplicating disk space.

Figure 3-4. Importing other video files into Encore.

If you import your own MPEG-2 file, Encore will check it for compliance with the requirements of the DVD specification (including resolutions and a subset of the full generality of the MPEG syntax). If the file is DVD-compliant, Encore can use it directly in the project without transcoding. Otherwise, Encore will transcode it (if possible) just like any other noncompliant file.

You can import DVD-compliant MPEG-2 material in two ways:

To import a DVD-compliant MPEG-2 clip, use the File → Import as Asset option. In the file dialog, select Files of Type, MPEG Video. Once the file is imported, note that Encore lists the file type as “MPEG video” inside the Project tab, and places the words “Don’t Transcode” under the Transcode Settings. This means that Encore has confirmed that the file is DVD-com-pliant and will not have to be transcoded. See Figure 3-5.

Figure 3-5. Import MPEG-2 video clips that are already DVD-compliant.

Here’s an interesting question: if the MPEG-2 output of Encore—the video frame stored on a DVD disc—is a fixed size for video, how do we generate both regular and widescreen video images? To better understand this, we need to introduce two new concepts: screen aspect ratios and pixel aspect ratios.

Let’s take a look at screen aspect ratios—sometimes called display aspect ratios—first. As we saw in Chapter 2, regular television has a screen aspect ratio of 4:3. That is, the entire display screen itself is rectangular: four units (just pretend that those units are squares of some size) wide and three units high. Most of the televisions available today, as well as those sold over the past 50 years or so, use a 4:3 aspect ratio, which is often called a fullscreen aspect ratio. Newer, widescreen televisions, on the other hand, have also gained favor with consumers over the past few years, as they simulate the theatrical aspect ratios of feature films. These televisions have a 16:9 aspect ratio, which is often known as a widescreen aspect ratio.

DVD video frames are stored at the same image resolution (720 x 480 for NTSC or 720 x 576 for PAL) whether the video is intended for standard or widescreen display. But that doesn’t mean that they should be displayed at that resolution. In fact, if you view these raw DVD images on a computer, they will look distorted—a raw DVD frame intended for a widescreen presentation will look horizontally squished, and a raw DVD frame intended for fullscreen display will look slightly stretched.

Correcting these problems is where the pixel aspect ratio comes in. To make these images work in both fullscreen and widescreen television formats, you need to adjust the aspect ratio of each individual pixel. So, for example, if you want to create a 16:9 screen aspect ratio out of a 720 x 480 image, you’ll need to set the pixel aspect ratio to favor a pixel that is wider than it is tall. And if you want to create a 4:3 screen aspect ratio out of a 720 x 480 image, you’ll need to use a pixel aspect ratio that is slightly taller than it is wide. See Figure 3-6.

Figure 3-6. Creating fullscreen and widescreen video by varying the pixel aspect ratio (NTSC).

Table 3-4 shows the approximate pixel aspect ratios used to convert standard NTSC and PAL resolutions to fullscreen and widescreen television screen aspect ratios.

A DVD can contain material intended for both fullscreen and widescreen aspect ratios. DVD players are designed to correct the output video to display properly, whatever the output display device may be. For example, with a standard television, a DVD player may “letterbox” the video by placing black bars at the top or bottom. In the same manner, a DVD player may show a standard resolution video on a widescreen display with black areas on each side. Of course, this requires that the DVD player be set up to provide the correct type of output for the actual display device. Today’s display monitors also provide additional options for specifying how different input video signals can be reformatted on the display.

In general, the DVD author is responsible for preparing any widescreen video clips or menu images at the appropriate aspect ratio, and then properly marking them as widescreen when authoring them onto the DVD. You can specify the display aspect ratio of video clips when they are encoded into MPEG format, whether within Encore (using a transcode preset), or in an external program such as Adobe Premiere Pro.

When the DVD is played, the display can switch from standard to widescreen aspect ratio as playback moves between different menus and video. You will often see this on commercial movies, for example, when moving from the main feature film (in widescreen) to additional videos and documentaries (often in standard aspect ratio).

The bottom line is that the amount of pixel data stored is the same whether it contains standard or widescreen aspect ratio images. It’s your job to keep track of how that data is to be interpreted, and then make sure that you use the appropriate settings for the devices and software that you use. When you shoot widescreen video with a DV camcorder, you capture the same amount of pixel data for each frame, but use a different camera lens to squeeze a wider horizontal view into a 720 x 480 array of sensors. Then when you capture and edit the DV video, as long as your software applications understand that this is widescreen video, they can display and process it for you at the correct aspect ratio. Similarly, when you author DVDs in Encore with widescreen video, Encore can ensure that the video on the DVD is identified properly so that the DVD player outputs it in the correct format for display.

By default, Encore encodes audio clips to your choice of one of three audio formats supported by the DVD specification. The DVD-compliant audio formats are shown in Table 3-6. As with video, if you import audio files that meet the formats and constraints listed, Encore will not need to transcode them.

Encore allows you to select a default audio encoding for the entire project to one of the standards in Table 3-6. To set this default, select Edit → Preferences → Encoding. Note that this will override the setting for individual clips, including DVD-compliant audio assets. In other words, if the default audio encoding format is set to Dolby Digital, Encore will still transcode audio assets that are already DVD-compliant (e.g., PCM or MPEG) to Dolby Digital.

In general, I recommend using Dolby Digital (AC-3) encoding for the best-quality compression. Compared to PCM, Dolby Digital also will significantly reduce the size of the audio on your discs, freeing up room for more material.

Remember that computer displays have square pixels, or a 1:1 pixel aspect ratio. Television displays have rectangular pixels, with either a 4:3 or 16:9 aspect ratio. So, if you import a still bitmap with a perfectly round circle on a computer display, transcode it to a DVD, and display it on a television set, the circle will appear as either a wide oval on widescreen televisions, or a slightly squished circle on standard televisions. The effect can be hard to ignore when you have familiar objects such as faces or circular signs, especially on a 16:9 display.

One way to correct for this is to edit a still image on a 4:3 or 16:9 grid of square pixels, and then scale the result down to the standard DVD resolution. This is often done by scaling only one dimension of the image, in order to minimize the scaling artifacts. If you want to go this route, create and edit the image at the target resolution shown in Table 3-8, then scale the graphic down to the DVD resolution, based on your broadcast standard.

If you have Photoshop CS, you’re in luck: you can edit a still image and see exactly how it will look by selecting the target pixel aspect ratio (Image → Pixel Aspect Ratio). This will “stretch” the image for you while you’re working on it, so you can see exactly what it will look like when displayed on a television. Remember that this is just a preview, only for display purposes; your image isn’t really the resolution that it appears to be. If you want to see the true resolution of the image, you can return to square pixels at any time by choosing Image → Pixel Aspect Ratio → Square. See Figure 3-8.

Figure 3-8. Changing the pixel aspect ratio in Photoshop CS.

If you want to adjust the pixel aspect ratio for an imported image in Encore, select the image in the Project window and choose File → Interpret Footage. Then, choose the desired aspect ratio for the image. This is useful when you want to reuse the same graphic image for both standard and widescreen displays.