Wireless digital audio is difficult if one requires both high bandwidth (= uncompressed, high quality) and low latency (<20ms). There have been great strides in the past decade but generally you cannot have both of these features. Many claim "lossless" audio when in fact they do use compression. And often latency is buried in the spec because its unreasonable for "live" stuff like tv, like 100ms+. One doesn't really care about latency if you're just playing music from your system.
I am only aware of a few solutions:
- WIFI, can stream multichannel uncompressed, but of course has pretty high latency.
- Bluetooth. Only uses lossy compression. Apt-X seems to be the best codec (to my ears) with Apt-X low latency achieving CD-quality (again, to my ears) with <40ms.
- Custom solutions from Texas instruments "PurePath" chip-set. Expensive dev boards, and will only do 16-bit 48kHz stereo. Latency I believe is around 20ms. Uncompressed.
- Firing S/PDIF signals through 2.4GHz video senders. I've also done this, there plenty of bandwidth on the video channel - about 5MHz - for S/PDIF. As you've found out these things are wide band, and cover a huge portion of the spectrum. As they are essentially just analogue FM transmitters they are also prone to interference (as well as pooing all over other video senders in the area).
If I were you I would get a bluetooth transmitter module that supports Apt-X Low latency. Avantree have a large selection but there are plenty of no-brand ones on amazon. Along with a receiver that also supports LL you *should* be able to stream pretty good quality audio at a latency you won't notice (hopefully).