LTC Check

SMPTE timecode checker

SMPTE timecode encoded as LTC is widely used across broadcast, video and show-control systems. LTC Check validates a SMPTE timecode WAV file before you deliver or rely on it.

What is SMPTE timecode?

SMPTE timecode is a standard (from the Society of Motion Picture and Television Engineers) for labelling frames of audio or video with hours, minutes, seconds and frames. When it's encoded as an audio signal for transport on a standard audio channel, it's called LTC (Linear Timecode) - the two terms are often used interchangeably in production work, and a "SMPTE WAV" typically means a WAV file containing an LTC track.

Frame rates and drop-frame mode

SMPTE/LTC timecode is tied to a specific frame rate, and getting this wrong is one of the most common sources of confusion between systems:

  • 24fps - common in film workflows.
  • 25fps - standard for PAL-derived video and much of European broadcast and live production.
  • 29.97fps - standard for NTSC-derived video; can run as drop-frame or non-drop-frame.
  • 30fps - used in some audio and broadcast contexts.

Drop-frame mode adjusts the timecode count at 29.97fps to keep it aligned with real time over long durations, by periodically skipping certain frame numbers - it does not drop any actual frames of audio or video. A file's drop-frame flag needs to match what the receiving system expects, or long-form timing will drift relative to wall-clock time.

Checking a SMPTE timecode WAV file

Before delivering or loading a SMPTE/LTC WAV file, it's worth confirming:

  • The frame rate matches what the project or receiving system expects
  • Drop-frame vs non-drop-frame mode is correct
  • The start timecode is correct
  • The file is continuous, with no missing, duplicate or jumped frames
  • There are no decode dropouts caused by low signal level, clipping or routing issues
  • The audio format and sample rate are as expected

LTC Check performs all of these checks automatically: it decodes the file, detects frame rate and drop-frame mode, reports the start and end timecode, and flags any continuity or signal problems it finds - see how LTC Check works for the full breakdown.

Who checks SMPTE timecode files

Broadcast and video engineers, video technicians and show-control programmers commonly need to verify a SMPTE/LTC WAV file before using it - whether it was generated in-house, exported from an NLE or DAW, or supplied by a third party. LTC Check is built for that verification step, running locally on macOS with no upload required.

Related reading

Buy LTC Check - £19