Working With Media Time
The Movie Toolbox provides functions that allow your application to work with the time parameters of a media.
You can use the
GetMediaDuration
function to determine a media's duration.
The
GetMediaTimeScale
and
SetMediaTimeScale
let you determine or establish a media's time scale.
GetMediaDuration
The
GetMediaDuration
function returns the duration of a media.
pascal TimeValue GetMediaDuration (Media theMedia);
-
theMedia
-
Specifies the media for this operation. Your application obtains this media identifier from such Movie Toolbox functions as
NewTrackMedia
and
GetTrackMedia
(described on
NewTrackMedia
and
GetTrackMedia
, respectively).
DESCRIPTION
The
GetMediaDuration
function returns a time value. This time value indicates the media's duration, and it is expressed in the time scale of the media.
ERROR CODES
|
invalidMedia
|
-2008
|
This media is corrupted or invalid
|
SetMediaTimeScale
The
SetMediaTimeScale
function allows your application to set a media's time scale.
pascal void SetMediaTimeScale (Media theMedia,
TimeScale timeScale);
-
theMedia
-
Specifies the media for this operation. Your application obtains this media identifier from such Movie Toolbox functions as
NewTrackMedia
and
GetTrackMedia
(described on
NewTrackMedia
and
GetTrackMedia
, respectively).
-
timeScale
-
Specifies the media's new time scale.
DESCRIPTION
In response to this request, the Movie Toolbox attempts to adjust the edit list of the appropriate track so that movie playback is unaffected. If you change a media's time scale by setting it to a smaller value, you may lose precision in media time values. In general, you should only increase the time scale value, and you should try to use integer multiples of the existing time scale.
SPECIAL CONSIDERATIONS
Do not use
SetMediaTimeScale
as a general rule. If you call this function with a number that is not an integer multiple, the duration of the samples vary unpredictably, and their start times tend to drift.
ERROR CODES
|
invalidMedia
|
-2008
|
This media is corrupted or invalid
|
GetMediaTimeScale
The
GetMediaTimeScale
function allows your application to determine a media's time scale.
pascal TimeScale GetMediaTimeScale (Media theMedia);
-
theMedia
-
Specifies the media for this operation. Your application obtains this media identifier from such Movie Toolbox functions as
NewTrackMedia
and
GetTrackMedia
(described on
NewTrackMedia
and
GetTrackMedia
, respectively).
DESCRIPTION
The
GetMediaTimeScale
function returns the media's time scale.
ERROR CODES
|
invalidMedia
|
-2008
|
This media is corrupted or invalid
|
© 1997 Apple Computer, Inc.Previous | Chapter Top | Chapter Contents | Next
