AirPlay 2 audio dropouts with iOS 27 beta 2 on iPhone 17 Pro Max — fixed by increasing audio_decoded_buffer_desired_length_in_seconds

[villa1337]

Environment

• iOS version: 27 beta 2
• Device: iPhone 17 Pro Max
• Shairport Sync version: 5.1 (AirPlay 2)
• Platform: Raspberry Pi (Linux) and Fedora Linux
• Audio backend: PipeWire

Symptom

With iOS 27 beta 2, AirPlay 2 audio streams experience frequent dropouts and stuttering when streaming from an iPhone 17 Pro Max. The issue does not appear to affect classic AirPlay (AirPlay 1) mode.

Investigation

The default value of audio_decoded_buffer_desired_length_in_seconds = 1.0 appears to be insufficient to handle the buffering behavior introduced in iOS 27 beta 2. It seems Apple may have changed how AirPlay 2 audio is sent from the device — possibly larger bursts or different timing — which causes the 1-second decoded audio buffer to underrun.

Fix

Increasing the buffer in /etc/shairport-sync.conf resolves the issue completely:

audio_decoded_buffer_desired_length_in_seconds = 5.0;

Notes

• This was tested on two separate machines (Raspberry Pi and Fedora Linux) with the same result
• iOS 27 is currently in beta so this behavior may change in future betas or the final release
• It would be worth investigating whether the default value should be increased, or whether shairport-sync can dynamically adapt the buffer size based on observed stream behavior

[mikebrady]

Very interesting, thanks.

[cwawak]

villa1337, could you help narrow down where the audio is running dry?

1. Test the latest development build, first with audio_decoded_buffer_desired_length_in_seconds omitted, then set to 5.0.
2. Enable diagnostics.statistics = "yes" and log_verbosity = 2.
3. Capture the logs from connection through at least one dropout in each test.
4. Try audio_decoded_buffer_desired_length_in_seconds at 0.75, 1, 2, 3, and 5, and report the lowest stable value.
5. Include shairport-sync -V, --displayConfig, the exact iOS build, and pipewire --version.

Those comparisons should help distinguish changed iOS burst timing, Shairport Sync’s decoded-buffer scheduling, and PipeWire starvation.