Implement ISink and ISource for Android using Oboe

[gavv]

Summary

Add implementations of sndio::ISink, sndio::ISource, and sndio::IBackend using Oboe library (low-latency audio I/O for Android).

The implementation would be similar to pulseaudio backend: roc_sndio/target_pulseaudio.

This page provides more info on audio backends in roc: https://roc-streaming.org/toolkit/docs/internals/audio_backends.html

Implementation

We'll need to add target_oboe target directory to roc_sndio with three new classes:

• OboeSink
• OboeSource
• OboeBackend

(or maybe one class OboeDevice instead of two classes OboeSink+OboeSource, like it's done for pulseaudio).

And then we should register OboeBackend in sndio::BackendDispatcher.

Some notes:

• we likely should use Oboe callback mode, which provides a lower latency;
• we should also implement onErrorAfterClose callback and restart stream if it's disconnected;
• we should use oboe::PerformanceMode::LowLatency and oboe::InputPreset::Unprocessed modes;
• we should ensure to perform resampling only once: either in Oboe or in Roc; so if resampling is enabled in Roc, it should be disabled in Oboe, and vice versa.

Testing

Backend can be tested manually by building roc-send and roc-recv for Android and uploading binaries via adb.

https://roc-streaming.org/toolkit/docs/tools/command_line_tools.html