4 vs LTC Detective M

4:20 is an SMPTE LTC timecode reader and generator for iPhone and iPad. It reads timecode from a wired audio input and shows lock, frame rate, drop frame, measured rate, direction, and level. It can generate LTC at the same time, over the same connection. The reader is made for troubleshooting. When a rig will not chase, plug into the line and check the code where you stand: the rate as measured against what the source claims, drop frame or not, which direction it is running, and how hot the line is. Mislabeled rates, code that should have stopped, and low or clipping levels all show up in the first few seconds. Between cues, it works as a confidence monitor on any line you need to trust. The screen does not sleep while a mode is running, and timecode keeps going when you switch to another app. Checking a message does not stop the code. READER • Lock state and a full readout: frame rate with drop frame flag, measured rate, direction, level • Runs continuously and keeps reading through route changes and interruptions • Keeps reading in the background while you use another app • If iOS takes the audio session away, the readout dims and says so instead of holding stale numbers GENERATOR • 23.976, 24, 25, 29.97 drop frame, and 30 fps • Start from any timecode, or generate time of day • Output level control, with left, right, or both channel routing • Anchored to the system clock, so long runs hold their time • Keeps generating in the background while you use another app • Runs alongside the reader for loop-through checks • Warns before sending LTC to a speaker, Bluetooth, or AirPlay, and requires a press-and-hold to override REQUIREMENTS A wired audio connection: a class-compliant USB audio interface, or a headset-jack adapter with a line input. There is no microphone mode. This version reads and generates LTC only; MIDI timecode is not supported. PRIVACY No account, no analytics, and no network connection. Nothing leaves the device. Made for production sound, playback and show control, video engineering, DIT carts, and broadcast maintenance.

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.