Quicktime File Format (2012-08-14).pdf

Media Data Atom TypesTimecode MediaTimecode Sample DescriptionThe timecode sample description contains information that defines how to interpret time code media data.This sample description is based on the standard sample description header, as described in “Sample DescriptionAtoms” (page 99).The data format field in the sample description is always set to 'tmcd'.The timecode media handler also adds some of its own fields to the sample description.ReservedA 32-bit integer that is reserved for future use. Set this field to 0.FlagsA 32-bit integer containing flags that identify some timecode characteristics. The following flags aredefined.Drop frameIndicates whether the timecode is drop frame. Set it to 1 if the timecode is drop frame. This flag’svalue is 0x0001.24 hour maxIndicates whether the timecode wraps after 24 hours. Set it to 1 if the timecode wraps. This flag’svalue is 0x0002.Negative times OKIndicates whether negative time values are allowed. Set it to 1 if the timecode supports negativevalues. This flag’s value is 0x0004.CounterIndicates whether the time value corresponds to a tape counter value. Set it to 1 if the timecodevalues are tape counter values. This flag’s value is 0x0008.Time scaleA 32-bit integer that specifies the time scale for interpreting the frame duration field.Frame durationA 32-bit integer that indicates how long each frame lasts in real time.Number of framesAn 8-bit integer that contains the number of frames per second for the timecode format. If the time is acounter, this is the number of frames for each counter tick.ReservedA 24-bit quantity that must be set to 0.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.190