js-timecode

A TypeScript / JavaScript library for parsing and manipulating SMPTE timecodes and frame rates.

Development of this library is very test-driven to ensure accuracy of the frame and timecode calculations. If you'd like to contribute to this library, adding additional useful test cases is a great place to start!

Installation

npm install --save @spiretechnology/js-timecode

Usage Examples

Parse a timecode (drop frame)

import { Parse, Rate_29_97 } from '@spiretechnology/js-timecode';

const tc = Parse('00:01:02;23', Rate_29_97);
tc.toString(); // => 00:01:02;23
tc.frame; // => 1881

Parse a timecode (non-drop frame)

const tc = Parse('00:01:02:23', Rate_24);
tc.toString(); // => 00:01:02:23
tc.frame; // => 1511

Create a timecode from a frame count

const tc = new Timecode(1511, Rate_24, false /* non-drop frame */);
tc.toString(); // => 00:01:02:23
tc.frame; // => 1511

Algebra with timecodes and frames

let tc = Parse('00:01:02:23', Rate_24);
tc = tc.add(3);
tc.toString(); // => 00:01:03:02
tc.frame; // => 1514

Note: parsing timecodes that don't exist in drop frame

Drop frame timecodes skip the first 2 frames of each minute, unless the minute is a multiple of 10. This changes to the first 4 frames of each minute if the frame rate is 59.94.

For instance, in 29.97, the timecode 00:00:59:29 is immediately followed by 00:01:00:02. Two timecodes were dropped: 00:01:00:00 and 00:01:00:01

Those dropped timecodes don't correspond to any actual frame number, and so we need to choose how to resolve those frames. The choice we have made with this library is to round up the next valid frame. If you try to parse 00:01:00:00, the result will be rounded up to 00:01:00:02, which is the next valid frame in the sequence.

Contributing

We welcome contributions that make this library more reliable. To add test cases, fix bugs, or anything else, please submit a pull request.

Other resources

• spiretechnology/go-timecode - A Go library for parsing and manipulating SMPTE timecodes and frame rates.