dev159 - add 8-bit dither option

papers/format.md

@@ -32,6 +32,7 @@ these fields are 0 in format versions prior to 100 (0.6pre1).
 
 the format versions are:
 
+- 159: Furnace dev159
 - 158: Furnace 0.6pre5
 - 157: Furnace dev157
 - 156: Furnace dev156
@@ -1232,7 +1233,8 @@ size | description
      | - 2: ping-pong
   1  | flags (>=129) or reserved
      | - 0: BRR emphasis
-  1  | reserved
+  1  | flags 2 (>=159) or reserved
+     | - 0: dither
   4  | loop start
      | - -1 means no loop
   4  | loop end

src/engine/engine.h

@@ -54,8 +54,8 @@
 #define EXTERN_BUSY_BEGIN_SOFT e->softLocked=true; e->isBusy.lock();
 #define EXTERN_BUSY_END e->isBusy.unlock(); e->softLocked=false;
 
-#define DIV_VERSION "0.6pre5"
+#define DIV_VERSION "dev159"
-#define DIV_ENGINE_VERSION 158
+#define DIV_ENGINE_VERSION 159
 // for imports
 #define DIV_VERSION_MOD 0xff01
 #define DIV_VERSION_FC 0xff02

src/engine/sample.cpp

@@ -54,7 +54,7 @@ void DivSample::putSampleData(SafeWriter* w) {
   w->writeC(depth);
   w->writeC(loopMode);
   w->writeC(brrEmphasis);
-  w->writeC(0); // reserved
+  w->writeC(dither);
   w->writeI(loop?loopStart:-1);
   w->writeI(loop?loopEnd:-1);
 
@@ -131,8 +131,11 @@ DivDataErrors DivSample::readSampleData(SafeReader& reader, short version) {
     } else {
       reader.readC();
     }
-    // reserved
+    if (version>=159) {
-    reader.readC();
+      dither=reader.readC()&1;
+    } else {
+      reader.readC();
+    }
 
     loopStart=reader.readI();
     loopEnd=reader.readI();
@@ -1196,8 +1199,23 @@ void DivSample::render(unsigned int formatMask) {
   }
   if (NOT_IN_FORMAT(DIV_SAMPLE_DEPTH_8BIT)) { // 8-bit PCM
     if (!initInternal(DIV_SAMPLE_DEPTH_8BIT,samples)) return;
-    for (unsigned int i=0; i<samples; i++) {
+    if (dither) {
-      data8[i]=data16[i]>>8;
+      unsigned short lfsr=0x6438;
+      unsigned short lfsr1=0x1283;
+      signed char errorLast=0;
+      signed char errorCur=0;
+      for (unsigned int i=0; i<samples; i++) {
+        signed char val=CLAMP(data16[i]+128,-32768,32767)>>8;
+        errorLast=errorCur;
+        errorCur=(val<<8)-data16[i];
+        data8[i]=CLAMP(val-((((errorLast+errorCur)>>1)+(lfsr&0xff))>>8),-128,127);
+        lfsr=(lfsr<<1)|(((lfsr>>1)^(lfsr>>2)^(lfsr>>4)^(lfsr>>15))&1);
+        lfsr1=(lfsr1<<1)|(((lfsr1>>1)^(lfsr1>>2)^(lfsr1>>4)^(lfsr1>>15))&1);
+      }
+    } else {
+      for (unsigned int i=0; i<samples; i++) {
+        data8[i]=data16[i]>>8;
+      }
     }
   }
   if (NOT_IN_FORMAT(DIV_SAMPLE_DEPTH_BRR)) { // BRR
@@ -1277,9 +1295,9 @@ DivSampleHistory* DivSample::prepareUndo(bool data, bool doNotPush) {
       duplicate=new unsigned char[getCurBufLen()];
       memcpy(duplicate,getCurBuf(),getCurBufLen());
     }
-    h=new DivSampleHistory(duplicate,getCurBufLen(),samples,depth,rate,centerRate,loopStart,loopEnd,loop,brrEmphasis,loopMode);
+    h=new DivSampleHistory(duplicate,getCurBufLen(),samples,depth,rate,centerRate,loopStart,loopEnd,loop,brrEmphasis,dither,loopMode);
   } else {
-    h=new DivSampleHistory(depth,rate,centerRate,loopStart,loopEnd,loop,brrEmphasis,loopMode);
+    h=new DivSampleHistory(depth,rate,centerRate,loopStart,loopEnd,loop,brrEmphasis,dither,loopMode);
   }
   if (!doNotPush) {
     while (!redoHist.empty()) {
@@ -1312,6 +1330,8 @@ DivSampleHistory* DivSample::prepareUndo(bool data, bool doNotPush) {
   loopStart=h->loopStart; \
   loopEnd=h->loopEnd; \
   loop=h->loop; \
+  brrEmphasis=h->brrEmphasis; \
+  dither=h->dither; \
   loopMode=h->loopMode;
 
