pcm/SoxrResampler: allow multi-threaded resampling

NEWS

@@ -21,6 +21,7 @@ ver 0.20 (not yet released)
 * resampler
   - new block "resampler" in configuration file
     replacing the old "samplerate_converter" setting
+  - soxr: allow multi-threaded resampling
 * reset song priority on playback
 * write database and state file atomically
 * remove dependency on GLib

doc/user.xml

@@ -2392,6 +2392,17 @@ buffer_size: 16384</programlisting>
                   </itemizedlist>
                 </entry>
               </row>
+
+              <row>
+                <entry>
+                  <varname>threads</varname>
+                </entry>
+                <entry>
+                  The number of <application>libsoxr</application>
+                  threads.  "0" means "automatic".  The default is "1"
+                  which disables multi-threading.
+                </entry>
+              </row>
             </tbody>
           </tgroup>
         </informaltable>

src/pcm/SoxrResampler.cxx

@@ -103,7 +103,7 @@ pcm_resample_soxr_global_init(const ConfigBlock &block, Error &error)
 		    "soxr converter '%s'",
 		    soxr_quality_name(recipe));
 
-	const unsigned n_threads = 1;
+	const unsigned n_threads = block.GetBlockValue("threads", 1);
 	soxr_runtime = soxr_runtime_spec(n_threads);
 
 	return true;