Roughly sorted by quality:

amr_nb in 3gpp < amr_wb in 3gpp < aac_lc in m4a < aac+ in m4a (only in Android 4.0+) < opus in webm (only in android 5+) < pcm in wav (only in android 4.1+)

Taking into consideration the compatibility of the codecs (mainly with Android and with the popular WhatsApp and Telegram messengers), the best options seem to be:

aac_lc in m4a < aac+ in m4a (API >= 16) < vorbis/opus in webm (API >= 21) < pcm in wav (only in android 4.1+)

For a device running API 14, we can use something like this (MediaRecorder.OutputFormat constants):

  • For very low quality/very low bitrate/very long recording times, use AMR-NB in 3GPP container. Parameters summary: 8kHz and bitrate 12.8kbps Works pretty much anywhere.

  • For low quality/low bitrate/long recording times, use AAC in MP4 container, with m4a extension. Works pretty much anywhere. Example code adapted from: https://developer.android.com/guide/topics/media/mediarecorder.html

    private void startRecording() {
       mRecorder = new MediaRecorder();
       mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
       mRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4); // other?
       mRecorder.setOutputFile(mFileName); // end in m4a, for compatibility
       mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC); // AAC_HE, if supported
    
    
       try {
           mRecorder.prepare();
       } catch (IOException e) {
           Log.e(LOG_TAG, "prepare() failed");
       }
    
    
       mRecorder.start();
    }
    
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