TC-CD (Timecode Countdown)

English | 日本語

TC-CD is a web app that follows timecode and counts down to each cue.

• Countdown timer (main use): shows when to trigger gear that cannot receive timecode, so you can run it by hand on time.
• Simple show controller (extra): sends a MIDI Note as each cue fires. MIDI Notes are the only output.

It runs in the browser on a PC. There is nothing to install, and once you have opened it, it works without an internet connection.

Open the app: https://hugesesame.github.io/timecode-countdown/ (Chrome or Edge on a PC)

Beta. TC-CD is still being tested and has not been used on a real show. MTC, LTC and MIDI output have been checked only with a few software sources. Test it with your own gear before relying on it.

What it does

• Countdown to the next cue. The color changes from yellow to orange to red as GO approaches, and flashes green at GO. The frame also lights up 3, 2 and 1 seconds before each cue, at the same moments as the click, whether or not the click is on.
• Lane: a bar under the countdown where cue markers travel toward the GO line at a steady speed, so you can see cues that follow closely.
• Cue List with pages. Each cue has a number, trigger time, name and info. Pages keep running while they are in the background.
• Timecode sources
  • Gen: a built-in generator, for programming and rehearsal. It can be started and stopped with MIDI notes
  • MTC: MIDI Timecode from a MIDI input
  • LTC: timecode decoded from an audio input
  • Clock: the time of day on the PC, for cues that run at a set time
• MIDI Note output when a cue fires, with channel, note and velocity per cue.
• Click: a click at 3, 2 and 1 seconds before a cue, and a higher tone at GO.
• Display window for a second screen, showing only the next cue, the countdown and the lane.
• Program / Show modes. Show mode enlarges the display and locks editing.
• Show files: the show is saved in the browser as you work, and can be exported to and imported from a JSON file.
• Cue sheet: print all pages as a table, or save it as a PDF, to keep a paper copy at the show.

Frame rates: 24, 25, 29.97 drop-frame and 30 fps.

Requirements

• A PC with Chrome or Edge. The app uses the Web MIDI API, and choosing the audio output for the click also needs these browsers.
• The layout is made for PC screens. Phones and tablets are not supported.

Getting started

1. On a PC, open https://hugesesame.github.io/timecode-countdown/ in Chrome or Edge.
2. That is all. There is nothing to install and no account to make.

Add a bookmark so you can open it again later.

What the browser asks you

The browser asks for permission the first time you use some features. Choose Allow each time. If you choose Block by mistake, click the icon at the left of the address bar and change the setting there.

When	What the browser asks	Why
You press Enable under MIDI	To control MIDI devices	To receive MTC and send MIDI Notes
You choose LTC as the source	To use the microphone	To read timecode from the audio input. Nothing is recorded
You press Display	To allow pop-ups (only if the window was blocked)	To open the display window

The click needs one more step: the browser does not let a page make sound until you have clicked somewhere on it. If the Click button shows ⚠ Click, click the button or anywhere on the page.

Where your show is kept

• Your show is saved as you work, in the browser on that PC. There is no Save button.
• It is not sent anywhere. A different PC, or a different browser on the same PC, does not have it.
• Clearing the browser's site data removes it.
• Press Export to save the show as a file. Do this to keep a backup, and to move the show to another PC with Import.
• Press Print to print the cue sheet of all pages, or to save it as a PDF from the print dialog. It is a good backup in case the PC stops during a show.

Without an internet connection

• Once the app is open, it keeps working if the connection drops. Timecode, MIDI, the click and the display window do not use the internet.
• The app also keeps a copy of itself in the browser. When the bottom of the side panel shows Offline ready (in Program mode), you can reload or reopen the page on that PC without a connection.
• So open the app once where you have a connection, and check for Offline ready, before you take the PC to a place without one.
• When there is a connection, the app loads the newest version each time you open it.

Try it with the demo show

samples/demo-show.json is a sample show: three pages and 20 cues of stage effects for an imaginary concert. Open that link and press the download button at the top right of the file to save it to your PC.

1. Press Import and choose the demo-show.json you saved. This replaces the current show, so export it first if you need it.
2. Set the timecode source to Gen.
3. Press play, or click the timecode display, type 00001900 and press Enter to jump to 00:00:19:00, where three cues come close together.

