Offline-online is film's workprint-and-negative discipline in digital clothing: cut on cheap proxies, conform back to camera originals at the end - and nearly every conform bug traces back to the same two culprits, a timecode that isn't unique or a name that is. The proxy half of the workflow is documented in the proxy guide and the per-NLE proxy setups (Premiere); this is the conform half - the failure modes, what each NLE actually does at relink, and the checklist that keeps the online from becoming a re-edit.
The pitfall table
| Pitfall | Symptom at conform | Prevention |
|---|---|---|
| Duplicate timecode | Relink grabs the wrong take or wrong card; a "clip conflict" list of matches with overlapping timecode | Continuous/rec-run timecode per camera, or unique reel names per card batch |
| Reel/file name collisions | Wrong media matches on name; conform keys on names when TC is absent | Unique names before the offline starts (naming conventions) |
| Third-party transcode offsets | Avid KB: proxy TC shifted from camera TC - "no clips were relinked" | One transcode tool, verified TC mapping, spot-check a clip per card |
| Missing handles | Trims and transitions impossible after conform - the online is frame-exact and brittle | Consolidate with handles (Resolve's documented default: 12 frames) |
| Mixed frame rates | Conformed timeline drifts or judders offline from the edit | One timeline rate decided at project start; explicit conform per clip |
| Nests, retimes, transitions | Conform tools map flat event lists; the odd clip lands offline or wrong | Flatten the timeline for turnover - the colorist-handoff prep rules |
Timecode: the conform's primary key
Conform engines rebuild the online from the offline's event list, and their matching key is timecode plus identity metadata. Avid's own troubleshooting guide on failed relinks states the requirement flatly: "The timecode of the offline clips in the sequence must match the timecode of the camera original master clips you are relinking to" - with clip name, tape ID, disk label, or other shared metadata as the pairing fields, and third-party transcoders that "may generate different start timecodes" named among the failure causes. The duplicate-timecode disease starts at the camera: consumer and prosumer bodies commonly restart timecode (and clip numbering) per card, so card two's first clip can share card one's TC exactly - the offline then contains multiple valid relink targets. The camera mechanics are documented - Canon's manuals, for example, describe Rec run as advancing timecode only during recording continuing from the previous file, versus Reset, which sets "00:00:00" - but the per-card default varies by body and setting, so the working rule is practitioner consensus: run continuous (rec/free-run) TC or unique reel names per card batch before the offline begins. DaVinci Resolve makes the collision visible on purpose: its manual documents Conform Lock Enabled, which pins each timeline event to its current media-pool match, and what happens when you loosen it - a "clip conflict" badge listing "every clip in the Media Pool with a matching file name or reel name and overlapping timecode." That badge is the duplicate-TC disease, listed by name.
What each NLE does at relink
Avid Media Composer is the original offline-online machine: transcode to DNxHD 36 (now named DNxHD LB) proxies for the cut - Avid's high-resolution workflows guide calls it "an acceptable quality for editing" - then "relink the high-res media for the finishing process" when the cut locks. DaVinci Resolve conforms by import - File > Import Timeline (Shift-Command-I) or Media Pool → Timelines → Import → AAF/EDL/XML/DRT/ADL/OTIO - matching file paths first, then clip names, then "a timecode match (and reel name match if this is enabled)," with the manual noting file names are "never used when conforming EDLs" (reel names carry EDLs, via the Assist-using-reel-names setting). Resolve's own checkbox example is the workflow in miniature: "Ignore file extensions when matching" exists precisely to relink ProRes proxy media back to camera raw. Premiere Pro takes a different architecture altogether - proxies are attachments, not a separate offline: the edit always references full-res media, toggling proxies changes playback only, and Adobe's proxy pages document Attach Proxies and the proxy toggle. The cost is that Premiere has no dramatic conform moment; the risk moves to keeping attachments intact across a team (which is the problem Productions and Team Projects solve at the project layer). Final Cut Pro collapses the distinction further - one library, proxies transparent, and Apple's documented rule stays the same as the FCP proxy guide records: switch playback back to optimized/original before sharing so the export is full quality.
Handles and the flat-timeline rule
Two prep rules decide whether a conform lands clean. Handles: the online needs media beyond the cut points so trims survive - Resolve's consolidate defaults to "keeping 12 frame handles," and the industry's working floor starts around ten per side (the same numbers as the colorist handoff checklist, which shares this prep with the grade). Flatness: conform tools map flat event lists one-to-one, so nests, retimes, and transitions are turned over flattened - the prep rules are identical to the color turnover because the conform underneath is the same act. And the clock matters: mixed frame rates baked into the offline become drift baked into the online - one timeline rate, decided at project start, is the mixed-frame-rate rule, with the display conventions from the timecode primer.
When the online comes back
The conform's output is a full-res timeline that nobody has actually watched at length - which is why the first online export goes back through a review round before finishing: verify sync, verify every event re-linked (no black holes), verify the grade holds on real pixels. A review link with version history keeps that pass honest - each conform attempt becomes a new version and the sign-off state is a record, and frame-accurate notes (why that matters) are the difference between "something looks off around the middle" and a fixable timestamp. The archive step after lock is the project-archive checklist - conform data and masters included.
FAQ
Why won't my offline edit relink to camera originals?
Matching failed on the conform's key. Avid's guidance lists the usual suspects: offline timecode must equal camera-original timecode; pairing needs shared metadata (clip name, tape/Reel ID); project-format-only relink settings fail on mismatched resolutions; third-party transcodes can shift start timecode. Check TC continuity and reel names before anything else.
How do I avoid duplicate timecode across camera cards?
Make timecode unique before the offline: run continuous Rec/Free-run timecode per camera, or assign unique reel names per card batch - and spot-check one clip per card after the first transcode. Resolve users can see collisions directly via the clip-conflict list under Conform Lock.
Do I need handles on conformed media?
Yes - handles are the difference between a conform you can trim and one you re-cut. Resolve's consolidation documents 12-frame handles as its default, and working practice starts around ten per side; match the facility spec if one exists.
Does Final Cut Pro need an offline-online pass at all?
Not classically - FCP keeps one library with transparent proxy media and no separate conform step, so there is no relink moment to fail. The equivalent discipline is still required at the edges: unique metadata for multicam/sync work and Apple's switch-back-to-original rule before the share goes out.
What is the difference between conforming and colorist handoff prep?
None structurally - both rebuild a flat, predictable timeline from an event list against source media with handles. The colorist handoff is a conform with a grading target attached, which is why the two checklists share their prep rules.