It seems a Russian developer created a fork of rtl-sdr that has software decimation. "The decimation feature allows you to sacrifice some bandwidth for increased ADC bit resolution." This may be a reimplementation of the sdr-sharp version of decimation according to this story: http://www.rtl-sdr.com/new-sdr-rtl-sdr-driver-lnamixervga-gain-settings-deci...

The driver also features manual settings for the LNA/Mixer and VGA gain stages and is based on Oliver Jowet’s modified driver.

The source code is here: http://sourceforge.net/projects/sdrr820tmanualgainsettings/files/ if anybody wants to see if there are any notable changes worthy of making a patch or pull for as it may contain other fixes or features.