it is strange, but after reinstall kernel (after installing your test kernel) lgСamera ceases to record sound (your app too). I installed AlsaMixer (I also installed it for experiments before) and set Analog Left to Off. After that LgCamera starts to record sound (settings: source: MIC; Codec: AMR_NB; Stereo: OFF), your app starts to record sound too (settings: Mic source: MIC; Sampling Rate: 8000; Encoder: AMR_NB; checkbox Stereo is marked on, if the chekbox is unmarked the sound isn't recorded). Mic works only once, after a first record setting Analog left changes to default (Mic2) and starts to record the noise only. That's why before every record you need to set Analog left to off. But this is not stable. After some attempts the sound stoped to recored in any settings of Analog Left.
Test was made on: KK v3; PA Kernel from november 19.
If you don't have any idea, it seems to me that you should try to turn off Mic2 in kernel and see what it's like.