After Effects' Interpret Footage has Start Timecode: Use Source File
Timecode, or Override Start, which changes the timecode the footage
shows and leaves its frames alone. The Start Frame field that trimmed or
padded a sequence's head isn't in After Effects, so it is replaced.
Footage.start_timecode (Override Start, in frames at the footage's
rate; None = Use Source, 0 as file timecode isn't read) relabels source
time: the Footage panel's current time and footage.info's `timecode`
count from it. file.interpretFootage takes `overrideStart` and
`startTimecode` (timecode, read at the footage's rate after any frame
rate change, or a frame number, 0 to 1e9). It applies to every footage
with time, not only sequences, and Reload keeps it. A sequence's frames
always run from its first file's number to its last.
Test: start_timecode_only_relabels_source_time (project),
interpret_footage_start_timecode_relabels_source_time (engine: the
reply, the Footage panel's timecode, frame numbers, Use Source, the
footage's rate, bad values, undo), Reload keeps it, and the Interpret
Footage fields in ui_drag_drop.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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