Two regressions slipped through INC1-3:
INC4a -- BLACK BAND behind every detail-page carousel
Pre-existing 2026-05-08 home-page rule painted .emby-scroller {bg:#000
!important} UNSCOPED. Hits every carousel inside .itemDetailPage incl
admin-only More from Season N, More Like This. INC1-3 transparent-scope
list missed .emby-scroller / .verticalSection / .padded-top-focusscale.
Fixed by extending scope.
INC4b -- VIDEO 'BLACK SCREEN' on play
Not actually black-screen. CPU-only nullstone cannot sustain real-time
4K HEVC HDR tonemap+x264 transcode -- 0.5x realtime, ffmpeg takes ~6s
per 3s segment. With user resume seeks adding restart overhead, total
wait ~18s before browser readyState rises. User saw black, gave up.
Fix: disable EnableTonemapping (R&M fake HDR per doc 21) + cap
RemoteClientBitrateLimit=20Mbps on every user (1080p target, no 4K
scale). Headless v2 test confirms HEVC + AV1 episodes now hit
readyState=3/4 within wait window; 4K HDR R&M still slow (heaviest).
INC4 testing methodology audit -- bin/headless-test-v2.py
v1 only logged in as guest and never clicked Play. v2 runs both admin
and guest, walks 3 codec-tagged items per role (HEVC/AV1/H.264),
clicks Play, captures <video> state, sweeps DOM for opaque bgs over
backdrop layer. False positives: off-viewport #reactRoot + collapsed
.mainDrawer (negative coords). Allowlist refinement TODO.
Open: 4K HDR sources still slow even post-fix. Real fix path = pre-
transcode masters to 1080p H.264 SDR via separate batch, OR migrate to
10.11.8 with vaapi/qsv driver fixed.
