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Fix signalinfo handling in example3.c

The example3.c code did not take into account that sox_add_effect()
modifies the "in" signalinfo to reflect the output signal after the
added effect. This could lead to only part of the input being
processed.

--- a/src/example3.c

+++ b/src/example3.c

@@ -44,8 +44,8 @@

 /*

  * On an alsa capable system, plays an audio file starting 10 seconds in.

  * Copes with sample-rate and channel change if necessary since its

- * common for audio drivers to to support subset of rates and channel

- * counts..

+ * common for audio drivers to support a subset of rates and channel

+ * counts.

  * E.g. example3 song2.ogg

  *

  * Can easily be changed to work with other audio device drivers supported

@@ -57,6 +57,7 @@

   static sox_format_t * in, * out; /* input and output files */

   sox_effects_chain_t * chain;

   sox_effect_t * e;

+  sox_signalinfo_t interm_signal;

   char * args[10];

   assert(argc == 2);

@@ -70,20 +71,22 @@

   chain = sox_create_effects_chain(&in->encoding, &out->encoding);

+  interm_signal = in->signal; /* NB: deep copy */

+

   e = sox_create_effect(sox_find_effect("input"));

   args[0] = (char *)in, assert(sox_effect_options(e, 1, args) == SOX_SUCCESS);

-  assert(sox_add_effect(chain, e, &in->signal, &in->signal) == SOX_SUCCESS);

+  assert(sox_add_effect(chain, e, &interm_signal, &in->signal) == SOX_SUCCESS);

   free(e);

   e = sox_create_effect(sox_find_effect("trim"));

   args[0] = "10", assert(sox_effect_options(e, 1, args) == SOX_SUCCESS);

-  assert(sox_add_effect(chain, e, &in->signal, &in->signal) == SOX_SUCCESS);

+  assert(sox_add_effect(chain, e, &interm_signal, &in->signal) == SOX_SUCCESS);

   free(e);

   if (in->signal.rate != out->signal.rate) {

     e = sox_create_effect(sox_find_effect("rate"));

     assert(sox_effect_options(e, 0, NULL) == SOX_SUCCESS);

-    assert(sox_add_effect(chain, e, &in->signal, &out->signal) == SOX_SUCCESS);

+    assert(sox_add_effect(chain, e, &interm_signal, &out->signal) == SOX_SUCCESS);

     free(e);

   }

@@ -90,13 +93,13 @@

   if (in->signal.channels != out->signal.channels) {

     e = sox_create_effect(sox_find_effect("channels"));

     assert(sox_effect_options(e, 0, NULL) == SOX_SUCCESS);

-    assert(sox_add_effect(chain, e, &in->signal, &out->signal) == SOX_SUCCESS);

+    assert(sox_add_effect(chain, e, &interm_signal, &out->signal) == SOX_SUCCESS);

     free(e);

   }

   e = sox_create_effect(sox_find_effect("output"));

   args[0] = (char *)out, assert(sox_effect_options(e, 1, args) == SOX_SUCCESS);

-  assert(sox_add_effect(chain, e, &in->signal, &out->signal) == SOX_SUCCESS);

+  assert(sox_add_effect(chain, e, &interm_signal, &out->signal) == SOX_SUCCESS);

   free(e);

   sox_flow_effects(chain, NULL, NULL);