Root cause of the "4 people → 2 speakers" Meet call: the colored-border detector
read solid camera-off avatar tiles (orange "J", magenta "G") as active speakers
for the ENTIRE call. Those whole-call phantom spans dominated backend name
attribution, collapsing every remote voice onto one name — and the giant filled
bbox also swallowed screen-share text (WERUNBTC.COM ×49) as a speaker.
Validated against 9 real fixtures (harness over the real MeetAdapter):
Detection:
- FrameSampler.thinColoredPoints: coloured counterpart of thinWhitePoints — keeps
thin border/ring/pill edges, drops solid colour fills.
- GridCallAnalyzer.isHollow: reject a highlight component whose interior is filled
(a solid tile) vs a hollow ring (a real border). Config.maxInteriorFill (0.2 default).
- MeetAdapter: detect thin BLUE edges only (hue 180–240°, measured from the
fixtures), maxInteriorFill 0.3 (real Meet rings ≈0.2–0.3, solid tiles ≈0.36).
- Result on fixtures: John Arnold/Grant Gilliam (solid tiles) now NEVER detected;
Matt Odell/Mark detected when their blue cue is present. Sparse but never wrong —
correct for a naming hint over audio diarization.
OCR name hygiene:
- isLikelyName rejects domain-like screen-share text ("WERUNBTC.COM", OCR'd ".GOM").
- cleaned() strips trailing punctuation ("Mark." → "Mark").
- TimelineBuilder.canonicalizeByFrequency folds rare OCR misspellings into a
dominant near-twin name ("Matt Odel"/"MattOdell" → "Matt Odell", "Mare" → "Mark").
Tests: hollow-ring, extended OCR filter, fuzzy-merge. 65 pass.
Cross-platform research (Grant) flagged that the colour-border cue differs by app;
checking the real brand colours against the detector found a concrete bug: the
global 0.5 saturation threshold MISSES Teams' violet ring (#6264A7 ≈ 0.41, light
variants ~0.27) entirely and Meet's lighter blue glow (#8ab4f8 ≈ 0.44). Those
adapters would have detected nothing.
- FrameSampler.saturatedPoints: add a tunable threshold + optional hue-band gate
(degrees) so a lowered threshold doesn't pick up warm video.
- GridCallAnalyzer.Config: colorSaturation / colorMinBrightness / colorHueRange,
plumbed to the colour-border path (defaults preserve prior behaviour).
- MeetAdapter sat→0.35 (catch the glow); TeamsAdapter sat→0.22 + hue 215–275°
(catch the faint violet, reject other colours); ZoomAdapter sat 0.45 + hue
40–150° (vivid green/yellow). Values are first-pass pending real-fixture
calibration; the hue gate is the main calibration lever.
Tests: Teams now detects the faint violet ring and rejects a green one; Meet/Zoom
vivid cases still pass. 27/27 XCTest.
Signal's active-speaker cue is a 3px #ffffff rounded border (saturation ≈ 0),
which the saturation-based highlight detector could never see. Per the
Signal-Desktop source review:
- FrameSampler.thinWhitePoints: grid-sample near-white pixels that sit on a
THIN structure (a non-white pixel within edgeGap on some axis) so a border/
ring counts but a solid white blob (face, bright video) does not.
- GridCallAnalyzer: combine coloured (saturated) + white (thin) highlight
pixels; exclude name-text regions so the white footer name can't be mistaken
for the border; estimate the tile UP from the name footer (nameAtBottom);
attribute each highlight pixel to exactly one tile by containment (nearest
centre as tiebreak) so a border can't bleed into an adjacent tile.
- SignalAdapter: white border on, coloured off, name-at-bottom geometry.
Synthetic 4-tile harness now isolates each speaker with no adjacent-tile bleed;
all 15 XCTest cases pass. Real-screenshot geometry calibration still pending.
Grant Gilliam