Timecode display & frame rate

The timecode display is the primary reference for the current playback position. It shows the exact SMPTE address being broadcast on every output protocol, in real time.

Reading the display

The large display shows SMPTE timecode in the standard HH:MM:SS:FF format:

HH — hours (00–23)
MM — minutes (00–59)
SS — seconds (00–59)
FF — frames (00 to the frame rate minus one)

The digits show dashes until playback starts, and again after you press Stop. The detected or configured frame rate is shown beside the Force FPS buttons under the digits (in TC Generator mode, under the digits). The remaining time of the current song appears just below the digits; click it to switch between remaining and elapsed time.

Supported frame rates

24 fps — film standard; frames 00–23
25 fps — PAL video standard; frames 00–24
29.97 fps Drop-Frame (DF) — NTSC broadcast; skips frame numbers 00 and 01 on certain minutes to stay aligned with wall-clock time
30 fps Non-Drop-Frame (NDF) — studio and post-production; frames 00–29; simpler math but drifts slightly relative to real-time over long durations

Drop-Frame vs Non-Drop-Frame

29.97 fps video runs slightly slower than exactly 30 fps. Over an hour, this adds up to approximately 3.6 seconds of drift between the timecode count and actual clock time. Drop-Frame timecode compensates by periodically skipping two frame numbers (not actual video frames) — frames 00 and 01 are skipped on every minute except every tenth minute.

The result: a one-hour program in 29.97 DF timecode runs from 00:00:00:00 to 00:59:59:29 and corresponds exactly to one hour of real time. Non-Drop-Frame does not apply this correction.

LTCast handles both Drop-Frame and Non-Drop-Frame correctly, including round-trip conversions between frame numbers and wall-clock time. The DF or NDF designation is embedded in the LTC signal and is shown in the frame rate indicator.

Auto-detection and Force FPS

While a song with embedded LTC plays, LTCast reads the LTC signal and identifies the frame rate automatically. The detected rate appears next to the Force FPS buttons.

If the auto-detection is incorrect — for example, because the LTC level is low or the file has an unusual encoding — use the Force FPS buttons (Auto, 24, 25, 29.97, 30) to override the detected rate. LTCast will decode all LTC using the forced rate. Force FPS is only shown in LTC Reader mode, and it is greyed out while Chase is on.

A warning message — FPS mismatch: detecting X but forcing Y — appears when Force FPS is active and differs from the auto-detected rate
Set Force FPS back to Auto to restore auto-detection

FPS mismatch warning

If the LTC signal in the audio file encodes a different frame rate than what LTCast is configured to decode, the timecode values will be wrong. The FPS mismatch warning is a reminder to check this setting before the show. Always verify the frame rate matches your receiving devices.

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