How a lab runs QC
An operator watches the program in real time on a calibrated monitor with headphones or a calibrated speaker setup, while software checks the file for things eyes miss: video levels outside the legal range, audio loudness against the delivery spec, dropped frames, and metadata that doesn't match the file name. Each fault gets a timecode, a description, and a grade. Labs use their own scales, but most boil down to three levels. A minor note is something the distributor will probably accept, a moderate fault should be fixed, and a severe fault fails the file.
Sample lines from a report
A report for a 96-minute feature master might include:
| TC in | Type | Description | Grade |
|---|---|---|---|
| 00:04:12:03 | Video | Dead pixel, upper right, 3 frames | Minor |
| 00:31:40:18 | Audio | Dialogue drop, 6 frames, center channel | Severe |
| 00:52:07:00 | Video | Flash frame at edit | Moderate |
| 01:10:22:14 | Caption | Subtitle on screen 2 seconds after line ends | Moderate |
| 01:36:02:00 | Program | Tail slate missing, black runs 4 seconds short | Minor |
One severe fault is enough to fail the whole file. The flash frame at 00:52:07:00 is typical of a conform problem: a single frame from the adjacent shot slipped in when the online was rebuilt from the EDL.
Fixes and who handles them
Picture faults go back to the online editor or colorist. A dead pixel may need a paint fix from VFX. Audio drops go back to the re-recording mixer, and caption timing goes to the captioning vendor. Each fix creates a new version, so a post-production supervisor logs which report version relates to which file. Sending the lab a file that fixed four items but broke a fifth is common enough that labs often re-check the full program rather than only the flagged timecodes.
Common misunderstandings
Filmmakers sometimes treat QC notes as creative criticism. They aren't. A lab can flag intentional grain, a deliberately clipped highlight, or a crushed night exterior as a fault. When the choice is intentional, the producer writes a waiver or a creative intent note, and most distributors accept that for minor and moderate items if the director of photography and colorist sign off. Get that note written during color grading, before the first QC, so no one argues later.
How QC connects to delivery
QC sits at the end of the deliverables process. Every master file gets its own report: the feature, the textless version, the M&E tracks, and the DCP. Budget for at least one re-QC in the post budget of your film budget.