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About this tool
Convert SMPTE HH:MM:SS:FF timecode to seconds and frames and back, with correct drop-frame and 1.001 pulldown handling.
SMPTE timecode counts frames, not seconds, so converting HH:MM:SS:FF to a duration means turning the label into a frame number and dividing by the true frame rate. This converter does both directions at 23.976 through 60 fps, applies the SMPTE ST 12-1 drop-frame rule (skip two frame numbers at the start of every minute except every tenth, four at 59.94), and divides by the exact 1000/1001 NTSC rate rather than the rounded one.
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Illegal labels such as 00:01:00;00 are rejected rather than quietly converted.
Uses 30000/1001 and 24000/1001, not 29.97 and 23.98, so long durations do not accumulate error.
Every result shows the sequential frame index, which is what conform tools actually match on.
Turn the timecode into a total frame count, then divide by the real frame rate. At 25 fps, 00:01:30:12 is (90 × 25) + 12 = 2262 frames, and 2262 ÷ 25 = 90.48 seconds. At NTSC rates divide by 30000/1001 rather than 30.
Both count exactly the same frames; only the labelling differs. Drop-frame skips frame numbers 00 and 01 at the start of every minute except every tenth minute, which keeps the label within about 2 frames of the wall clock. Non-drop 29.97 labels every frame, so one hour of timecode takes 3603.6 real seconds — 3.6 seconds long.
No. It drops frame numbers, never pictures. A drop-frame and a non-drop version of the same clip contain an identical number of frames; the drop-frame version simply never uses certain labels, which is why 00:01:00;00 does not exist while 00:01:00;02 does.
When colour was added to NTSC the frame rate was pulled down by a factor of 1000/1001 to keep the colour subcarrier from beating against the audio carrier. The exact rate is 30000/1001 ≈ 29.970030 fps, and the same 1.001 factor gives 23.976 and 59.94.
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