Hi Liang,
Please find the answers to your queries:
1) Should these two value be linear value or dB value?
They should be dB values.
2) If they are linear value,yet,from the source code in the "Adjust for threshold" part,I do know these two value is processed with dB value of the maximum sample directly.Why the linear value here mixed up with dB value to finish the calculation?
This is a bug and we will fix this. The Gain and Threshold parameters should be in dB.
3) I have tested a few times.After the post "gain" value changed,however,the output dB value is not to be changed as it should be.Because I have consider the gain should be the make-up gain adding to the output directly.Is there any problem of my point of view?
Your understanding is correct. The reason for no change in the output gain is that the gain parameter is wrong. It is in linear scale instead of dB.
4)Where can I know the converting operation to linear value of the two value in sigma studio?I just always consider all the converting should be listed as formula in the "Default Parameter" tab.Is this just realized by the "slider"?
The liner conversion is done by the slider. You can convert them back to dB using the formula in the 'Default Parameter' tab. Formulas are given below.
Formula for Threshold = 20*log(ThresholdVar)
Formula for Gain = 20*log(GainVar)
Best Regards,
John