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FA-78456 / Broadcast timecode arithmetic / Open access

Drop-frame label increment: tenth-minute exemption · case 01

Labels are skipped at minutes 10, 20 and 30 but kept at the other minutes.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The exemption test is inverted.

THE FAILURE

The exemption test is inverted.

Unsuccessful approach: Exempting only minute zero skips labels at minutes 10 through 50.

Case contract

Given a valid drop-frame label at rate "29.97" (nominal 30, drop 2) or "59.94" (nominal 60, drop 4), return the next label: frames carry into seconds at the nominal rate, seconds into minutes, minutes into hours (wrapping at 24); on entering a new minute not divisible by 10 the first drop labels are skipped.

Why this case matters

Timecode arithmetic errors misplace edits, commercial breaks and captions against the broadcast clock.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import re
N = 1
observations = []
def solve(tc, rate):
    n=30 if rate=='29.97' else 60
    drop=2 if n==30 else 4
    h,m,s,f=map(int,re.split('[:;]',tc))
    f+=1
    if f==n:
        f=0
        s+=1
        if s==60:
            s=0
            m+=1
            if m==60:
                m=0
                h=(h+1)%24
            if m%10==0:
                f=drop
    return '%02d:%02d:%02d;%02d'%(h,m,s,f)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: tenth-minute exemption', ['00:00:59;29', '29.97'], '00:01:00;02'), ('regression variant: tenth-minute exemption', ['09:10:59;29', '29.97'], '09:11:00;02'), ('partial repair probe: tenth-minute exemption', ['23:09:59;29', '29.97'], '23:10:00;00'), ('partial repair variant: tenth-minute exemption', ['01:09:59;29', '29.97'], '01:10:00;00'), ('boundary control', ['00:01:00;02', '29.97'], '00:01:00;03'), ('normal control', ['01:01:01;02', '29.97'], '01:01:01;03'), ('normal control', ['09:19:58;05', '59.94'], '09:19:58;06'), ('normal control', ['09:19:59;58', '59.94'], '09:19:59;59')], [('regression: tenth-minute exemption', ['00:09:59;29', '29.97'], '00:10:00;00'), ('regression variant: tenth-minute exemption', ['09:00:59;29', '29.97'], '09:01:00;02'), ('partial repair probe: tenth-minute exemption', ['09:29:59;59', '59.94'], '09:30:00;00'), ('partial repair variant: tenth-minute exemption', ['23:19:59;29', '29.97'], '23:20:00;00'), ('boundary control', ['00:01:00;02', '29.97'], '00:01:00;03'), ('normal control', ['00:29:59;00', '59.94'], '00:29:59;01'), ('normal control', ['00:10:59;01', '59.94'], '00:10:59;02'), ('normal control', ['01:19:00;04', '59.94'], '01:19:00;05')], [('regression: tenth-minute exemption', ['00:00:59;59', '59.94'], '00:01:00;04'), ('regression variant: tenth-minute exemption', ['23:59:59;59', '59.94'], '00:00:00;00'), ('partial repair probe: tenth-minute exemption', ['23:29:59;59', '59.94'], '23:30:00;00'), ('partial repair variant: tenth-minute exemption', ['00:19:59;59', '59.94'], '00:20:00;00'), ('boundary control', ['00:01:00;02', '29.97'], '00:01:00;03'), ('normal control', ['00:29:58;02', '59.94'], '00:29:58;03'), ('normal control', ['00:00:01;58', '59.94'], '00:00:01;59'), ('normal control', ['23:29:01;15', '29.97'], '23:29:01;16')], [('regression: tenth-minute exemption', ['23:59:59;29', '29.97'], '00:00:00;00'), ('regression variant: tenth-minute exemption', ['23:09:59;59', '59.94'], '23:10:00;00'), ('partial repair probe: tenth-minute exemption', ['09:29:59;29', '29.97'], '09:30:00;00'), ('partial repair variant: tenth-minute exemption', ['00:29:59;29', '29.97'], '00:30:00;00'), ('boundary control', ['00:01:00;02', '29.97'], '00:01:00;03'), ('normal control', ['23:29:00;04', '59.94'], '23:29:00;05'), ('normal control', ['01:10:58;15', '29.97'], '01:10:58;16'), ('normal control', ['09:01:01;01', '29.97'], '09:01:01;02')], [('regression: tenth-minute exemption', ['09:01:59;29', '29.97'], '09:02:00;02'), ('regression variant: tenth-minute exemption', ['23:09:59;29', '29.97'], '23:10:00;00'), ('partial repair probe: tenth-minute exemption', ['01:19:59;59', '59.94'], '01:20:00;00'), ('partial repair variant: tenth-minute exemption', ['00:19:59;29', '29.97'], '00:20:00;00'), ('boundary control', ['00:01:00;02', '29.97'], '00:01:00;03'), ('normal control', ['23:10:58;03', '29.97'], '23:10:58;04'), ('normal control', ['01:19:01;05', '59.94'], '01:19:01;06'), ('normal control', ['01:09:01;58', '59.94'], '01:09:01;59')]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: tenth-minute exemption00:01:00;0000:01:00;02Failed
regression variant: tenth-minute exemption09:11:00;0009:11:00;02Failed
partial repair probe: tenth-minute exemption23:10:00;0223:10:00;00Failed
partial repair variant: tenth-minute exemption01:10:00;0201:10:00;00Failed
boundary control00:01:00;0300:01:00;03Passed
normal control01:01:01;0301:01:01;03Passed
normal control09:19:58;0609:19:58;06Passed
normal control09:19:59;5909:19:59;59Passed

