Time Code Sample Description
The time code 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 Table Atoms"
.
The Data format field in the sample description is always set to
'tmcd'
.
The time code media handler also adds some of its own fields to the sample description.
-
Reserved
-
A 32-bit integer that is reserved for future use. Set this field to 0.
-
Flags
-
A 32-bit integer containing flags that identify some time code characteristics. The following flags are defined.
-
Drop frame
-
Indicates whether the time code is drop frame. Set it to 1 if the time code is drop frame. This flag's value is 0x0001.
-
24 hour max
-
Indicates whether the time code wraps after 24 hours. Set it to 1 if the time code wraps. This flag's value is 0x0002.
-
Negative times OK
-
Indicates whether negative time values are allowed. Set it to 1 if the time code supports negative values. This flag's value is 0x0004.
-
Counter
-
Indicates whether the time value corresponds to a tape counter value. Set it to 1 if the time code values are tape counter values. This flag's value is 0x0008.
-
Time scale
-
A 32-bit integer that specifies the time scale for interpreting the Frame duration field.
-
Frame duration
-
A 32-bit integer that indicates how long each frame lasts in real time.
-
Number of frames
-
An 8-bit integer that contains the number of frames per second for the time code format. If the time is a counter, this is the number of frames for each counter tick.
-
Reserved
-
A 24-bit quantity that must be set to 0.
-
Source reference
-
A user data atom containing information about the source video tape. The only currently used user data list entry is the
'name'
field. This entry contains an international text item specifying the name of the source tape.
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