4:20
SMPTE LTC Reader & Generator
$4.99 · Designed for iPad. Not verified for macOS.
Plug into the line and know in seconds: lock, rate, drop frame, direction, level, and whether the code is clean. A pocket LTC reader for the tech on the floor.
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.
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
• 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
• 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.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
Interruption handling. Phone calls, Siri and alarms take the audio hardware away, and this release makes 4:20 give it back correctly. The generator holds its position through an interruption and resumes where the clock says it should be, or stops and tells you why it stopped. The reader re-arms on its own once the input comes back.
Frame rate detection. The reader now decides 29.97 against 30, and 23.98 against 24, from accumulated evidence rather than a single measurement, and it shows nothing at all rather than guessing when the evidence does not decide. Verified against timecode generated by other manufacturers' encoders.
Also in this release: recovery after another app releases the audio session is faster, and the Do Not Disturb tip now describes what actually happens to output during a call.
The developer, Upload Studio Ltd., indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Upload Studio Ltd
- Size
- 1 MB
- Category
- Photo & Video
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - iPad
Requires iPadOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Copyright
- © 2026 Upload Studio Ltd.
