Type: Embed bug player

Environment

Firefox 155.0

MacOS

Chrome and Safari: rendering correctly on the same embed

Uploaded sources: 8-bit SDR only (no client-side HDR)

Behavior On the Gumlet embed (play.gumlet.io), the image is correct as long as the cursor is on the player (chrome visible). When the cursor leaves the player and the controls disappear after autohide (~1 s), the image becomes lighter: black raised, like a semi-transparent veil.

The problem affects all of our embed videos, not just one.

Example page https://www.loisplagnard.com/film-ecole-comestible .html

Embed example

Isolation test (support suggestion) With disable_player_controls=true, the bug does not disappear: it becomes constant (image always washed).

Firefox Render Config

Active controls

Correct on hover; lag after mouseleave

disable_player_controls=true

Continuously lagging

Hypothesis The media-chrome player hides inactive chrome with opacity: 0 (userinactive) rather than removing it from the rendering. On Firefox, this seems to switch to <video>a different compositing path (hardware overlay), with black lift. Not correctable from the parent page (cross-origin iframe).

Correction track

Hide inactive chrome with visibility: hidden/display: none instead of opacity: 0

Or expose noautohide/option to avoid this path on Firefox

Attachments [Capture 1: cursor on the player — correct rendering]

[Capture 2: Cursor off the player - black raised]

[Capture 3: disable_player_controls=true — washed constantly]