LTC Detective M

LTC Detective reads SMPTE linear timecode (SMPTE ST 12-1) from any audio input on your iPhone or iPad and displays the decoded timecode alongside detailed signal quality measurements.

Most LTC readers show you the timecode and stop there. LTC Detective also shows you what the signal itself is doing.

WHAT IT READS

— SMPTE LTC at 23.976, 24, 25, 29.97 drop-frame, 29.97 non-drop, and 30 fps
— Drop frame flag, color frame flag, BGF0/BGF1/BGF2 user bit flags
— User bits (8 hex characters)
— Forward and reverse playback, with playback speed measured against the audio sample clock

WHAT IT MEASURES

— Peak level (dBFS)
— RMS level (dBFS)
— DC offset
— Jitter (RMS, in microseconds)
— Frame error rate
— Edge quality
— Sync word validity
— Bit rate
— Parity check

These are the measurements you need to diagnose a marginal LTC feed: a tape head that needs cleaning, a cable run picking up induced noise, a sample-rate mismatch causing drift, an AC-coupled output adding DC offset, a generator drifting against house sync.

WHAT IT SHOWS

— Live waveform of the LTC signal (240 ms scrolling window)
— Input level meter with -60 to 0 dBFS scale
— Locked / no-signal / drifting / frozen status
— Capture timestamp, dropout count, uptime
— Time since last valid LTC frame

INPUTS

— Built-in iPhone microphone
— Any USB-C or Lightning audio interface that's class-compliant with iOS
— Loopback input for testing with the built-in reference LTC generator

The reference LTC generator plays a clean test signal out of the selected output channel so you can verify your input chain is working before you go to set.

NO ACCOUNTS, NO TELEMETRY, NO ADS

The app does not collect data, does not phone home, and works fully offline. There is no account to create. There is nothing to sign in to.

PLATFORM

— Requires iOS 17 or later
— Built with native AVAudioEngine and the Accelerate framework for sub-microsecond timing accuracy
— LTC decoding via libltc (LGPL, dynamically linked; license notice in the About screen)

This is version 1.0. Coming in future updates: capture logs, exportable measurement data, and an iPad landscape layout.