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-dec…
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.