fn known_conversion(driver: &str) -> Option<ColorSignal>Expand description
What a device is known to convert RGB with when it declares nothing itself. Only a device
whose behavior is on record earns an entry: a Raspberry Pi with firmware older than August
2024 converts to full range BT.601 and writes no video_signal_type, which the driver’s
author states in the firmware tracker and a decoded chart confirms. Guessing for a device not
on this list would put a claim in the stream that nobody has checked, and a wrong declaration
colors a picture worse than an absent one.