Timecode QuickTime returns vs. Correct timecode for DF video

currentTime method of QTMovie and [[qtMovie attributeForKey:QTMovieCurrentTimeAttribute] QTTimeValue] returns QTTime value equivalent to these.

33 sec 28
34 sec 00 ( jump 1 frame)
34 sec 01
34 sec 02

However, the correct values should be these because frame drop should not happen within a minute boundary.
33 sec 28
33 sec 29 (continue)
34 sec 00
34 sec 01

It seems to me that there is no way to correct this timecode from QuickTime API, because the timecode from QuickTime API is already modified one by QuickTime. Additionally, when the timecode jumps seems to be inconsistent by observing how the timecodes are changed for about 3 minutes. So, there seems to be no way to correct the timecode for Drop Frame video, i.e. DF video.

Fortunately there were timecode tracks in video files I am supposed to handle.
So, by reading the timecode I have these correct results.

33 sec 28th frame

33 sec 29th frame

34 sec 0th frame

Then 2 frames should be dropped at every 1 minute. But the timecodes from QuickTime API are like :

59 sec 29 frame
1 min 00 sec 00 frame
1 min 00 sec 01 frame

The expected timecodes are :

59 sec 28 frame
59 sec 29 frame
1 min 00 sec 02 frame ( jumping two frame, i.e two frames were dropped. )

59 sec 29th frame

1 min 2nd frame

The sample program to print out timecodes can be downloaded here.

2 responses to this post.

  1. Posted by gino on August 4, 2012 at 12:22 PM

    the link is no available. how can download the file?
    please help me


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