shithub: sox

--- a/sox.1

+++ b/sox.1

@@ -880,6 +880,8 @@

 .TP 10

 equalizer \fIcentral-frequency\fR \fIQ\fR \fIgain\fR

 Apply an equalizer effect. \fIcentral-frequency\fR gives the central frequency in Hz, \fIQ\fR is the Q-factor (see http://en.wikipedia.org/wiki/Q_factor), and \fIgain\fR is the gain or attenuation in dB.

+This effect supports the \fI-o\fR option (see above).

 .TP 10

 fade [ \fItype\fR ] \fIfade-in-length\fR [ \fIstop-time\fR [ \fIfade-out-length\fR ] ]

 Add a fade effect to the beginning, end, or both of the audio data.

--- a/src/equalizer.c

+++ b/src/equalizer.c

@@ -124,6 +124,26 @@

   eq->y[1] = 0; // y[n-1]

   eq->y[2] = 0; // y[n-2]

+  if (effp->globalinfo.octave_plot_effect)

+  {

+    printf(

+      "title('SoX effect: %s gain=%g centre=%g Q=%g (rate=%u)')\n"

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

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

+      "Fs=%u;minF=10;maxF=Fs/2;\n"

+      "axis([minF maxF -25 25])\n"

+      "sweepF=logspace(log10(minF),log10(maxF),200);\n"

+      "grid on\n"

+      "[h,w]=freqz([%f %f %f],[%f %f %f],sweepF,Fs);\n"

+      "semilogx(w,20*log10(h),'b')\n"

+      "pause\n"

+      , effp->name, eq->gain, eq->cfreq, eq->Q

+      , effp->ininfo.rate, effp->ininfo.rate

+      , eq->b[0], eq->b[1], eq->b[2], eq->a[0], eq->a[1], eq->a[2]

+      );

+    exit(0);

+  }

   return (ST_SUCCESS);