SMPTE LTC

What is LTC?

Linear Time Code (LTC) encodes SMPTE timecode as a bi-phase mark encoded audio signal. It sounds like a distinctive high-pitched buzzing — if you've heard a "timecode stripe" on a tape or seen an audio waveform that looks like dense square waves, that's LTC.

Because LTC is an audio signal, it can travel through any audio path — XLR cables, 1/4" jacks, audio interfaces, mixing consoles, and even recorded to audio tracks. This makes it incredibly versatile for live events where MIDI or network connectivity isn't available.

Why Use LTC?

LTC excels in scenarios where other timecode formats can't reach:

• Long cable runs — audio cables run hundreds of meters without signal degradation, unlike MIDI's 15m limit
• Existing audio infrastructure — use the venue's installed audio snake or patchbay to route timecode
• Recording — LTC can be recorded alongside audio tracks for post-production sync
• Analog gear — any device with an audio input can receive LTC, no digital protocol support needed

macOS Audio Routing

To route LTC between applications on macOS, use a virtual audio device like BlackHole (open-source):

• Install BlackHole (2-channel is sufficient)
• In TimecodeLink, select BlackHole as the LTC audio output
• In your show control software, select BlackHole as the audio input and enable LTC chase

For hardware output (sending LTC to a physical audio connection), select your audio interface output in TimecodeLink's LTC settings.

TimecodeLink LTC Output

TimecodeLink generates a clean LTC audio signal from the current deck's timecode position. The signal follows DJ pitch adjustments — when the DJ speeds up, the LTC runs faster, keeping visual cues aligned with the music.