If you still experiencing audio delay when using Avantree Oasis, then pls check below -
1. Does your other Bluetooth device Support aptX Low Latency?
aptX Low Latency takes two sides to achieve - transmission side and receiving side. Check www.aptx.com for the qualified aptX LL products. Some products on the market claim to be aptX LL support, but actually the software inside is NOT well-tuned so the connect codec is not aptX Low latency.
2. Is the current connection under aptX Low Latency or simply aptX or SBC.
Oasis - You should see LED as LL on the screen
Here are scentific numbers about Bluetooth audio delay with different codec >
If you are looking for a aptX Low Latency device, here are your choices from Avantree
Bluetooth Over Ear headphones - Avantree Audition Pro, ANC041
Bluetooth Clip on Adapters (for wired headphones) - Avantree Clipper Pro
Bluetooth Speakers - Avantree 006P
Bluetooth Transmitters - Avantree Priva III, IIA, Oasis, Audikast, 200L, Lock, etc.
Bluetooth Receivers - Avantree Oasis, Roxa Plus, Lock
USB PC Bluetooth adapter - Avantree Leaf