Stereo Tool

I'm using Stereo Tool 10.21 as "stand alone" to play my music videos. I use Emby as I really like the user interface.

Stereo Tool takes about 1.5 seconds to process the audio, so image and sound are way out of sync.
Emby player has no apparent way to compensate for this. VLC has track synchronization filters that work, but it's not my favorite player.

All suggestions are much appreciated!

With a virtual device you can probably never reduce latency enough to be able to watch video comfortably with the standalone version - i have tried but wasn't even close.
I use a video player with dsp support (Potplayer) and stereo tool's dsp version - that way there is no noticeable delay and no need for compensation. If your player has dsp support, that would work. If not, you'll probably switch to another player with either dsp support or at least sync support (Potplayer has both).

So the default Buffer Size/Diversity Delay is 1000ms, and this needs to be changed if used for realtime applications, such as video or gaming.

I/O, Audio I/O, Outputs section, HD Output, expand >, then you will be able to see and adjust the delay. The value you land on will depend on the stability of your audio device and APO (WASAPI, ASIO, MME, KS), so it may need to be played around with to find the proper latency. For reference, I landed on 14.2ms for my VAC output using WASAPI. However, I was able to go lower than this for my ASIO device, but I kept it for synchronization.