Prevent HTPC from muting sound when connected via HDMI

Issue

Media PC occasionally boots or resumes from a sleep mode with muted sound. Sometimes even when the PC is running sounds get muted if HDMI device (Denon AVR in this case) switches inputs or is powered on or off. There is no regular pattern when this happens, but it only occurs when the PC sound is transferred to the AVR via a HDMI cable.

Resolution

I traced the issue to some extent to the Windows Away Mode, however, even with it disabled (via registry option) the sound in some instances would still get muted.

One workaround would be to use optical cable instead of HDMI for sound. However, this is not ideal as HDMI provides much better support for various surround sound formats.

I resolved the issue by a small AutoIT script that runs after certain system events and un-mutes the sound if it was muted. I used _AudioEndpointVolume library.

• Download and install latest version of AutoIT.
• Download Unmute.zip and extract _AudioEndpointVolume.au3 and Unmute.au3 files into the same folder.
• Open the Unmute.au3 file and modify value of the $logFile variable (to the path where you want the log to be saved). Logging is optional and can be removed, but I find it useful for troubleshooting purposes.
• Open Task Scheduler and create a new task:
  • Actions:
    • Action: Start A program
    • Program/script:  "C:\Program Files (x86)\AutoIt3\AutoIt3.exe"
      Path to your AutoIt3 executable
    • Add arguments: "C:\_scripts_\Unmute\Unmute.au3"
      Path to your Unmute.au3 script 
  • Triggers:
    • Trigger 1 (PC boots):
      • Begin the task: At startup
    • Trigger 2 (PC resumes from sleep):
      • Begin the: On an Event
      • Log: System
      • Source: Power-Troubleshooter
      • Event ID: 1
    • Trigger 3 (PC goes into Away Mode):
      • Begin the: On an Event
      • Log: System
      • Source: Kernel-Power
      • Event ID: 59

January 2017
Windows 7 Pro 64bit