Texas Instruments DM365, User Manual

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A-1
Appendix A
Time-Stamp Insertion
The DM365/DM368 H.264 Encoder supports insertion of frame time-stamp
through the Supplemental Enhancement Information (SEI) Picture Timing
message. The time-stamp is useful for audio-synchronization and
determining the exact timing for display of frames. The parameters coded
in the SEI Picture Timing Message are also useful for testing HRD
compliance.
The application should take proper care while setting the parameters for
time-stamp and the actual time-stamp for each frame. Ideally, the time-
stamp can be set based on the frame-rate. This simplifies the process of
generating time-stamps. However, the application is free to use any
method of time-stamp generation.
Time-stamp based on frame-rate can be generated as follows.
Let f be the frame-rate of the sequence. Assuming a constant frame-rate
sequence, set
TimeScale = k * f
NumUnitsinTicks = n
where k is an integer such that (k * f) and (k/n) are
integers
units_per_frame = k/n
For the first frame, set the
TimeStamp
parameter in
inArgs
structure to 0.
For the subsequent frames, increment the
TimeStamp
by
units_per_frame
Example 1.
f = 30.
Let k = 2
TimeScale = 2 * 30 = 60
NumUnitInTicks = 1
units_per_frame = 2
TimeStamp = 0, 2, 4, 6, 8…