Using it

1. Add cues with + Add Cue and type a trigger time. Typing 1000 gives 00:00:10:00.
2. Choose the timecode source at the top left: Gen, MTC, LTC or Clock.
3. For MTC or MIDI Note output, press Enable under MIDI and choose the ports.
4. For LTC, allow microphone access and choose the audio input and channel. Nothing is recorded.
5. Switch to Show mode for the show.

A cue fires when timecode passes its trigger time. You can also fire by hand with the GO button or the space bar: it fires the selected cue, or the next cue if none is selected.

Each cue has two switches in the list:

• On / Off turns the whole cue off. It does not fire and is left out of the countdown.
• MIDI turns off only the MIDI Note. The countdown, the lane and the click stay the same, so you can count down to something you operate by hand on other gear. The GO button and the space bar do not send the Note either.

If timecode jumps forward, the cues it jumped over do not fire. If it goes back, the cues after that position become active again.

Running cues at a time of day

Choose Clock as the source to use the PC's clock as the timecode. At half past seven in the evening the timecode reads 19:30:00:00, so a cue with that trigger time fires at 19:30.

• Use it for things that are tied to the clock, such as doors, announcements and the curfew. For cues that follow the performance, timecode or the GO button is safer, because the start of a show often moves.
• If everything on a page moves by the same amount, change the page's offset. An offset of 00:10:00:00 makes every cue on that page ten minutes later.
• Cues whose time has already passed when you open the app do not fire.
• The app is only as accurate as the PC's clock. Leave the PC set to adjust its time automatically.
• The clock cannot be stopped, so play, stop and locate are turned off.
• At midnight the time returns to 00:00:00, and all cues become active again for the new day. A countdown does not run across midnight.

Controlling Gen with MIDI notes

You can start and stop Gen from a MIDI keyboard, a pad or a foot switch.

1. Press Enable under MIDI and choose the device under MIDI In.
2. Under Gen remote, press Learn next to Play, then play the note you want to use. Do the same for Stop and Rewind.
3. Press × to remove a note.

Play starts from the current position, Stop stops there, and Rewind returns to 00:00:00:00. The notes work only while the source is Gen. They are saved in the browser on that PC, not in the show file.

Countdown

• Click the countdown number to switch between whole seconds and tenths of a second. Whole seconds are rounded up, so the moment the number reaches 0 is GO. The display window follows the same setting.
• The seconds at which the color changes are set under COUNTDOWN in the side panel: Standby (yellow), Warn (orange) and Final (red). The lane shows the Standby time from end to end.
• The Stby column sets a different Standby time for one cue.

Keys

Key	Action
Space	GO
↑ / ↓	Select a cue
Alt + ↑ / ↓	Move the selected cue
Enter	Edit the selected cue (Tab moves to the next field)
C	Capture the current timecode into the selected cue
F	Fullscreen
⌘Z / Ctrl+Z	Undo
Esc	Clear the selection

Pages

• Each page has its own cue list and a timecode offset, such as the start time of a song.
• TC ON / TC OFF on a page stops timecode from firing that page's cues.
• TC ON in the header does the same for all pages. The timecode display keeps running.

Display window

Press Display in the toolbar to open a second window, then move it to the second screen. Press the button at its top right, the F key, or double-click to make it fullscreen. It follows the page shown in the main window and closes when the main window closes.

Development

This part is for people who want to change the app or build it themselves. You do not need it to use the app. It needs Node.js.

npm install
npm run dev

Open the address that appears in the terminal (normally http://localhost:5173/).

Command	What it does
npm run dev	Start the dev server
npm test	Run the tests
npm run build	Type-check and build dist/index.html

npm run build puts the whole app into one file, dist/index.html. You can copy that file to any PC and open it in Chrome or Edge without a server.

The three ways to open the app behave a little differently:

	Public site	Dev server (localhost)	dist/index.html opened directly
What you need	A browser	Node.js	A browser and the file
Internet	Needed the first time	Not needed	Not needed
Choosing audio devices (LTC input, click output)	Yes	Yes	System default only
Saved show	Kept for the site	Kept for localhost	Kept apart from both

Each one keeps its saved show apart from the others. Use Export and Import to move a show between them.

Path	Contents
src/core/	Timecode math, cue firing, MTC and LTC decoding, and their tests
src/io/	Web MIDI, LTC audio input, click sound
src/ui/	Header, cue list, side panel, display window
src/app.ts	App state and actions

Built with TypeScript, Vite and Vitest. There are no runtime dependencies.

License

MIT. You are free to use, change and share TC-CD, including at work. It comes with no warranty.