Issue of audio delay (out-sync) when playing movies

Hi, I would like to ask the inquiry about the out-sync problem when configures Raspberry Pi with Volumio. I could confirm that there would have a delay of nearly 1 ~ 1.5s when changing the volume in macOS by using Airplay.

At the same time, Raspberry Pi shows the velocity of Wireless is 80Mbps with 2.4G, as the mac connects to same router with 5G (160 Mbps). Honestly, there would be no problme with lisetning the music, but will occure a big toruble when watching movies. Would you please let me know where the issus is and how could I do to fix it? Is it a problem of velocity of Wifi, or could be dealed with by the configuration of Volumio?

Thank you in advance and have a good day.

Best Regards,

Update: The Volumio version is “volumio-2.296-2017-10-18-pi.img”