 

src/engine/sample.h

@@ -61,10 +61,10 @@ struct DivSampleHistory {
   unsigned int length, samples;
   DivSampleDepth depth;
   int rate, centerRate, loopStart, loopEnd;
-  bool loop, brrEmphasis;
+  bool loop, brrEmphasis, dither;
   DivSampleLoopMode loopMode;
   bool hasSample;
-  DivSampleHistory(void* d, unsigned int l, unsigned int s, DivSampleDepth de, int r, int cr, int ls, int le, bool lp, bool be, DivSampleLoopMode lm):
+  DivSampleHistory(void* d, unsigned int l, unsigned int s, DivSampleDepth de, int r, int cr, int ls, int le, bool lp, bool be, bool di, DivSampleLoopMode lm):
     data((unsigned char*)d),
     length(l),
     samples(s),
@@ -75,9 +75,10 @@ struct DivSampleHistory {
     loopEnd(le),
     loop(lp),
     brrEmphasis(be),
+    dither(di),
     loopMode(lm),
     hasSample(true) {}
-  DivSampleHistory(DivSampleDepth de, int r, int cr, int ls, int le, bool lp, bool be, DivSampleLoopMode lm):
+  DivSampleHistory(DivSampleDepth de, int r, int cr, int ls, int le, bool lp, bool be, bool di, DivSampleLoopMode lm):
     data(NULL),
     length(0),
     samples(0),
@@ -88,6 +89,7 @@ struct DivSampleHistory {
     loopEnd(le),
     loop(lp),
     brrEmphasis(be),
+    dither(di),
     loopMode(lm),
     hasSample(false) {}
   ~DivSampleHistory();
@@ -108,7 +110,7 @@ struct DivSample {
   // - 10: VOX ADPCM
   // - 16: 16-bit PCM
   DivSampleDepth depth;
-  bool loop, brrEmphasis;
+  bool loop, brrEmphasis, dither;
   // valid values are:
   // - 0: Forward loop
   // - 1: Backward loop
@@ -323,6 +325,7 @@ struct DivSample {
     depth(DIV_SAMPLE_DEPTH_16BIT),
     loop(false),
     brrEmphasis(true),
+    dither(false),
     loopMode(DIV_SAMPLE_LOOP_FORWARD),
     data8(NULL),
     data16(NULL),

src/gui/doAction.cpp

@@ -791,6 +791,8 @@ void FurnaceGUI::doAction(int what) {
               sample->loopEnd=prevSample->loopEnd;
               sample->loop=prevSample->loop;
               sample->loopMode=prevSample->loopMode;
+              sample->brrEmphasis=prevSample->brrEmphasis;
+              sample->dither=prevSample->dither;
               sample->depth=prevSample->depth;
               if (sample->init(prevSample->samples)) {
                 if (prevSample->getCurBuf()!=NULL) {

src/gui/sampleEdit.cpp

@@ -291,6 +291,19 @@ void FurnaceGUI::drawSampleEdit() {
               }
             }
           }
+          if (sample->depth!=DIV_SAMPLE_DEPTH_8BIT && e->getSampleFormatMask()&(1L<<DIV_SAMPLE_DEPTH_8BIT)) {
+            bool di=sample->dither;
+            if (ImGui::Checkbox("8-bit dither",&di)) {
+              sample->prepareUndo(true);
+              sample->dither=di;
+              e->renderSamplesP();
+              updateSampleTex=true;
+              MARK_MODIFIED;
+            }
+            if (ImGui::IsItemHovered()) {
+              ImGui::SetTooltip("dither the sample when used on a chip that only supports 8-bit samples.");
+            }
+          }
 
           int sampleNote=round(64.0+(128.0*12.0*log((double)targetRate/8363.0)/log(2.0)));
           int sampleNoteCoarse=60+(sampleNote>>7);