RecordVirtual without a "modes" property makes Mutter derive the virtual monitor's refresh
from the PipeWire stream framerate and default to 60 Hz — so a 240 Hz client mode rendered
at 60 (the encoder just padded to 240 with duplicate frames). Pass an explicit "modes" entry
(size + refresh-rate + is-preferred) so Mutter creates the virtual monitor at the client's
exact WxH@Hz. Mutter >= 47; older Mutter ignores the unknown key (60 Hz fallback, no regression).
Confirmed first via raw D-Bus on the box, then validated end-to-end: the virtual output
Meta-0 reports 1920x1080@240.00 and the host encodes 480 *immediate* (real, not paced)
frames per 2 s.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
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