Tested with AC3 filter for AC3 streams, over system label induced a delay of 1000 ms (time is in miliseconds 1000 ms =1 second) and all is working. The sound is delayed.
Tested with Matrix Mixer for MP3 stream, over system label delay of 1000 ms. Sound delayed.
So, be careful about what you are doing. On my system both thing worked ok. It must work ok on your computer too.