Fix HDMI-CEC weirdness with a Raspberry Pi and a $7 cable

HDMI‑CEC Reliability and Device Behavior

• Many commenters report that Apple TV is one of the few “mostly correct” CEC implementations, but even it can be over‑aggressive (stealing inputs) or randomly stop turning TVs on/off until other components are power‑cycled or remotes rebooted.
• Consoles (PS4/5, Xbox, Switch, Steam Deck) are widely described as flaky: turning on TVs but not receivers, fighting for the active input, or triggering endless input‑switch loops.
• Soundbars and some TVs often ignore power‑off or power‑on commands, leading people to disable CEC on one component or fall back to IR.
• Some receivers (Yamaha vs Marantz/Denon) are perceived as much better CEC “citizens” than others.
• A CEC limit of about three “playback/console” devices per system confuses setups with multiple consoles plus Apple TV and eARC soundbars.

CEC Bus and Technical Details

• People are surprised that the CEC line is effectively a shared bus where every port sees all traffic; explanations compare it to I²C‑like open‑drain wiring mandated across all HDMI ports.
• External USB/HDMI CEC adapters (e.g., Pulse‑Eight) are used to add CEC to PCs and GPUs that don’t expose it, though some find this clunky and overpriced.
• Tools like cec-ctl and v4l-utils are recommended to monitor and debug CEC frames.

DIY Fixes, Raspberry Pi, and Alternatives

• The Pi‑plus‑cable approach in the article is praised as clever and cheaper/safer than many smart plugs; others share similar Pi/Pi Pico projects mapping CEC commands to keyboard events, media software, or Home Assistant.
• Additional hacks include Arduino IR blasters powered from TV USB, custom HDMI dongles for Home Assistant, Chromecast control scripts, and the Amity project that sits between TV and receiver to arbitrate CEC and stop devices “fighting.”
• Some find CEC hacking fun and ultimately stable; others say it’s so flaky they turned it off entirely.

Receivers, Audio Routing, and Form Factor Frustrations

• A long subthread laments that simple setups (TV + console + bookshelf speakers) now require understanding ARC/eARC, CEC, audio extractors, and networking.
• Suggestions include: active speakers with HDMI‑ARC, tiny HDMI‑ARC/eARC audio extractors, Toslink‑to‑RCA DACs, and small class‑D or mini‑AVR boxes (Fosi, SMSL, WiiM, Sonos Amp, etc.) as alternatives to bulky receivers.
• There’s ongoing tension between audio quality, box size, aesthetics, and “spouse acceptance.”

Universal Remotes and the Bigger Picture

• Harmony remotes are repeatedly praised as the only thing that makes complex stacks usable; there’s significant anxiety about eventual server shutdown and calls for an open firmware RF remote replacement.
• One subthread argues that much of this complexity stems from DRM/HDCP and HDMI licensing rather than inherent technical necessity; a simple PC + monitor + powered speakers is held up as an interoperability baseline.