Program sfdiffoc | Diffraction focusing test. 
[SYNOPSIS]
sfdiffoc < inp.rsf > out.rsf v0=SF_EPS v= pad=nt pad2=2*kiss_fft_next_fast_size((n2+1)/2) extend=4
[PARAMETERS]
int     | extend | =4 |   | 	trace extension 
int     | pad | =nt |   | 	padding for stretch 
int     | pad2 | =2*kiss_fft_next_fast_size((n2+1)/2) |   | 	padding for FFT 
float   | v | = |   | 	final velocity 
float   | v0 | =SF_EPS |   | 	initial velocity 
[DIRECTORY]
system/seismic
