Synopsis
		sflffd2_4_c > out.rsf vel=vel.rsf G=G.rsf < source.rsf s1=files1.rsf s2=files2.rsf dt= nt= isx= isz= ax=5.0 az=5.0 factor=5.0/6.0

Parameters
		file G= auxiliary input file name   float ax=5.0 suppress HF parameter   float az=5.0 suppress HF parameter   float dt=   float factor=5.0/6.0 suppress HF parameter   int isx=   int isz=   int nt=   file s1= auxiliary input file name   file s2= auxiliary input file name   file vel= auxiliary input file name