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Timecode media allows QuickTime movies to store additional timing information that is not created by or for QuickTime. This additional timing information is typically derived from the original source material for example, SMPTE timecode or audio sample rate. In essence, you can think of a timecode media as providing a link between QuickTime–specific timing information and the original timing information from the source material.

The TimeCodeDescription QuickTime structure contains control information that allows QuickTime to interpret the samples. This includes the timecode format information. The actual sample data contains a frame number that identifies one or more content frames that use this timecode. This value identifies the first frame in the group of frames that use this timecode. In the case of a movie made from source material that contains no edits, you would only need one sample. When the source material contains edits, you typically need one sample for each edit, so that QuickTime can resynchronize the timecode information with the movie. Those samples contain the frame numbers of the frames that begin each new group of frames.

The QTPlgTimeCodeDesc class provides you with properties and methods that let you whether access or create new instances of such a QuickTime description structure.







The QTPlgTimeCodeDesc class constructors are called when you create a new instance of the class, while the ˜QTPlgTimeCodeDesc class destructor, is called automatically when the class is no more in use. Also, you can invoke the class destructor by setting the instance of the class to nil.
Once a new class instance is returned, it is good practice to check the class property to be sure that the new object can be used. See the validity requirements for more details.

The class provides you with the following initializer methods:
()
This is the default constructor. Use this constructor to create a completely new data descriptor container in memory. The class property is set to false
(other as QTPlgTimeCodeDesc)
This is the copy constructor. The properties of the object to be copied will be used to initialize the new class instance properties

returns the handle to the timecode description structure in use. useful for toolbox programmers (use with care: you could invalidate the handle causing unpredictable results (probably an application crash))
defines the time scale for interpreting the class property. The value of this property indicates the number of time units per second
specifies how long each frame lasts, in the units defined by the class property
indicates the number of frames stored per second. In the case of timecodes that are interpreted as counters (see the class property), this value indicates the number of frames stored per timer "tick"
specifies if does the timecode drop frames occasionally to stay in synchronization. Some timecodes run at other than a whole number of frames per second. For example, NTSC video runs at 29.97 frames per second. In order to resynchronize between the timecode rate and a 30 frames–per–second playback rate, the timecode drops a frame at a predictable time, in much the same way that leap years keep the calendar synchronized
specifies if the timecode values return to 0 at 24 hours
indicates if the timecode supports negative time values
indicates if the timecode has to be interpreted as a simple counter, rather than as a time value. This allows the timecode to contain either time information or counter (such as a tape counter) information
controls the display of timecode information. If this property is set to true, the timecode information is displayed when the movie is played. The timecode track must be enabled in order for the timecode information to be displayed
specifies the text characteristics that apply to timecode information displayed in a movie. Not all of the class properties are of interest for this class; the following properties will be set or get:
specifies the source information for the timecode in use