Source: https://guthlabs.ai/docs/instruments/time-lapse-interval-calculator/mechanism/

instrument mechanism / verified-clean

# Time-Lapse Interval Calculator mechanism

The inspectable method record for Time-Lapse Interval Calculator, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The two supplied arithmetic formulas are conditionally standard, but the spec is incomplete and contains exact ambiguities about units, integer shot-count handling, endpoint timing, storage estimation, and subject speed. These must be resolved before a PASS verdict.

- The interval formula is correct only when shootDuration and finalDuration use the same time unit and fps is frames per second: interval = shootDuration / (finalDuration × fps).

- totalShots = finalDuration × fps can produce a fractional result, but a camera must capture an integer number of shots; rounding behavior is unspecified.

- The endpoint convention is unspecified: using shootDuration / totalShots assumes the shooting period is divided into shot intervals, while timing the first shot at t=0 and the last shot at the end would use totalShots - 1 intervals.

- The specification lists a storage estimate output but provides no image file-size input or storage formula.

- The computes description mentions subject speed, but no subject-speed input or formula is specified.

## Units and conventions

- shootDuration and finalDuration must be expressed in the same unit, preferably seconds.

- fps means output video frames per second and must be greater than zero.

- The resulting interval is in seconds when shootDuration and finalDuration are in seconds.

- totalShots represents video frames/photos and should be an integer after an explicitly defined rounding policy.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "shootDurationSeconds": 7200,
    "finalDurationSeconds": 30,
    "fps": 30
  },
  "expected_outputs": {
    "intervalSeconds": 8,
    "totalShots": 900
  },
  "working": "totalShots = finalDuration × fps = 30 × 30 = 900 shots. interval = shootDuration ÷ totalShots = 7200 ÷ 900 = 8 seconds."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The calculator breaks or must reject an output-fps value of zero because interval calculation divides by zero. It also has an undocumented unit ambiguity and cannot calculate the requested storage estimate because no image size or storage-per-shot input is specified.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/time-lapse-interval-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/time-lapse-interval-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/time-lapse-interval-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`

- `BOUNDARY_HAZARD_CATALOG.json`