4

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.
Angle
1
2
3
4
Mixed-angle track with stream 3 playing
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.
409Chapter 17 Creating and Editing Tracks