Is there a supported way for a CarPlay audio app to request a lower-latency wireless playback route without communications-style audio processing or restricted volume behavior?
.playback + .default on wired CarPlay gets you ~60ms latency route. The same on wireless CarPlay gets you ~1100ms latency.
I know that wireless CarPlay can support faster connections as I have tested them.
playAndRecord + .default and .playback + .voicePrompt negotiate approximately 160 ms output/presentation latency.
However, on this head unit those paths have unacceptable side effects:
- The duplex route negotiates 24 kHz mono and removes or severely attenuates bass/haptic-engine content.
- The voice-prompt route alters volume semantics: steering-wheel/head-unit volume does not control our app’s level, and it appears to apply voice-oriented EQ or other processing.
- These routes therefore cannot substitute for full-bandwidth media playback, even though their latency is much better.
24 kHz mono would actually work for our app, if only it preserved the signal without voice/telephony EQ, bass removal, or special prompt-bus volume policy.
Is there a documented, supported public API or AVAudioSession configuration (or other API even) that lets a CarPlay audio app request that kind of low-latency wireless media route? If not, is this an intentional limitation of wireless CarPlay media playback, and is there an appropriate enhancement-request path for real-time audio applications?