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

4 days ago
https://johnlian.net/posts/hdmi-cec/
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  • #Home Automation
  • #HDMI-CEC
  • #Raspberry Pi
  • HDMI-CEC is often temperamental and not fully understood, especially with different devices behaving inconsistently.
  • The author's setup includes a Samsung TV, Denon AVR-X1700H, Apple TV, consoles, and a Raspberry Pi 4 for Homebridge.
  • Apple TV handles CEC well, but consoles fail to wake the Denon receiver, requiring manual audio output toggling.
  • The author explored automation solutions like HomeKit scenes and wattage triggers but found them laggy.
  • A Raspberry Pi was used to monitor the HDMI-CEC bus and send commands to fix the Denon wake-up issue.
  • The Pi sends a System Audio Mode Request (0x70) to the Denon when consoles wake up, ensuring proper audio routing.
  • The solution involves parsing CEC traffic and reacting to Active Source (0x82) messages from playback devices.
  • The script avoids spamming the bus by using a long-lived cec-client process and only intervening when necessary.
  • The approach can be generalized to other CEC quirks by monitoring traffic and injecting missing opcodes.
  • Remaining issues include TV switching to antenna input when consoles sleep and dead inputs during automation.
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