The Basics of Synchronization and Time Code (3)

The Music Telegraph | Text 2019/08/20 [14:19]

The Basics of Synchronization and Time Code (3)

The Music Telegraph| 입력 : 2019/08/20 [14:19]

© Giphy



 

The Basics of Synchronization and Time Code (3)

 

 

SMPTE contains the location, or address. Address answers the question, "Where are we?". How fast we get to where we are is determined by the frame rate. Common frame rates are 30 fps (frames per second), 29.97 fps, 29.97 df (drop frame), 24 fps, and 25 fps. For audio work, 30 fps is the standard, and you (hopefully) will stripe your 2-inch and ADATs with 30 fps when dealing with a purely audio session. Note that 30 fps is simply that: in the period of one second thirty video frames will pass. However, the film standard is 24 fps: in one second of film 24 frameswill pass. Adding to the confusion, 25 fps is the standard for most of Europe, Asia, and South America. (This 25 fps standard is commonly referred to as PAL or SECAM).

 

 

NTSC 29.97 fps is the video standard for the United States. You are probably asking, how can you have .97 of a frame? Because 29.97 fps is actually 30 "frames" of video running slightly slow. It just takes a little longer to run its full 30 frames, 0.1% slow to be exact, which makes for 3.6seconds over the course of an hour. Think how funny it would look at the end of your favorite hour-long TV program if the dialogue was 3.6 seconds late compared to the picture.

 

 

▲ Introducing 29.97 drop frame.

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Remember good old 29.97 fps that ran 0.1% slow? A common problem with standard 29.97 fpsis that, over time, the counter (hours : minutes : seconds : frames) will run slow compared to the clock on the wall. The display on your video machine says it's only been an hour, yet the clock on the wall says it's been one hour and 3.6 seconds. And with broadcast TV stations (usually) running on time, they wouldn't be too happy about cutting off 3.6 seconds of a show or commercial every hour. Enter the solution: 29.97 drop frame. This format "drops" pre-determined frames so that that counter display on your video machine runs with the clock on the wall. Drop frame skips frame 0 and 1 at the beginning of every minute that is not a multiple of 10. By doing this "math", drop frame effectively removes 108 frames per hour, which gives us exactly 3.6 seconds. 

 

 

 

 

 

 

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