When a long recording stops partway — Android battery saving

"I recorded three hours and got 40 minutes." This is the most common accident with long recordings on Android, and it is almost never the app itself — it is the device's power saving shutting the app down.

Why it stops

To make the battery last, Android is quick to stop apps that have not been touched for a while. Recording runs as a foreground service, which normally exempts it. Manufacturer power saving can be stronger than that, though. Xiaomi, OPPO, vivo, Huawei and Samsung all ship settings that stop apps more aggressively than stock Android does.

Check these first

When a recording stops, work through it in this order.

Had the notification gone? Recording shows one. If it disappeared, the app was killed
Is the file still there? If it plays up to a point, everything up to there was written
Free space. WAV uses several hundred MB per hour
Calls and other apps. Calls and conferencing apps take the microphone away

Exclude it from battery optimisation

Go to Settings → Apps → Audio Recorder → Battery and take it out of optimisation. The wording varies by device: "Don't optimise", "Unrestricted", "Allow background activity" and so on.

Some manufacturers keep a separate list for auto-start, or "protected apps" that may keep running in the background. Excluding the app from battery optimisation alone is not enough if it is not allowed there too.

Before you record

Turn on automatic splitting. If it does stop, the files up to that point are complete
Record while charging. Power saving gets more aggressive at a low battery level
Switch on airplane mode. It stops a call from taking the microphone
Do a short trial run. Leave it recording for ten minutes with the real settings and check it is still going

If it still stops

Leaving the screen on is the most reliable fix. It uses battery, which does not matter if you are charging. For a recording that really matters, use two devices recording separately as the final insurance.

Questions

Can a recording that stopped be recovered?

With splitting on, the completed files are usable as they are. If it was a single file that stopped partway, the written part sometimes survives, but without a finalised header it may not play properly.

Can I use other apps while recording?

Anything that does not need the microphone is fine. Opening a call, conferencing or camera app — which claim the microphone — stops the recording.

Does this happen on iOS too?

iOS has no manufacturer-specific power saving, so this kind of stop is much rarer. Calls, running out of space and other apps taking the microphone are causes there as well.

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