Multicast can wreak havoc on a WiFi network. Clients that are further away from your AP require sending data at a slower rate and APs will try to send the data slow enough so that all clients can receive the traffic. In practice this means a 1mbps multicast stream will take far more than 1% of a 100mbps network and in some cases I have seen it shut down a network entirely. At my day job we disabled receiving multicast (IPTV) feeds over WiFi years ago because we have never seen it work well enough to be worth it.