Adding Alternate Video Streams

One feature unique to the DVD medium is the viewer’s ability to switch between parallel video streams with continuous audio. Only one video stream at a time can serve as the active stream, but there can be as many as eight alternate streams, for a total of nine “camera angles.” These can be different camera views, or angles, of the same subject, or they can be any other video sources.

For example, a concert video could use different camera angles for the alternate video streams, with cameras focusing on each musician. Stream V1, the main video stream, could be an edited version of all angles while streams V2 to V9 could be unedited versions of each musician. This would allow the viewer to choose whether to see the whole concert or focus on a specific aspect of it.

In another example, the V1 stream could contain the normal view of a business presentation, including the presenter, and the presentation’s slides could be displayed up close on the V2 stream.

Multi-Angle and Mixed-Angle Tracks

DVD Studio Pro allows you to create either multi-angle or mixed-angle tracks. With a multi-angle track, the alternate video streams are the same length as the main stream. A mixed-angle track uses partial alternate video streams.

Authoring with multi-angle video is an exciting capability of the DVD medium, though there are some disadvantages, the main one being that multi-angle video streams consume a great deal of disc space. A DVD capable of holding 120 minutes of video has its play time reduced to 60 minutes if there are two video angles (120 divided by 2), and to 13.3 minutes if there are 9 video angles.

A space-efficient method of taking advantage of the alternate video streams is to build DVD projects that have a single video stream for most of their playing time, but that provide alternate streams in certain sections. This is known as using mixed angles.

Figure. Example of a mixed-angle track jumping between streams 1 and 3.

About Alternate Stream Video Assets

If you want to switch between video streams while the DVD is playing, the DVD specification sets some restrictions on the alternate streams. They must be in the same MPEG format and have the exact same GOP structure as the main stream. It is strongly recommended that you use the same encoder for all streams to ensure they match exactly.

For multi-angle tracks, all streams, including the main one, must be the exact same length.

For mixed-angle tracks, you use markers to define one or more sections of the main stream that contain the alternate streams. There are three basic rules for the alternative sections:

  • Within a track, you can use markers to define multiple sections to use additional angles, but each section must have the same number of streams. For example, you cannot have one section early in the track with two alternate streams and a section later in the track with three alternate streams—both sections must have either two or three streams.

  • Each alternate angle section can be different lengths, but all streams within a section must be the same length. For example, you can have one mixed-angle section early in the track that is 10 seconds long and a second mixed-angle section that is 20 seconds long. All alternate streams in the first mixed-angle section must be 10 seconds long; all alternate streams in the second mixed-angle section must be 20 seconds long.

  • You cannot use still images in the V2 through V9 streams. You can use still images in the V1 stream as long as they are outside of the mixed-angle areas (places where video is present in the V2 through V9 streams).

See Encoding Video for Multi-Angle Tracks for more information on stream requirements.

Creating a Multi-Angle Track

To create a multi-angle track, you need to use two or more suitable video assets that are the exact same length and have the same GOP structure.

To create a multi-angle track
  1. Configure the Track Editor so that you can see as many video streams as you intend to use. See Viewing the Streams for details.

  2. Add the main video asset to the track’s video stream 1 (V1).

  3. Add the second video asset to the track’s second video stream (V2).

  4. Continue adding video assets to the next available streams until they are all in place.

You can name each clip in each stream using the Clip Inspector.

Creating a Mixed-Angle Track

With a mixed-angle track, the main video stream runs the full length of the track with the alternate streams using only a small part of that time. Each of the track’s alternate video streams is aligned to a marker, and all corresponding alternate video assets start at the same point.

Each alternate stream must use assets with the same length, and their GOP structures must match the main video stream.

To create a mixed-angle track
  1. Configure the Track Editor so that you can see as many video streams as you intend to use. See Viewing the Streams for details.

  2. Configure the V1 stream as needed. If you are adding multiple clips or still images, place them all and make any necessary adjustments before adding anything to streams V2 through V9.

  3. Create a marker where you want the first mixed-angle portion to begin.

  4. Add the second video asset to the track’s second video stream (V2) at the marker.

    The asset snaps to the marker. Use the timeline zoom control to verify the asset is positioned properly.

  5. Continue placing video assets to the next available streams until they are all in place and lined up with the marker.

  6. Add a marker at the end of the angle clips by Control-clicking the clip in the V2 stream and choosing Add Marker to Clip End from the shortcut menu.

  7. If you are adding an additional mixed-angle section to the track, add another marker and repeat steps 3 through 6.

You can name each clip in each stream using the Clip Inspector.

Important: To avoid errors when building your project, do not edit the V1 stream (add, trim, or remove assets) once you have added assets to the V2 through V9 streams.