What is ampGain phaseGain and depthGain

[Charleszhung]

Hello:
Very thanks for your code. I look forward to ask a few questions about Common modules.
First, I am confused about "ampGain" "phaseGain" and "depthGain".How much are they suitable?
Second, should not be the same of phase buffer and depth buffer? why is different about "phaseGain" and "depthGain" ?
Third, The image about phase and depth has a lot of noise. what should I do? filter and calibration?

Thanks very much