Source: https://guthlabs.ai/docs/instruments/timecode-math-calculator/implementation/

instrument implementation / implementation-contract

# Timecode Math Calculator implementation

A source-bound implementation contract for Timecode Math Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-274

**Effect**: Computation or source lookup only

## Input and validation requirements

The 29.97 DF domain contains skipped frame labels that must be rejected, and subtraction can produce a negative result whose display convention is unspecified. A calculator that blindly applies arithmetic or silently wraps negatives can return a misleading result.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "timecode_a": "01:02:03:12",
    "timecode_b": "00:00:10:12",
    "operation": "add",
    "frame_rate": 24,
    "mode": "non-drop-frame"
  },
  "expected_outputs": {
    "resulting_timecode": "01:02:14:00",
    "total_frames": 89616
  },
  "working": "At 24 fps: A = 1*3600*24 + 2*60*24 + 3*24 + 12 = 86400 + 2880 + 72 + 12 = 89364 frames. B = 0*86400 + 0*1440 + 10*24 + 12 = 252 frames. Sum = 89364 + 252 = 89616 frames. Convert back: 89616 - 86400 = 3216; 3216 - 2*1440 = 336; 336 - 14*24 = 0. Result = 01:02:14:00."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/timecode-math-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/timecode-math-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/timecode-math-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`