SHA-256 / 8ececa7360ffdd18569d55596459bdb385fe4625df878106a1df3e45869660a2

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import re
N = 1
observations = []
def solve(tc, rate):
    n=30 if rate=='29.97' else 60
    drop=2 if n==30 else 4
    h,m,s,f=map(int,re.split('[:;]',tc))
    f+=1
    if f==n:
        f=0
        s+=1
        if s==60:
            s=0
            m+=1
            if m==60:
                m=0
                h=(h+1)%24
            if m!=0:
                f=drop
    return '%02d:%02d:%02d;%02d'%(h,m,s,f)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: tenth-minute exemption', ['00:00:59;29', '29.97'], '00:01:00;02'), ('regression variant: tenth-minute exemption', ['09:10:59;29', '29.97'], '09:11:00;02'), ('partial repair probe: tenth-minute exemption', ['23:09:59;29', '29.97'], '23:10:00;00'), ('partial repair variant: tenth-minute exemption', ['01:09:59;29', '29.97'], '01:10:00;00'), ('boundary control', ['00:01:00;02', '29.97'], '00:01:00;03'), ('normal control', ['01:01:01;02', '29.97'], '01:01:01;03'), ('normal control', ['09:19:58;05', '59.94'], '09:19:58;06'), ('normal control', ['09:19:59;58', '59.94'], '09:19:59;59')], [('regression: tenth-minute exemption', ['00:09:59;29', '29.97'], '00:10:00;00'), ('regression variant: tenth-minute exemption', ['09:00:59;29', '29.97'], '09:01:00;02'), ('partial repair probe: tenth-minute exemption', ['09:29:59;59', '59.94'], '09:30:00;00'), ('partial repair variant: tenth-minute exemption', ['23:19:59;29', '29.97'], '23:20:00;00'), ('boundary control', ['00:01:00;02', '29.97'], '00:01:00;03'), ('normal control', ['00:29:59;00', '59.94'], '00:29:59;01'), ('normal control', ['00:10:59;01', '59.94'], '00:10:59;02'), ('normal control', ['01:19:00;04', '59.94'], '01:19:00;05')], [('regression: tenth-minute exemption', ['00:00:59;59', '59.94'], '00:01:00;04'), ('regression variant: tenth-minute exemption', ['23:59:59;59', '59.94'], '00:00:00;00'), ('partial repair probe: tenth-minute exemption', ['23:29:59;59', '59.94'], '23:30:00;00'), ('partial repair variant: tenth-minute exemption', ['00:19:59;59', '59.94'], '00:20:00;00'), ('boundary control', ['00:01:00;02', '29.97'], '00:01:00;03'), ('normal control', ['00:29:58;02', '59.94'], '00:29:58;03'), ('normal control', ['00:00:01;58', '59.94'], '00:00:01;59'), ('normal control', ['23:29:01;15', '29.97'], '23:29:01;16')], [('regression: tenth-minute exemption', ['23:59:59;29', '29.97'], '00:00:00;00'), ('regression variant: tenth-minute exemption', ['23:09:59;59', '59.94'], '23:10:00;00'), ('partial repair probe: tenth-minute exemption', ['09:29:59;29', '29.97'], '09:30:00;00'), ('partial repair variant: tenth-minute exemption', ['00:29:59;29', '29.97'], '00:30:00;00'), ('boundary control', ['00:01:00;02', '29.97'], '00:01:00;03'), ('normal control', ['23:29:00;04', '59.94'], '23:29:00;05'), ('normal control', ['01:10:58;15', '29.97'], '01:10:58;16'), ('normal control', ['09:01:01;01', '29.97'], '09:01:01;02')], [('regression: tenth-minute exemption', ['09:01:59;29', '29.97'], '09:02:00;02'), ('regression variant: tenth-minute exemption', ['23:09:59;29', '29.97'], '23:10:00;00'), ('partial repair probe: tenth-minute exemption', ['01:19:59;59', '59.94'], '01:20:00;00'), ('partial repair variant: tenth-minute exemption', ['00:19:59;29', '29.97'], '00:20:00;00'), ('boundary control', ['00:01:00;02', '29.97'], '00:01:00;03'), ('normal control', ['23:10:58;03', '29.97'], '23:10:58;04'), ('normal control', ['01:19:01;05', '59.94'], '01:19:01;06'), ('normal control', ['01:09:01;58', '59.94'], '01:09:01;59')]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: tenth-minute exemption00:01:00;0200:01:00;02Passed
regression variant: tenth-minute exemption09:11:00;0209:11:00;02Passed
partial repair probe: tenth-minute exemption23:10:00;0223:10:00;00Failed
partial repair variant: tenth-minute exemption01:10:00;0201:10:00;00Failed
boundary control00:01:00;0300:01:00;03Passed
normal control01:01:01;0301:01:01;03Passed
normal control09:19:58;0609:19:58;06Passed
normal control09:19:59;5909:19:59;59Passed

SHA-256 / c4ec1f3c13498459a988b2fbec70acac0a36e02a9e077d54a3ad67e4357685d1

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

A deterministic bounded teaching model with a stipulated toy contract; it does not claim conformance to SMPTE or any broadcast standard. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:49:35.323174+00:00.

Case digest / 19e81faefe899d6d7bfde3b25bb28b8d4bbc6fe25f53b78e6979cbe91878088f