HI@TC2164,
Welcome to the HP Forum! 🙂 Thank you for becoming a HP Forum member. It is a dynamite location to get help from the community, get suggestions and find what has worked for others. For you have the best experience, here is a link for you to review, should you have any concerns: First Time Here? Learn How to Post and More What is your exact model of Omen 17t gaming notebook? HP Notebook PCs - How Do I Find My Model Number, Serial Number or Product Number? What operating system are you running?
I understand that when using Skype that the sound works on the headset but on speaker after 4 or 5 minutes it quits. You also do not have sound when you try playing Blizzard games. I will assume you are running Windows 8. You have mentioned codec as a possible cause. If you are running Windows 8 here is a link to the Windows 8 Codec Pack (from windows8codecs.com) that you can install. It is also compatible with Windows 10. Here is a link to HP Notebook PCs - No Sound from Speakers (Windows 😎 that may also be of aid. Please let me know the outcome.
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Sparkles1