Which audio format can be recorded and played back by iPhone and Android?

Question

I am designing an app that can record short audio files on iPhone and Android that can be played back on both platforms, as well as hopefully any other smartphone.

Answer 1

As explained above by typo.pl, the generally compatible format is AMR or WAVE(PCM), but in practice, we prefer a progressive solution:

produce AAC on iOS and Android 2.3.3+, but fallback to produce AMR (WB) on Android pre-2.3.3. Both formats are playable on all platforms.

I guess it's a fairly easy solution for better compatibility and audio quality.