The current SL_ANDROID_RECORDING_PRESET_CAMCORDER value forced to use the internal mic.
By using SL_ANDROID_RECORDING_PRESET_VOICE_RECOGNITION, instead, the pulseaudio module will follow the general behavior of the operating system ( if external headset is plugged in, audio source will be the headset, otherwise it will be the internal mic. )
(The value names are not really indicative, this behavior has been found out by trial and error following OpenSLES_AndroidConfiguration.h)
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