When DSP Buffer Size is set to 'Best latency' the audio plays significantly slower and is crackling on OnePlus 7 Pro

Added support for Android's AAudio engine, so on Android 8.1 and later, Unity Audio is now layered over AAudio. This fixes 4 audio bugs, related to built-in stereo speaker output, built-in vs. Bluetooth microphone selection, Microphone.Start and Microphone.Stop CPU spikes, and low-latency audio output.

In Android OpenSL and AudioTrack, we aren't allowed to mix directly in the audio data callback. This means we have to create a separate audio mixer thread to do our work. On Android, apps cannot create high-priority threads, so our mixer thread is at the mercy of each device's thread scheduler, and sometimes it does not run frequently enough to support a small audio buffer size. This is why "Best Latency" does not work on all devices. We've fixed this bug in Unity 2023.1 by implementing Android AAudio support, which works on Android 8.1 and later (which is currently 85-90% of Android devices). In our AAudio implementation, we are mixing right in the callback, so we do not have this same buffering problem. We are not planning to back-port this change because it is new functionality and it is risky. AAudio has its own set of challenges and we are focusing on making it as robust as possible as 2023.1 matures. One work-around is to just leave the DSP Buffer Size set to the default of "Best Performance". In our testing, this does appear to be enough buffering to be well-supported across all Android devices, with their varying native buffer sizes and varying thread scheduling behaviour.

In Android OpenSL and AudioTrack, we aren't allowed to mix directly in the audio data callback. This means we have to create a separate audio mixer thread to do our work. On Android, apps cannot create high-priority threads, so our mixer thread is at the mercy of each device's thread scheduler, and sometimes it does not run frequently enough to support a small audio buffer size. This is why "Best Latency" does not work on all devices. We've fixed this bug in Unity 2023.1 by implementing Android AAudio support, which works on Android 8.1 and later (which is currently 85-90% of Android devices). In our AAudio implementation, we are mixing right in the callback, so we do not have this same buffering problem. We are not planning to back-port this change because it is new functionality and it is risky. AAudio has its own set of challenges and we are focusing on making it as robust as possible as 2023.1 matures. One work-around is to just leave the DSP Buffer Size set to the default of "Best Performance". In our testing, this does appear to be enough buffering to be well-supported across all Android devices, with their varying native buffer sizes and varying thread scheduling behaviour.

In Android OpenSL and AudioTrack, we aren't allowed to mix directly in the audio data callback. This means we have to create a separate audio mixer thread to do our work. On Android, apps cannot create high-priority threads, so our mixer thread is at the mercy of each device's thread scheduler, and sometimes it does not run frequently enough to support a small audio buffer size. This is why "Best Latency" does not work on all devices. We've fixed this bug in Unity 2023.1 by implementing Android AAudio support, which works on Android 8.1 and later (which is currently 85-90% of Android devices). In our AAudio implementation, we are mixing right in the callback, so we do not have this same buffering problem. We are not planning to back-port this change because it is new functionality and it is risky. AAudio has its own set of challenges and we are focusing on making it as robust as possible as 2023.1 matures. One work-around is to just leave the DSP Buffer Size set to the default of "Best Performance". In our testing, this does appear to be enough buffering to be well-supported across all Android devices, with their varying native buffer sizes and varying thread scheduling behaviour.