TimecodeTool

TimecodeTool is a simple CLI tool that does a handful of handy functions:

• Validate input timecode
• Calculate times spanning two timecodes in playback time, framecounts, and more.
• Timecode calculator where you can add timecodes or frames together.

Installation

Use as library

go get github.com/marcrleonard/TimecodeTool@latest

Download binaries

Download the latest from the releases page.

Build from source

git clone https://github.com/marcrleonard/TimecodeTool.git
cd TimecodeTool 
make build

CLI Usage

Validate

Validates a timecode and returns information about the frame.

TimecodeTool validate "00:07:00;00" --fps=29.97

Span

Calculate the duration between two timecodes.

TimecodeTool span "01:00:00:00" "01:01:00:00" --fps=23.98

Important: See Inclusive vs Exclusive Spans below for details on the -e flag.

Calculate

Perform arithmetic operations on timecodes and frame numbers.

TimecodeTool calculate "01:00:00:00" + "00:00:01:00" + 23 - "00:00:00:10" --fps=23.98

JSON Schema outputs

Get JSON schema definitions for the output formats.

TimecodeTool schema validate
TimecodeTool schema span
TimecodeTool schema calculate

Inclusive vs Exclusive Spans

IMPORTANT: Understanding inclusive vs exclusive behavior is critical for getting expected results.

Default Behavior (Inclusive)

By default, TimecodeTool treats spans as INCLUSIVE of both endpoints. This means both the start and end timecodes are included in the calculation.

Example at 24fps:

$ TimecodeTool span "00:00:00:00" "00:00:01:00" --fps 24

Length (Frames):      25        # Includes frames 0, 1, 2, ..., 24
Length (Seconds):     1.04      # 25 frames / 24fps = 1.041666...
Length (Timecode):    00:00:01:01  # Represents 25 frames

This might be surprising! A span from 00:00:00:00 to 00:00:01:00 gives you 25 frames, not 24.

Using the -e Flag (Exclusive - Industry Standard)

The -e or --exclude-last-timecode flag makes the end timecode exclusive, which matches the behavior of most video editing software (Adobe Premiere, Final Cut Pro, DaVinci Resolve, etc.).

Example at 24fps:

$ TimecodeTool span "00:00:00:00" "00:00:01:00" --fps 24 -e

Length (Frames):      24        # Includes frames 0-23, excludes frame 24
Length (Seconds):     1.00      # 24 frames / 24fps = exactly 1.0
Length (Timecode):    00:00:01:00  # Represents 24 frames (1 second)

With the -e flag, you get the expected result: exactly 1 second = 24 frames.

When to Use -e

Use -e when:

• You want spans to match industry-standard video editing software
• You think of timecodes as "up to but not including" the end point
• You want intuitive results (e.g., 1 second = 24 frames at 24fps)

Don't use -e when:

• You specifically need inclusive behavior
• You're working with existing scripts that depend on inclusive behavior
• You want to include both exact endpoints in the calculation

Visual Example

At 24fps, frames are numbered 0, 1, 2, 3, ..., 23, 24, ...

Without -e (inclusive):

Span: "00:00:00:00" to "00:00:01:00"
      [0] [1] [2] ... [23] [24]
       ^                    ^
     start                 end

Result: 25 frames (both endpoints included)

With -e (exclusive):

Span: "00:00:00:00" to "00:00:01:00"
      [0] [1] [2] ... [23] | [24]
       ^                 ^    ^
     start              end   excluded

Result: 24 frames (end excluded, like a half-open interval [start, end))

Calculate Command with -e

The -e flag also affects the calculate command when using timecode strings (not frame numbers):

Without -e:

$ TimecodeTool calculate "01:00:00:00" + "00:00:01:00" --fps 24
# Adds 24 frames (the frame index of 00:00:01:00)

With -e:

$ TimecodeTool calculate "01:00:00:00" + "00:00:01:00" --fps 24 -e
# Adds 23 frames (00:00:01:00 minus one frame)

Note: Frame numbers (like + 24) are unaffected by the -e flag.

Contributing

Pull Requests

All dev is done through pull rests on main. They cannot be merged unless they pass the status checks.

Builds

Builds will only occur if the status check on main completes with a version bump. You can still merge into main without a version bump, but a build may not occur if it is not bumped.

Todo

• Within validate
  • include frame index from 00:00:00:00
• Maybe introduce API in the lib to do NewTimecode and attempt to fix a broken timecode (divmod)
• Introduce an API to convert timecodes between different frame rates