Video Bitrate / File Size Calculator mechanism

Model scope

The arithmetic formulas are standard under the stated decimal-unit assumptions, but the spec needs review because it ambiguously defines audio bitrate handling and file-size units. The honest-label wording is directionally appropriate but should also disclose container and metadata overhead.

• The size formula is correct only when bitrate is the total stream bitrate in decimal Mbps and the result is decimal megabytes (MB).
• The specification lists an audio track bitrate but does not define whether the supplied bitrate already includes audio or whether audio bitrate must be added to video bitrate.
• The inverse formula is correct for required total bitrate, but it does not state whether the result is video-only bitrate or total video-plus-audio bitrate.
• The formulas omit container overhead, headers, metadata, and other non-media data; the honest label mentions codec/VBR variation but does not explicitly mention container overhead.

Units and conventions

• 1 Mbps means 1,000,000 bits per second.
• 1 MB means 1,000,000 bytes; the formulas do not produce MiB unless a conversion is applied.
• Duration is measured in seconds.
• Bitrate values are measured in Mbps.
• For vectors using separate video and audio bitrates, total bitrate is assumed to be video bitrate plus audio bitrate.
• Required bitrate assumes the target size is a decimal MB value unless explicitly converted from MiB.

Inspectable vector

One of 4 source-bound review vectors:

{
  "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"
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

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.

Other records

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