Duration, frames and timecode
Turn a duration into a frame count, and read a timecode — at 24, 25, 30 or 50 frames per second.
Why any of this is complicated at all
Because of a decision taken in 1953. Color was added to an existing 30 fps black-and-white signal, and to stop the color subcarrier beating against the sound the frame rate was nudged down by a factor of 1000/1001. Thirty became 29.97. Twenty-four became 23.976.
Seventy years later, every editor still pays for it. A timecode counter that ticks thirty numbers a second, against a picture that runs 29.97 frames a second, gains 3.6 seconds every hour. Drop frame is the patch: skip two numbers a minute, except every tenth minute, and the counter tracks the clock again.
The frames themselves are never touched. If someone tells you drop frame loses picture, they have it backwards.
Two clocks, and you should know which one you are reading
A timecode is a label, written at the nominal rate. A duration is a measurement, frames divided by the true rate. At 25 or 30 fps the two coincide and nobody thinks about it. At 29.97 non-drop they do not — and the gap only shows up when a broadcaster measures your delivery against the clock.
So this tool always shows both, and says which case you are in.
Frequently asked
What does drop frame actually drop?
A number, never a frame. At 29.97 fps, one second of timecode counts thirty numbers while only 29.97 frames go by: the counter would gain 3.6 seconds every hour. Drop frame fixes the numbering — it skips numbers ;00 and ;01 at the start of every minute except every tenth — so the counter keeps clock time. Nothing is removed from your picture. This is the single most misunderstood thing in post-production.
So when do I use drop frame?
When someone needs the timecode to be the clock: broadcast slots, live inserts, anything measured against airtime. When you are only cutting, non-drop is simpler and every frame number exists.
Why is 23.976 not 24?
Because of color television. When color was added to a 30 fps black-and-white signal in the 1950s, the frame rate was nudged by a factor of 1000/1001 to stop the color subcarrier beating against the sound. Every rate that ends in .97 or .976 still carries that 1953 decision — and it is why timecode drifts at all.
The tool shows two different times. Which is right?
Both, and that is the point. The timecode is a label written at the nominal rate. The real time is the frame count divided by the true rate. At 25 or 30 fps they are identical. At 29.97 non-drop they are not — and the tool tells you by how much rather than letting you discover it at delivery.
Which separator means what?
By convention a colon before the frames (00:01:00:02) means non-drop, and a semicolon (00:01:00;02) means drop frame. The tool writes it that way; when you type, either is accepted.