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e606cc83d1
A BrightSign emitted BLANK screenshots and logged "Screenshot sent". With hwz
enabled the video decodes onto a hardware plane outside the browser compositor
— BrightSign's docs say the HTML/JS layer "doesn't see the pixels" — so
drawImage(video) produces a fully TRANSPARENT image and throws nothing.
Chromium 87, which this XT245 reports, fails the same way.
Both capture paths set captured/drawn = true purely because drawMediaFit() had
not thrown. So the dashboard showed a dead screen while the panel played
perfectly, and the zone path painted a black rectangle in place of the labelled
placeholder drawZonePlaceholder() exists to guarantee ("never a transparent
hole"). Success reported, nothing done.
isMediaReadable() does not catch this. It answers "am I ALLOWED to read this"
(same-origin / CORS), which is a different question from "did any pixels
arrive".
videoFrameIsCapturable() probes a 16x16 scratch canvas before committing to a
full-size draw. ALPHA is the discriminator, not colour: a scratch canvas starts
transparent and a real decoded frame writes alpha=255 even when the frame is
pure black, so a legitimate fade-to-black still reads as captured while
"nothing arrived" does not. A tainted canvas counts as captured, because
tainting only happens once cross-origin pixels have actually been drawn.
Probing BEFORE the draw matters twice: it avoids a wasted full-size drawImage on
every frame of a 1fps stream, and in the zone path it stops a black rectangle
being painted underneath the placeholder.
When a video is on screen but unreadable the status card now says so, because
that card is also what shows for "no content" — without the line an operator
would reasonably conclude the screen was blank.
Not gated on BrightSign: the same silent failure exists for any stalled decoder
or engine that declines to hand back frames.
10 tests, 964 pass.
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| .. | ||
| config | ||
| db | ||
| lib | ||
| middleware | ||
| player | ||
| routes | ||
| scripts | ||
| services | ||
| test | ||
| ws | ||
| .gitignore | ||
| config.js | ||
| package-lock.json | ||
| package.json | ||
| server.js | ||
| smoke-ui.js | ||
| version.js | ||