fix stepbufferwriter

apu/apu.js

@@ -109,7 +109,11 @@ export default class Apu {
     const tndOut = (triangle || noise || dmc) &&
         159.79 / (1 / (triangle / 8227 + noise / 12241 + dmc / 22638) + 100);
 
+    //console.log('volume=' + (pulseOut + tndOut));
     return pulseOut + tndOut;
+
+    // TODO(sdh): consider using the linear approximation and adjusting
+    // all the APU units to output waves centered at zero.
   }
 }
 

audio/stepbufferwriter.js

@@ -16,62 +16,57 @@ export default class StepBufferWriter {
 
     /** @private {number} Current sample index. */
     this.sampleIndex_ = 0;
-    /** @private {number} Last sample value. */
+    /** @private {number} Last sample value read from steps. */
+    this.lastStep_ = 0;
+    /** @private {number} Last sample value written to buffer. */
     this.lastSample_ = 0;
     /** @private {!Array<!Array<number>>} Steps we currently care about. */
     this.steps_ = [];
 
     // this.kernel_ = new StepKernel([[.5, .5], [.5, .5]]);
-    // this.kernel_ = new StepKernel([[1, 0], [0, 1]]);
+    this.kernel_ = new StepKernel([[1, 0], [0, 1]]);
 
     /** @private @const {!StepKernel} */
-    this.kernel_ = lanczosKernel(5, 32);
+    //this.kernel_ = lanczosKernel(5, 32);
   }
 
 
   /**
    * @param {!Array<!Array<number>>} steps Array of [time (s), sample]
    *     indicating transition times between steps.
-   * @param {number} time "Current" ending time.
    * @return {!Promise}
    */
-  write(steps, time) {
-    console.log('WRITE: [' + steps + '], ' + time);
+  write(steps) {
+
+    // TODO(sdh): consider having the input always start at zero?
+
+    //console.log('WRITE: [' + steps.map(s=>`[${s[0]},${s[1]}]`) + ']');
+    if (!steps.length) return new Promise(resolve => setTimeout(resolve, 50));
 
     const samples = [];
-    const endTime = time - 2 * this.kernel_.radius * this.sampleRate_;
-    // Add a final (zero) step.
-    if (steps.length == 0 || steps[steps.length - 1][0] < endTime) {
-
-      // TODO - why aren't we outputting anything for empty steps?!?
-      //   ....?!?
-      //   -- consider separating steps from time, and having
-      //      time just output regardless?  but how to know when ready?
-
-      steps = steps.slice();
-      steps.push([
-        endTime,
-        steps.length ? steps[steps.length - 1][1] : this.lastSample_]);
-    }
+
     for (let step of steps) {
       // console.log('step: ' + step[0] + ', ' + step[1]);
       const s = step[0] * this.sampleRate_;
-      const v = step[1] - this.lastSample_;
+      const v = step[1] - this.lastStep_;
+      this.lastStep_ = step[1];
       //console.log('step: [' + s + ', ' + v + ']');
 
+      // console.log(`step: ${step} s=${s} v=${v} sampleIndex=${this.sampleIndex_} endSample=${Math.floor(s - this.kernel_.radius)}`);
+
       if (s <= this.sampleIndex_) {
-        this.lastSample_ = step[1];
+        this.lastStep_ = this.lastSample_ = step[1];
         this.steps_ = [];
         console.log('past value: resetting');
         continue;
       }
-      this.lastSample_ += v;
+      //this.lastSample_ += v;
 
       // Compute samples until s - kernel.radius
       const endSample = Math.floor(s - this.kernel_.radius);
       if (endSample > this.sampleIndex_) {
         const deltas =
-          this.kernel_.convolve(this.sampleIndex_, endSample, this.steps_)
+            this.kernel_.convolve(this.sampleIndex_, endSample, this.steps_)
         for (let delta of /** @type {!Iterable<number>} */ (deltas)) {
           // TODO(sdh): can we remove the floating-point error drift?!?
           //this.lastSample_ *= 0.9999995;
@@ -88,7 +83,7 @@ export default class StepBufferWriter {
       this.steps_.push([s, v]);
     }
     // now write the buffer.
-    console.log(`Writing ${samples.length} samples`);
+    //console.log(`Writing ${samples.length} samples`, samples);
     return this.buffer_.write(samples);
   }
 }

nsfplayer.js

@@ -52,7 +52,7 @@ export default class NsfPlayer {
     // Yield a single frame worth of steps
     promise = this.promise =
         this.writer.write(this.apu.steps(), this.clock.time)
-            .then(() => this.play(promise));
+            .then(() => { setTimeout(() => this.play(promise), 1); });
     // console.log('Yield data', data);
   }