First attempt to play any audio after boot results in 30-second delay

This is caused by the Audiodg.exe scanning all .CAT files from

C:\Windows\System32\catroot\{F750E6C3-38EE-11D1-85E5-00C04FC295EE}

The more updates or MUI packs you have installed, the longer it takes for Windows to validate them. I've already reported this to MSFT years ago, but I have no idea if they will ever fix it.

I found the actual cause and a couple of workarounds.

Cause:

The codec l3codeca.acm does not have an embedded signature, and hence Windows needs to look up the proper signature from catroot. If you have a lot of patches in your system, then catroot will be large and the lookup can take a long time.

The whole startup delay is caused by only this single codec(!). This problem seems to be present all the way back to when l3codeca was introduced in Windows.

Workarounds:

1. Disable l3codeca.acm from the registry:

In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Drivers32 find the key with the value C:\Windows\System32\l3codeca.acm and rename it to something else. Example C:\Windows\System32\l3codeca.acm_disabled.

2. Disable the signature check for audio codecs (potential security risk):

In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Audio add DWORD DisableProtectedAudioDG with value 1.