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Tip #1274: Where a QuickTime Movie Stores Timecode

Larry Jordan – LarryJordan.com

Timecode is a separate track stored inside the QuickTime movie container.

A typical timecode display.

Topic $TipTopic

We often think of a QuickTime movie as a file. But, it actually isn’t. It’s a container for multiple files – each of which can be different.

Timecode tracks, which are stored inside the QuickTime container, store external timecode information, such as SMPTE timecode. QuickTime provides a timecode media handler that interprets the data in these tracks to track each frame of video.

A movie’s timecode is stored in a timecode track. Timecode tracks contain:

  • Source identification information (this identifies the source; for example, a given videotape or digital file)
  • Timecode format information (this specifies the characteristics of the timecode and how to interpret the timecode information)
  • Frame numbers (these allow QuickTime to map from a given movie time, in terms of QuickTime time values, to its corresponding timecode value)

Apple has defined the information that is stored in the track in a manner that is independent of any specific timecode standard. The format of this information is sufficiently flexible to accommodate all known timecode standards, including SMPTE timecoding.

In essence, you can think of the timecode media handler as providing a link between the digital QuickTime-specific timing information and the original analog timing information from the source material.


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2 Comments
  1. Alan Nesbitt
    Alan Nesbitt says:

    Larry, Used LTC and VITC for 1” and Betacsm SP in those days depending on tape speed, switching between Read and Generate. Cables everywhere. Interesting to learn how QuickTime does it so quickly and efficiently. We edited on tape which was sent to Germany for transfer to Interactive Laser Disc. As every frame needed to be accessible on disc by computer the timing had to be so precise that we had to use what was called a Peter Pearse Analyser to ensure the PAL 8-field sequence was kept intact, otherwise hopping from one frame to another would lose colour integrity. Now FCP can hop about from frame to frame with timecode instantly. Wonderful, but in those days when the project to be done exactly to plan was more important than today’s time is money there was such excitement to line up and tweak a 12 second run in and watch a single frame of an object go to tape in the exact position. Now we just press “E” in FCP. Regards Alan Nesbitt.

    Reply
    • Larry Jordan
      Larry Jordan says:

      Alan:

      While I never created an interactive laser disk, I do remember the challenges of creating a dissolve using three quarter-million-dollar quad video tape machines – each the size of a bookcase.

      Sigh…. times change.

      Larry

      Reply

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