DF/NDF checker and converter

One frame position. Two counting modes.

Choose the source counting mode explicitly. The checker counts from frame zero, converts the resulting index and shows the neighbouring labels in the source mode.

Preserve the frame index when converting.

At 29.97 NDF, 01:00:00:00 has index 108,000. Relabelling that same index as DF gives 01:00:03;18. No pictures are removed and no playback-rate change is made. This is a counting-mode conversion, not a media standards conversion.

Typing a similar clock face under another mode has a different meaning. At 29.97 DF, 01:00:00;00 has index 107,892 and plays for 3599.9964 seconds from zero. Its NDF equivalent is 00:59:56:12. Treating the two one-hour labels as interchangeable shifts the position by 108 frames.

Skipped DF labels are invalid inputs.

At 29.97 DF, 00:00:59;29 advances directly to 00:01:00;02. At 59.94 DF in this tool’s full-rate 60-count display, 00:00:59;59 advances to 00:01:00;04. Labels are skipped at each minute except every tenth minute; picture frames remain consecutive.

The checker rejects skipped labels instead of silently correcting them. Minutes and seconds must be 00–59, and the frame field must be 00–29 or 00–59 for the selected rate. Source positions cannot be negative or have hours above 23. The selected source mode is authoritative: DF accepts colon input and returns a canonical semicolon; NDF rejects semicolon input.

Previous and next refer to adjacent picture frames, not adjacent written numbers. At index zero there is no previous position. The 59.94 display is a stated counting representation; confirm the representation used by the receiving system.

Do not infer a date from the result.

A source NDF position near the end of its timecode day can convert to a DF label above 24 hours. The checker retains that index and does not silently wrap it. Those extended results are not accepted as new source inputs here.

Actual systems can apply different day-wrap policies. Neither output establishes a recording’s date or time-of-day origin. Read the drop-frame guide, timecode mathematics reference and broadcast timing standards reference, or use the timecode calculator for arithmetic.