dropframe

Drop-frame timecode is a convention used in SMPTE timecode to keep timecode values aligned with wall-clock time when working with NTSC video captured at 29.97 frames per second. It is one of two common timecode modes: drop-frame (DF) and non-drop frame (NDF). DF timecode compensates for the slight difference between 29.97 and 30 frames per second, helping the displayed time match real elapsed time over long durations.

In drop-frame timecode, the clock counts frames as if at 30 fps but drops two frame numbers at the start of every minute that is not divisible by 10. Practically, this means the frame numbers 00 and 01 are omitted from those minutes in the timecode. The notation typically uses a semicolon to separate frames from seconds, written as HH:MM:SS;FF rather than HH:MM:SS:FF.

Drop-frame timecode has been widely used in broadcast and production workflows in NTSC regions where accurate timekeeping with real-time media is important for playout, logging, and synchronization. It is less common in 30p, PAL, or digital workflows, where non-drop frame timecode or alternative synchronization methods may be preferred. Many modern editing and nonlinear editing systems support both DF and NDF.

Historically, DF timecode is defined by SMPTE standards and remains a tool for compatibility with legacy tape formats and broadcast chains. Users must choose the appropriate mode to ensure timecode and reel timing remain consistent across devices and software.