Key takeaway
A skipped timecode label can be part of the defined counting convention. Establish sample coverage separately before calling the jump lost media.
Two absent labels do not establish two absent images
A postproduction reviewer sees 00:00:59;29 followed by 00:01:00;02 and reports two missing frames. That conclusion has treated timecode labels as a consecutive count of media samples. Under the particular 29.97 drop-frame convention illustrated here, those two labels are intentionally omitted.
Apple’s archived TN 2310 explains that drop-frame timecode skips numbers, not image frames. In its NTSC example, two labels are skipped at each minute boundary except every tenth minute. Preserve the rate and convention with the values; the same rule must not be applied indiscriminately to every noninteger rate or to 59.94.
The owner’s decision is whether a reported gap concerns the label sequence or the retained media sequence. That distinction can correct a QC allegation without excusing an actual missing image.
Lay the labels beside consecutive frame ordinals
This hypothetical strip uses zero-origin media ordinals and the selected NTSC 29.97 drop-frame convention, with a nominal 30-frame label count. The actual source frame-duration rational remains separate metadata to retain rather than infer from a rounded display. This is an arithmetic illustration; no file or editing application was operated.
Ordinals 1799, 1800 and 1801 are consecutive. Their labels cross the first minute boundary as shown. The absent labels 00:01:00;00 and 00:01:00;01 are not missing samples in this fixture. A separate strip deliberately removes ordinal 1800; that creates a genuine sample-coverage question, even though a label-based explanation is also available for the minute transition.
| Zero-origin media ordinal | Selected timecode label | Coverage interpretation |
|---|---|---|
| 1799 | 00:00:59;29 | Present sample immediately before the boundary |
| 1800 | 00:01:00;02 | Present next sample; two labels omitted by convention |
| 1801 | 00:01:00;03 | Present next sample |
| Second strip: 1799 then 1801 | Labels alone do not restore ordinal 1800 | Investigate actual sample omission under the stated source sequence |
Recover the convention instead of guessing from punctuation
The label’s punctuation is a useful clue, but retain the actual timecode-format metadata. Apple’s note describes a format with frame-duration information, nominal frame quanta and flags, including drop-frame behavior. A copied string can lose those properties while keeping its semicolon.
Also identify the source timecode origin, the sequence or project origin, and whether a displayed frame count starts at zero or one. A shifted origin can make two otherwise valid exports appear to disagree. The worked strip states zero origin explicitly so its ordinals have an unambiguous local meaning.
When the archive only contains screenshots of labels, say that sample coverage has not been demonstrated. Do not fabricate an ordinal series from the displayed strings and then cite the derived series as independent proof that all media survived. The required evidence concerns the underlying samples and their actual source relationship.
A display change does not repair or delete media
Adobe’s After Effects documentation distinguishes time display from asset and output frame rate. Changing the display format does not change those frame rates. The page also distinguishes source timecode and project display choices. Preserve these settings when interpreting a screenshot or exported review note.
For the fictional first strip, switching to a consecutive frame-number display could make the 1799 → 1800 → 1801 sequence easier to inspect. It would not recover a frame from the second strip or establish that a source file has no corruption. A display setting changes the address shown to the reviewer, not the underlying evidence of what was retained.
The Apple source is an archived implementation note last updated in 2014; it supports the pinned convention and metadata explanation used here, not a claim about all current AVFoundation APIs. The Adobe page read on 16 October 2026 was updated 21 April 2026. Keep those source roles distinct.
Correct the QC finding at the right level
The completed finding for the first strip is: “No missing media ordinal in the shown sequence; the apparent two-label jump follows the stated drop-frame convention.” The second finding is: “Ordinal 1800 is absent from the supplied strip; investigate source sample coverage.” Neither finding claims that an entire delivery passed QC.
This gives the owner a useful next evidence request. Supply the rate rational, timecode flags, origin and actual sample-coverage basis for the disputed span. A familiar-looking timecode boundary is an explanation to test, not a general waiver for every discontinuity.