A simple and modern call recorder app for Android.
- Freebug records all incoming and outgoing across a wide range of apps.
- The app has been tested with the system dialer (Phone app) and WhatsApp on stock Android and GrapheneOS.
- For other apps and OSes, your mileage may vary.
- There is no definitive list of supported apps since Freebug takes an app-agnostic heuristics-based approach.
- Note that due to Android restrictions, caller audio is very muffled (but still fairly audible in quiet environments). This is not a problem when the call is on speakerphone.
- There are currently no customization options to limit recording to specific apps or contacts, or to customize the call detection logic. This may change in the future.
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- A NotificationListenerService watches all notifications come and go.
- Each notification is categorized as a "call" or "not call" notification depending on some simple heuristics.
- We exploit the fact that most call apps show a notification throughout the duration of the call, to tell if a call is ongoing.
- This lets us take an app-agnostic approach (instead of having to write custom code for WhatsApp, Signal, Google Dialer, etc.) — if it looks like a call, we record it (obviously this could lead to false positives, the rates of which should go down as the filtering logic is improved over time).
- To do this properly, we must be able to read all the notification content, even for notifications that Android categorizes as "sensitive" (including call notifications). For this reason, we must have the
RECEIVE_SENSITIVE_NOTIFICATIONSpermission, which can only be granted via ADB.
- If an ongoing call is detected, we use an AccessibilityService to record it.
- An AccessibilityService is used because it is the only kind of service that is allowed to start using the microphone when the recording app is not in the foreground.
- Accessibility services are also much less prone to being killed by battery optimization, so we use it to restart the notification listener if that gets killed off.
- Battery optimization for the app in general also must be turned off to further improve resilience.
- When a call ends, the recording is saved to the Android
Recordingsdirectory, which can be written to without any file access permissions.