add a sample preview button (hopefully)

the next commit will be about normalizing sample rate

src/engine/engine.cpp

@@ -1485,6 +1485,26 @@ void DivEngine::syncReset() {
   isBusy.unlock();
 }
 
+const int sampleRates[6]={
+  4000, 8000, 11025, 16000, 22050, 32000
+};
+
+void DivEngine::previewSample(int sample) {
+  isBusy.lock();
+  if (sample<0 || sample>(int)song.sample.size()) {
+    sPreview.sample=-1;
+    sPreview.pos=0;
+    isBusy.unlock();
+    return;
+  }
+  blip_clear(bb[2]);
+  blip_set_rates(bb[2],sampleRates[song.sample[sample]->rate],got.rate);
+  prevSample[2]=0;
+  sPreview.pos=0;
+  sPreview.sample=sample;
+  isBusy.unlock();
+}
+
 String DivEngine::getConfigPath() {
   return configPath;
 }
@@ -1942,13 +1962,23 @@ bool DivEngine::init(String outName) {
     return false;
   }
 
+  bb[2]=blip_new(32768);
+  if (bb[2]==NULL) {
+    logE("not enough memory!\n");
+    return false;
+  }
+  
   bbOut[0]=new short[got.bufsize];
   bbOut[1]=new short[got.bufsize];
+  bbOut[2]=new short[got.bufsize];
 
   bbIn[0]=new short[32768];
   bbIn[1]=new short[32768];
+  bbIn[2]=new short[32768];
   bbInLen=32768;
   
+  blip_set_rates(bb[2],44100,got.rate);
+
   for (int i=0; i<64; i++) {
     vibTable[i]=127*sin(((double)i/64.0)*(2*M_PI));
   }

src/engine/engine.h

@@ -92,13 +92,21 @@ class DivEngine {
   String configFile;
   String lastError;
 
+  struct SamplePreview {
+    int sample;
+    unsigned int pos;
+    SamplePreview():
+      sample(-1),
+      pos(0) {}
+  } sPreview;
+
   short vibTable[64];
 
-  blip_buffer_t* bb[2];
+  blip_buffer_t* bb[3];
   size_t bbInLen;
-  int temp[2], prevSample[2];
-  short* bbIn[2];
-  short* bbOut[2];
+  int temp[3], prevSample[3];
+  short* bbIn[3];
+  short* bbOut[3];
 
   size_t totalProcessed;
 
@@ -155,6 +163,9 @@ class DivEngine {
     // reset playback state
     void syncReset();
 
+    // trigger sample preview
+    void previewSample(int sample);
+
     // get config path
     String getConfigPath();
 

src/engine/playback.cpp

@@ -802,9 +802,36 @@ bool DivEngine::nextTick(bool noAccum) {
 }
 
 void DivEngine::nextBuf(float** in, float** out, int inChans, int outChans, unsigned int size) {
+  memset(out[0],0,size*sizeof(float));
+  memset(out[1],0,size*sizeof(float));
+
+  isBusy.lock();
+  if (sPreview.sample>=0 && sPreview.sample<(int)song.sample.size()) {
+    DivSample* s=song.sample[sPreview.sample];
+    size_t prevtotal=blip_clocks_needed(bb[2],size);
+
+    for (size_t i=0; i<prevtotal; i++) {
+      if (sPreview.pos>=s->rendLength) {
+        temp[2]=0;
+      } else {
+        temp[2]=s->rendData[sPreview.pos++];
+      }
+      blip_add_delta(bb[2],i,temp[2]-prevSample[2]);
+      prevSample[2]=temp[2];
+    }
+
+    if (sPreview.pos>=s->rendLength) sPreview.sample=-1;
+
+    blip_end_frame(bb[2],prevtotal);
+    blip_read_samples(bb[2],bbOut[2],size,0);
+    for (size_t i=0; i<size; i++) {
+      out[0][i]+=(float)bbOut[2][i]/32768.0;
+      out[1][i]+=(float)bbOut[2][i]/32768.0;
+    }
+  }
+
   if (!playing || dispatch==NULL) {
-    memset(out[0],0,size*sizeof(float));
-    memset(out[1],0,size*sizeof(float));
+    isBusy.unlock();
     return;
   }
   size_t runtotal=blip_clocks_needed(bb[0],size);
@@ -820,7 +847,6 @@ void DivEngine::nextBuf(float** in, float** out, int inChans, int outChans, unsi
   size_t runLeft=runtotal;
   size_t runPos=0;
   totalProcessed=0;
-  isBusy.lock();
   while (runLeft) {
     if (!remainingLoops) {
       memset(bbIn[0]+runPos,0,runLeft*sizeof(short));
@@ -874,13 +900,13 @@ void DivEngine::nextBuf(float** in, float** out, int inChans, int outChans, unsi
 
   if (dispatch->isStereo()) {
     for (size_t i=0; i<size; i++) {
-      out[0][i]=(float)bbOut[0][i]/16384.0;
-      out[1][i]=(float)bbOut[1][i]/16384.0;
+      out[0][i]+=(float)bbOut[0][i]/16384.0;
+      out[1][i]+=(float)bbOut[1][i]/16384.0;
     }
   } else {
     for (size_t i=0; i<size; i++) {
-      out[0][i]=(float)bbOut[0][i]/16384.0;
-      out[1][i]=(float)bbOut[0][i]/16384.0;
+      out[0][i]+=(float)bbOut[0][i]/16384.0;
+      out[1][i]+=(float)bbOut[0][i]/16384.0;
     }
   }
   isBusy.unlock();

src/gui/gui.cpp

@@ -906,6 +906,10 @@ void FurnaceGUI::drawSampleEdit() {
       if (ImGui::Button("Apply")) {
         e->renderSamplesP();
       }
+      ImGui::SameLine();
+      if (ImGui::Button(ICON_FA_PLAY "##PreviewSample")) {
+        e->previewSample(curSample);
+      }
     }
   }
   if (ImGui::IsWindowFocused()) curWindow=GUI_WINDOW_SAMPLE_EDIT;