Video Bitrate / File Size Calculator

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Audio, Music, Photography & Color

Tranche

tranche-4

Evidence ID

t4-263

Ledger rows

1

No ledger note is attached.

Review findings

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.

Formula and scope findings

• 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.

Unit assumptions

• 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.

Boundary hardening

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.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "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"
}

Related workflows

Sources and evidence

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

• VERIFIED_LEDGER.json · VERIFIED_CLEAN
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json