Ios support Spatial Audio by airplay now

[profoundeye]

Now, iOS 18's AirPlay already supports Spatial Audio (atmos). Will shairport-sync support this? This is a very interesting feature. Let me explain why.

Apple Music supports Spatial Audio and has atmos. To support multi-channel audio, an AVR is usually required for decoding. However, many old AVRs do not support AirPlay. They can only process multi-channel audio through HDMI input data. Considering their outdated code update capabilities, many of these devices will not be updated.

If shairport-sync can support obtaining multi-channel encoding via AirPlay, third-party devices can receive wireless data. Then, old AVR devices can obtain multi-channel support for AirPlay through USB or HDMI.

Currently, similar support can only be obtained through Apple TV.

[mikebrady]

Thanks for the interesting question. There was an announcement about Atmos and HomePods (?) but I haven't followed is up. What form does iOS 18's Atmos support take? As in, how do you get it to work?

[profoundeye]

I anticipate that it operates as follows:
Spatial Audio music works in Apple Music are transmitted to AirPlay terminal devices through AirPlay.
The terminal device transmits to a multi-channel decoder via USB.
After decoding by the decoder, it is transmitted to multi-channel speakers（for example ：5.1）.
It has been confirmed that this can work when the terminal device is an Apple TV.

[mikebrady]

Thanks for this.

Out of curiosity, I did a little experiment:

1. Start playing a track on an iPhone.
2. While playing, using AirPlay, transfer the output to a HomePod mini ("HPm").
3. While still playing, using AirPlay add a Shairport Sync ("SPS") device, so that the HPm and the SPS devices are now playing.

What's interesting about this is that the audio coming to the SPS device is not coming from the iPhone: it's coming from the HPm.

So it looks as if, with iOS 18, Apple have changed things a bit. Now, if an iOS device directs output to an HPm, it effectively hands it off to the HPm; the HPm takes over and the iOS device is no longer involved. Presumably that's how Spatial Audio is handled -- the HPm would be the source, not the iOS device.