Differences

This shows you the differences between two versions of the page.

--- timecode [2016/06/21 00:18]
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+++ timecode [2021/06/03 19:48]
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-====== SMPTE Timecode ======
-Different film gauges and standards involve different numbers of frames in each second, and audio has no frames at all. Without a standardised reference point, there would be no clear or efficient way to communicate to start playback, for instance, at a certain point in two separate media; you would have to say things like "start the film at 250 frames in, if 35mm stock in the UK, 240 frames if in the USA, or 180 frames in, if super-8 stock, and play the audio at 10 seconds from the start of the tape, allowing for 3 seconds (or so) of pre-roll." It can work, but it's verbose and not very precise.
-The Society of Motion Picture and Television Engineers (SMPTE) developed a standard called **Timecode** or **SMPTE Timecode**, which assigns timestamps to media. For strict and accurate timecode, the media must be digital; analogue media cannot truly retain timecode, although it can have timecode "burned" into it, or it can be controlled by a digital player which may be able to assign timecode from known positions (but you lose accuracy, which is the point of timecode).
-===== Timecode Format =====
-Timecode decoded:
-<fs large>Hour : Minute : Second : Frame</fs>
-This means that a timecode of ''00:00:30:00'' indicates 30 seconds from the start of a timecode region (usually, but not always, the start of the media).
-A timecode of ''00:21:12:00'' translates to 21 minutes and 12 seconds.
-A timecode of ''00:03:14:15'' translates to 3 minutes, 14 seconds, and 15 frames.
-And so on.
-It is also, //time// being what it is, possibly to specify units less than a whole frame. The timecode ''00:00:12:12.5'' indicates 12 seconds, 12 frames, and a half of a frame. If you know how many frames are in one second, you can convert that value to milliseconds. For instance, if there are 24 frames per second, then 12.5 frames is ''.5208'' second or ''520.8'' milliseconds (because 12.5 divided by 24 frames is 0.5208, with 24 frames being a value equal to 1 second).
-==== Time Base ====
-The value of 24 frames per second is common because USA 35mm film stock played back at 24 fps happens to synchronize flawlessly with the normal playback speed of audio (that is, when someone's mouth moves on screen at 24 fps, the recording of their voice matches perfectly, and continues to match for as long as a consistent speed is maintained).
-That doesn't mean, however, that it's the only timebase you will see; British filmmakers use 25 fps instead of 24 fps, and video traditionally used 30 fps and later 29.97 fps, but eventually favoured 48 fps or 60 fps.
-There is no inherent method in SMPTE timecode to identify the timebase, except to look at when the frames turn over into seconds.
-==== Drop Frame ====
-Historically, there has also been something called **drop frame** timecode, which was used to account for the inherent mismatch between the traditional video 30 fps and the 29.97 fps of "modern" video formats: the fix was to simply drop 2 frame //counts// every minute, except on the tenth minute. The actual video frame is //not// dropped, only the numbers in the time code are dropped. It's a little like a leap year; on a leap year, you don't actually gain an extra day of life (and, likewise, you don't actually skip a day of life on a non-leap year), we just assign a new number to the 24 hour period that has accumulated in the leftover bits of our calendar.
-Drop frames are mostly phased out of necessity at this point, since most video formats can record and be edited in a variety of frame rates.
-===== When to Use Timecode =====
-Timecode is available across both video and audio. Strictly speaking, you don't need to use SMPTE timecode if you are not working to video, but pragmatically it is probably available to you if you find it useful. Many DAWs display timecode just as happily as they display traditional hour-and-minutes counters or measures-and-beats.
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