All of my music is currently stored on a NAS drive which supports DLNA and UPnP. Almost all the music on it is WMA format, with a few in MP3 and AAC format. When streaming my non-WMA music from the NAS using DLNA to a Chromecast Audio, all of it plays fine. However, when I play the WMA files and try to select the Chromecast or iPhone speakers as the output device, underneath these devices there is a message saying ‘IOS and connected AirPlay devices are not capable of playing WMA files’ (for the iPhone speakers) and 'This device is not capable of playing WMA files (for the Chromecast)
I would love the ability to play the WMA music on my NAS drive on Chromecasts and IOS devices, although it may be hard if the device itself does not support the format.