Within the data of the DV stream at the point of this error the frame proceeding the drop and the one following it have sequential numbering, meaning that the video was lost before the DV stream wasĮncoded. Each time the error manifested in the same manner with exactly 8 frames lost, an inconsistent sample-to-time value on the frame prior to the drop to cover the loss, and an increased loss of synchronization with the audio track. In the two hours of video captured from this particular setup the fluctuation causing error occurred 3 times. The result is that the audio falls 8 frames out of sync following the event. However the audio track is also missing 8 frames worth of audio which is not compensated for within the STTS associated with the audio track. This keeps the timecode track and video track in sync following the event, thus preventing further visual errors that would affect much more of the video image. As a result of this irregularity, the sample file now has a variable frame rate and averages 27.36 frames per second instead of 29.97.īy adjusting the sample to time duration the playback system is trying to compensate for the 8 dropped frames. This results in a loss of visual data where frame 43 is held through the time represented by the dropped frames, and then a visual stutter where the image jumps to original frame 52. In the resulting file the frame before the drop (in the example presented frame #43) is assigned a timeline duration (the STTS value) that is 9 times higher than the other frames, thus frame 43 is presented for 9 times longer than any other frame.
During this process 8 video frames were dropped.
STTS MEANING MAC
The sample file was recorded from a half inch video tape run through a time base corrector to an I/O box, then out as a DV stream, and into a Mac running Final Cut.
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