libstfinv [TASK]: add usage information for new option irtap

src/libs/libstfinv/stfinvfourier.h

@@ -245,7 +245,7 @@ namespace stfinv {
        *   0.5-0.5*cos(pi*(t-Mtt1)/(Mtt2-Mtt1)).
        * - Mtt2<t<Mtt3 will remain unaltered.
        * - Mtt3<=t<=Mtt4 will be scaled by
-       *   0.5+0.5*cos(pi*(t-Mtt1)/(Mtt2-Mtt1)).
+       *   0.5+0.5*cos(pi*(t-Mtt3)/(Mtt4-Mtt3)).
        * - t>Mtt4 will be set to zero.
        *
        * @{

src/libs/libstfinv/usage/stfinvfourier_description_usage.txt

@@ -4,11 +4,12 @@
 # Procedures in the Fourier domain
 # --------------------------------
 Options and parameters in common for procedures in the Fourier domain:
-  fpow2        use power of two for number of coefficients
-  fdiv=d       use integer multiple of d for number of coefficients
-  fpad=f       padding factor
-  tshift=d     delay source correction filter wavelet by d (in seconds)
-               in order to expose acausal components
+  fpow2              use power of two for number of coefficients
+  fdiv=d             use integer multiple of d for number of coefficients
+  fpad=f             padding factor
+  tshift=d           delay source correction filter wavelet by d (in seconds)
+                     in order to expose acausal components
+  irtap=t1,t2,t3,t4  taper impulse response of correction filter
 
 These options define the number of samples N used for the FFT (Fast Fourier
 Transform). This number N should be larger than the number of samples M in the
@@ -35,4 +36,18 @@ Since by definition, the impulse response is output for the time interval of
 the input data, these acausal components can remain unnoticed. The option
 tshift can be used to shift the impulse response as obtained by inverse FFT in
 order to expose acausal components.
+
+A time domain taper can be applied to the impulse response of the correction
+filter by using option irtap. Four time values are given in units of seconds:
+t1, t2, t3, and t4. They must be in increasing order and (t4-t1) must be
+smaller than the total duration of the time series used to represent signals
+internally. Time value are allowed to be negative. Prior to application of the
+correction filter to the time series passed to the algorithm, the correction
+filter is transformed to the time domain, tapered, and then transformed to the
+Fourier domain again. The values of the taper are:
+  - 0                              if       t <  t1
+  - 0.5-0.5*cos(pi*(t-t1)/(t2-t1)) if t1 <= t <= t2
+  - 1                              if t2 <  t <  t3
+  - 0.5+0.5*cos(pi*(t-t3)/(t3-t4)) if t3 <= t <= t4
+  - 0                              if       t >  t4
 # ----- END OF stfinvfourier_description_usage.txt ----- 

src/libs/libstfinv/usage/stfinvfourier_summary_usage.txt

@@ -4,8 +4,9 @@
 Procedures in the Fourier domain
 --------------------------------
 Options and parameters in common for procedures in the Fourier domain:
-  fpow2        use power of two for number of coefficients
-  fdiv=d       use integer multiple of d for number of coefficients
-  fpad=f       padding factor
-  tshift=d     delay source correction filter wavelet by d (in seconds)
+  fpow2              use power of two for number of coefficients
+  fdiv=d             use integer multiple of d for number of coefficients
+  fpad=f             padding factor
+  tshift=d           delay source correction filter wavelet by d (in seconds)
+  irtap=t1,t2,t3,t4  taper impulse response of correction filter
 # ----- END OF stfinvfourier_summary_usage.txt -----