EXCEL TIMECODE CALCULATOR FULL
In a conversation where one person is talking about frequency and the other about time, it is easy to get out of sync.) Another way to look at it without having to look at reciprocals is to say that 29.97 frames/s means that 2,997 full frames are presented in 100 seconds. (Notice this reversal of relationship: larger frame rates mean smaller time intervals. seconds, which is a bit longer than 1/30 = 0.03333. Rather, it means that the time between frames is 1/29.97 seconds, or 0.03336666. We do not mean that frames are somehow sliced up like so many onions, with that extra 0.03rd of a frame being discarded every second. Many technical discussions will use Hz to describe frame rates.įirst, let us make clear how we are to interpret the idea of video being played at a fractional frame rate. Hertz was the first to generate and detect radio waves, and demonstrate that they were the same sort of thing as light, but oscillating at lower frequencies. The generic unit for "things per second" is Hertz, abbreviated Hz, and named after the German physicist Heinrich Hertz. Similarly we talked above about AC power varying at 60 cycles/s. We will always express frame rates in frames per second to indicate the connection between the word "per" and the operation of division. In particular, time durations found by subtracting drop-frame timecodes will be accurate to within one or two frames over arbitrary length intervals. The details will be discussed below, but the central idea is important: Drop-frame timecodes are defined so as to look like 30 frame per second times, and to reflect accurately the actual time elapsed. There are no 30 frame per second TVs.Ī frame-counting scheme called drop-frame has been developed that will allow users to ignore the distinction between 29.97 and 30 when interpreting timecodes. If they are cheap or out of adjustment this may vary, but not because of any deliberate intent to play at any rate other than 29.97 frames per second. In playing consumer videotapes they will use an internal clock which should be set to 29.97. If they are receiving broadcast video, they will synchronize to the broadcast signal, which will be 29.97 exactly. All NTSC televisions are designed to play at 29.97 frames per second. It is important to make clear: all NTSC video is intended for playback at 29.97 frames per second. It is my impression that a non-zero number of professionals may fall into this latter category as well. Many professionals do this as a verbal shorthand many non-professionals do not understand the difference.
EXCEL TIMECODE CALCULATOR TV
This color TV format is named after the committee that defined it: the National Television System Committee, or NTSC.Īs if to add to the confusion, many people refer to 29.97 frame per second video as being "30" frames per second. Today, all TVs in the US, Canada, Mexico, and Japan play at this rate. The solution was to nudge the picture rate down from 30 to 29.97 frames per second.
Changing the audio's format would have made all existing black & white TVs incompatible. The added color component to the broadcast TV signal could sometimes interfere with the preexisting audio. With the development of color TV, however, the situation became more complicated. If that were the only timecode problem facing video producers this document would be unneccesary. The conversion between times based on 25 or 30 frames per second is relatively simple.
In Europe, the AC power oscillates at 50 cycles per second, hence their adoption of 25 frame per second video rates. The AC power available at every wall outlet alternates at a rate of 60 cycles per second, providing an easily available sync signal. When black & white TV was first introduced in the US, it played at 30 frames per second. All of these descriptions of a frame's temporal location would be mutually interconvertible and their meanings unambiguous and intuitively simple.ġ08,000 frames = 1 hour + 0 minutes + 0 seconds + 0 frames = 3600 seconds. Each frame count could likewise be translated into a (possibly fractional) time in seconds. Each frame count could be translated into a unique timecode format of hours, minutes, seconds, and frames. Associated with each frame of video would be a unique frame count, starting with zero. In an ideal world, all video would play back at a uniform round-number frame rate, for example 30 frames per second. This document is a step to at least developing a common vocabulary with which to have discussions. The subject of timecodes and their use in video has occasioned much confusion. Time Codes Time Codes: The Amazing Truth HISTORY
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