shithub: sox

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add gnuplot support to filter effect

--- a/sox.1

+++ b/sox.1

@@ -1513,7 +1513,7 @@

 need to use the beta parameter at all, unless you are just curious

 about comparing the effects of Blackman-Nuttall vs. Kaiser windows.

 .SP

-This effect supports the \fB\-\-plot octave\fR global option.

+This effect supports the \fB\-\-plot\fR global option.

 .TP

 \fBflanger\fR [\fIdelay depth regen width speed shape phase interp\fR]

 Apply a flanging effect to the audio.

--- a/src/filter.c

+++ b/src/filter.c

@@ -199,6 +199,13 @@

         return (SOX_SUCCESS);

 }

+static int p2(int n)

+{

+  int N;

+  for (N = 1; n; n >>= 1, N <<= 1);

+  return max(N, 1024);

+}

+

 /*

  * Prepare processing.

  */

@@ -268,6 +275,34 @@

         f->Nwin = 2*Xh + 1;  /* not really used afterwards */

         f->Xh = Xh;

         f->Xt = Xh;

+

+   if (effp->global_info->plot == sox_plot_gnuplot) {

+     int N = p2(2 * Xh + 1);

+     double * h = lsx_calloc(N, sizeof(*h));

+     double * H = lsx_malloc((N / 2 + 1) * sizeof(*H));

+     for (i = 1; i < Xh + 1; ++i)

+       h[i - 1] = f->Fp[Xh + 1 - i];

+     for (i = 0; i < Xh + 1; ++i)

+       h[Xh + i] = f->Fp[i];

+     lsx_power_spectrum(N, h, H);

+     free(h);

+     printf(

+       "# gnuplot file\n"

+       "set title 'SoX effect: filter frequency=%g-%g'\n"

+       "set xlabel 'Frequency (Hz)'\n"

+       "set ylabel 'Amplitude Response (dB)'\n"

+       "set grid xtics ytics\n"

+       "set key off\n"

+       "plot '-' with lines\n"

+       , f->freq0, f->freq1);

+     for (i = 0; i <= N/2; ++i)

+       printf("%g %g\n", i * effp->in_signal.rate / N, 10 * log10(H[i]));

+     printf(

+       "e\n"

+       "pause -1 'Hit return to continue'\n");

+     free(H);

+     return SOX_EOF;

+   }

    if (effp->global_info->plot == sox_plot_octave) {

      printf("%% GNU Octave file (may also work with MATLAB(R) )\nb=[");