Timecode Reference

Non-Drop Frame (NDF) counts frames sequentially without skipping any numbers, using colon separators (HH:MM:SS:FF). At 29.97fps, NDF drifts approximately 3.6 seconds per hour from real time. Drop Frame (DF) uses semicolon separators (HH:MM:SS;FF) and skips frame numbers 00 and 01 at the start of every minute except every tenth minute. This correction keeps DF timecode synchronized with the wall clock, which is essential for broadcast where program timing must be accurate.

When color was added to the NTSC standard, the frame rate was reduced by a factor of 1/1.001 (from exactly 30fps to 30000/1001 = 29.97002997fps) to prevent interference between the color subcarrier and the audio carrier. This 0.1% slowdown is the historical reason Drop Frame timecode exists — it compensates for the accumulated drift between the fractional frame rate and wall-clock time.

LTC (Linear Timecode) per SMPTE ST 12M-1 is timecode recorded as an FM-modulated audio signal on a dedicated audio track. It can be read during playback at variable speeds, making it ideal for field recording and multi-camera synchronization with external timecode generators (like Tentacle Sync). The main limitation is that LTC cannot be read when tape is stopped, since it requires audio playback.

Jam Sync transfers the master timecode from one device to all slave devices. You connect the master TC output to each slave TC input, execute a jam (sync), then disconnect the cables. Each device continues generating its own timecode from the synced starting point. Because internal clocks drift over time (typically +/-0.5 ppm), you should re-jam all devices before each shooting session to minimize accumulated drift.

3:2 pulldown converts 24fps film content to 29.97fps video by distributing 4 film frames across 5 video frames in a 2:3:2:3 field pattern. This was essential for broadcasting film content on NTSC television. Inverse telecine (IVTC) reverses the process by detecting and removing the duplicate fields. Understanding pulldown is critical for maintaining quality when converting between film and video frame rates.

PTP (Precision Time Protocol, IEEE 1588) provides sub-microsecond timing synchronization over IP networks. SMPTE ST 2059 defines a PTP profile specifically for professional media. As broadcast facilities transition from SDI to IP-based infrastructure (SMPTE ST 2110), PTP replaces traditional Genlock (Blackburst/Tri-Level Sync) as the timing reference, enabling frame-accurate synchronization across IP-connected devices including in cloud production environments.

For 29.97fps DF, the frame number N is calculated as: N = 108000*H + 1800*M - 2*(M - floor(M/10)) + 30*S + F, where H=hours, M=minutes, S=seconds, F=frames, and floor(M/10) is integer division. This formula accounts for the 2 frames dropped every minute except every 10th minute. The total frames per day is 2,589,408. Reverse conversion uses a similar formula with correction terms for the dropped frames.

Starting at 01:00:00:00 is a broadcast convention that reserves the hour before program start for bars, tone, slate, and countdown. The second reel starts at 02:00:00:00, and so on. This leaves 00:58:30:00 through 01:00:00:00 for pre-program material. Some facilities use 00:00:00:00 for Time-of-Day mode, and certain film conventions use 10:00:00:00 as the starting point.