Android 10 is now available in its final form on a few phones, but some of its more interesting changes flew under the radar. One of those is a change to how audio inputs work, which allows multiple apps to access audio input at once — in some cases, anyway.
Before Android 10, only one app could access an audio input at once; if an app tried to ask permission to an input while it was in use by something else, the app would be blocked. As of Android 10, audio inputs can be shared by multiple apps, but only in some cases. Google lays out the rules in a new documentation page:
- Privileged apps have higher priority than ordinary apps.
- Apps with visible foreground UIs have higher priority than background apps.
- Apps capturing audio from a privacy-sensitive source have higher priority than apps that are not.
- Two ordinary apps can never capture audio at the same time.
- In some situations, a privileged app can share audio input with another app.
- If two background apps of same priority are capturing audio, the last one started has higher priority.
Simply put, the new system is primarily designed to benefit accessibility services and Google Assistant — accessibility apps can listen for input while a regular app is also listening, and the same goes when Assistant is opened. However, two regular apps can't listen at the same time, one will simply receive silence.
If Google hadn't started cracking down on apps that use accessibility permissions for non-accessibility reasons, this could have allowed for far more interesting uses, like easier call recording applications. Those apps might still be developed, but they won't be allowed inside the Play Store.
Source: Android Developers