There have recently been a lot of threads created in regards to losing audio over HDMI connections. This has happened in conjunction with the release of Windows* 8.1, and I have a bit of information that might beneficial to some of you.
There are multiple similar issues/symptoms which I will introduce below;
1. When connected to an AV/Receiver, audio is lost when the system goes to sleep and is woken up, or if the display is not powered on before booting up, or powering the display OR AV/R off. (Reported on Gigabyte*, Intel and ASROCK* motherboards) This issue was tested in house on an Intel board, and was resolved by using the latest driver we provide on our website, and a newer BIOS. Currently we have only received information for this issue as it applies to the 8 Series motherboards (those that natively run our 4th Generation Intel® Core™ Processors). If you are still experiencing the issue with the latest driver and BIOS for your system, do check with your computer manufacturer (OEM) if they have plans to release a newer BIOS or raise the request for a BIOS update. For 4th Gen Intel® Core™ Processors, the change needed in the BIOS to address this issue needs to contain "RC 1.6.2 (v131.4 or later BIOS)". We currently DO NOT have a similar resolution for the issue as it manifests on 3rd Gen Intel® Core™ Processors, and we are still looking into it.
2. When directly connected from system to audio-enabled display and you change the audio input or turn off the display, turn off the display, or wake the system up from sleep - audio is lost. (Reported on Asus*, Gigabyte* and ASROCK* motherboards). This issue has largely been resolved by a combination of BIOS and Graphics Driver updates. Please verify that your system is running the latest of both the BIOS and Graphics Drivers.
3. No HDMI audio output regardless of AV/R connection or reboot. (Reported on Gigabyte* motherboards and Sony* laptops). This issue is still under investigation. For now we are advising users with ANY of the above issues to upgrade both their BIOS to the latest version, as well as their Intel and 3rd party graphics drivers.
Thank you for your patience and understanding!