Bluetooth output stream cannot open in Exclusive / Low Latency (negotiated as Shared / PerfMode None)

[greenthings]

When a Bluetooth device is connected, the output stream requests Exclusive sharing mode and Low Latency performance mode, but the actual open result is negotiated as Shared sharing mode and PerformanceMode::None.

Is there any way to ensure Exclusive / Low Latency output when using Bluetooth devices?

Should this be handled with specific code, or does it depend on special hardware or products?

Environment

Device: (ex. Samsung Galaxy S24)

Android version: (ex. Android 16)

Oboe version: (ex. 1.8.0)

Audio API: AAudio

Bluetooth device: (ex. EPOS headset) -> aptX

Code snippet

oboe::AudioStreamBuilder builder;

builder.setAudioApi(oboe::AudioApi::AAudio)
       .setSharingMode(oboe::SharingMode::Exclusive)
       .setPerformanceMode(oboe::PerformanceMode::LowLatency)
       .setFormat(oboe::AudioFormat::Float)
       .setChannelCount(2)
       .setSampleRate(48000)
       .setFramesPerCallback(mPerFrame);

builder.openStream(&stream);

Observed result

The stream always opens with:

SharingMode: Shared
PerformanceMode: None

Expected behavior

The stream should open with:

SharingMode: Exclusive
PerformanceMode: LowLatency

[robertwu1]

This is expected. Not all devices support MMAP in all cases.

For Bluetooth audio, most of the latency is from sending data from the audio hardware to the bluetooth headset via L2CAP. This is because there are large buffer between the audio hardware and the bluetooth headset to supported dropped and missed packets.