Source: https://guthlabs.ai/docs/instruments/video-bitrate-file-size-calculator/implementation/

instrument implementation / implementation-contract

# Video Bitrate / File Size Calculator implementation

A source-bound implementation contract for Video Bitrate / File Size 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**: t4-263

**Effect**: Computation or source lookup only

## Input and validation requirements

A zero-duration inverse calculation produces an undefined result and must be rejected. The specification also leaves audio-bitrate inclusion and decimal-versus-binary size units ambiguous, which can produce materially different displayed results.

## 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": {
    "duration_s": 600,
    "bitrate_mbps": 8
  },
  "expected_outputs": {
    "file_size_MB": 600
  },
  "working": "size = bitrate × duration ÷ 8\n= 8 Mbps × 600 s ÷ 8\n= 4,800 ÷ 8\n= 600 MB"
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/video-bitrate-file-size-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/video-bitrate-file-size-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/video-bitrate-file-size-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`