Make passthru actually pass the signal thru.

noisicaa/node_lib/passthru/audio.cpp

@@ -35,6 +35,13 @@ PassthruNode::PassthruNode(EngineImpl* engine, uint64_t id)
   : ProcessorNode(engine, id, "noisicaa.node_lib.passthru") {}
 
 Status PassthruNode::run(BlockContext* ctxt, const std::vector<Buffer*>* buffers) {
+  float* in = (float*)buffers->at(0)->data();
+  float* out = (float*)buffers->at(1)->data();
+
+  for (uint32_t smpl = 0 ; smpl < ctxt->block_size ; ++smpl) {
+    *out++ = *in++;
+  }
+
   return Status::Ok();
 }