Inside Macintosh: QuickTime Reference

The track class

QuickTime stores data separately in tracks. Tracks indicate what kind of data a movie contains. Examples of track types include video, audio, and text. The track class provides access to useful information about a track, such as name, kind, start time and duration. Some properties can be set, such as name, and enabled (which determines whether a specific track plays when the entire movie plays).

Class track: A track in a QuickTime movie.

Plural form:

tracks

Properties:

class type class [r/o]

-- the class

name international text [r/o]

-- the name of the track

start time integer

-- the time delay before this track starts playing

duration integer [r/o]

-- The duration of the track

kind string [r/o]

-- the kind of media in the track

dimensions point

-- the current dimensions of the track

natural dimensions point [r/o]

-- the dimensions the track has when it is not scaled

enabled boolean

-- should this track be used when the movie is playing?

id integer [r/o]

-- the unique identifier for this track

layer small integer

-- the layer of the track

language international text

-- the language of the track

visual characteristic boolean [r/o]

-- can the track be seen?

audio characteristic boolean [r/o]

-- can the track be heard?

sound volume small integer

-- the volume of the track [0..255], where 256 is 100 percent

sound balance small integer

-- the balance of the track [-127..128], where negative is left, 0 is center, and positive is right

Some examples of how you would use various properties of the track class:

-- set track name --

set name of track 1 of movie 1 to "hip cats"

-- set enabled of track --

set enabled of track 1 of first movie to false

-- get enabled state of all tracks --

get enabled of tracks of movie 1

-- set track dimensions --

set dimensions of track 1 of movie 1 to {320, 240}

-- get the track data size --

get the track data size of track 1 of movie 1

get the track data size of tracks of movie 1

-- get name of tracks --

get name of tracks of movie 1

-- get natural dimensions of track--

get the natural dimensions of track 1 of movie 1

-- get id of track --

get the id of track 2 of movie 1

-- get layer of track --

get the layer of track 2 of movie 1

-- get visual characteristic of track (is it visible)--

get the visual characteristic of track 2 of first movie

-- get audio characteristic of track (is it audible)--

get the audio characteristic of track 2 of first movie

-- if audio track, get balance

if audio characteristic of track 2 of movie 1 is true then get

the volume of track 2 of movie 1

-- set start time of track --

set start time of track 1 of movie 1 to 600

-- get track kind --

get track kind of track 2 of movie 1

-- get track duration (as seconds if time scale is 600)

set x to duration of track 2 of movie 1

set result to x / (time scale of movie 1)

Note that if you use (time scale of movie 1), then this becomes the generalized expression for time in seconds.

Inside Macintosh: QuickTime Reference