Add Cubic Interpolation and lower voice cap

Resolves #56

package.json

@@ -1,6 +1,6 @@
 {
   "name": "SpessaSynth",
-  "version": "3.20.36.4",
+  "version": "3.20.37",
   "type": "module",
   "scripts": {
     "start": "node src/website/server/server.js"

src/spessasynth_lib/synthetizer/synthetizer.js

@@ -29,7 +29,7 @@ import { SoundfontManager } from './synth_soundfont_manager.js'
 
 export const WORKLET_PROCESSOR_NAME = "spessasynth-worklet-system";
 
-export const VOICE_CAP = 450;
+export const VOICE_CAP = 350;
 
 export const DEFAULT_PERCUSSION = 9;
 export const MIDI_CHANNEL_COUNT = 16;

src/spessasynth_lib/synthetizer/worklet_system/main_processor.js

@@ -82,10 +82,9 @@ class SpessaSynthProcessor extends AudioWorkletProcessor
 
         /**
          * Interpolation type used
-         * TODO: cubic interpolation?
          * @type {interpolationTypes}
          */
-        this.interpolationType = interpolationTypes.linear;
+        this.interpolationType = interpolationTypes.fourthOrder;
 
         /**
          * @type {function}

src/spessasynth_lib/synthetizer/worklet_system/worklet_methods/note_on.js

@@ -80,7 +80,7 @@ export function noteOn(channel, midiNote, velocity, enableDebugging = false, sen
         const loopEndOffset = voice.modulatedGenerators[generatorTypes.endloopAddrsOffset] + voice.modulatedGenerators[generatorTypes.endloopAddrsCoarseOffset] * 32768;
         const sm = voice.sample;
         // apply them
-        const clamp = num => Math.max(0, Math.min(sm.sampleData.length, num));
+        const clamp = num => Math.max(0, Math.min(sm.sampleData.length - 1, num));
         sm.cursor = clamp( sm.cursor + cursorStartOffset);
         sm.end = clamp(sm.end + endOffset);
         sm.loopStart = clamp(sm.loopStart + loopStartOffset);

src/spessasynth_lib/synthetizer/worklet_system/worklet_methods/voice_control.js

@@ -4,6 +4,7 @@ import { getLFOValue } from '../worklet_utilities/lfo.js'
 import { customControllers } from '../worklet_utilities/worklet_processor_channel.js'
 import { WorkletModulationEnvelope } from '../worklet_utilities/modulation_envelope.js'
 import {
+    getSampleCubic,
     getSampleLinear,
     getSampleNearest,
     interpolationTypes,
@@ -167,6 +168,9 @@ export function renderVoice(
         case interpolationTypes.nearestNeighbor:
             getSampleNearest(voice, bufferOut);
             break;
+
+        case interpolationTypes.fourthOrder:
+            getSampleCubic(voice, bufferOut);
     }
 
     // lowpass filter

src/spessasynth_lib/synthetizer/worklet_system/worklet_utilities/wavetable_oscillator.js

@@ -57,11 +57,6 @@ export function getSampleLinear(voice, outputBuffer)
     }
     else
     {
-        // check and correct end errors
-        if(sample.end >= sampleData.length)
-        {
-            sample.end = sampleData.length - 1;
-        }
         for (let i = 0; i < outputBuffer.length; i++)
         {
 
@@ -124,11 +119,6 @@ export function getSampleNearest(voice, outputBuffer)
     }
     else
     {
-        // check and correct end errors
-        if(sample.end >= sampleData.length)
-        {
-            sample.end = sampleData.length - 1;
-        }
         for (let i = 0; i < outputBuffer.length; i++)
         {
 
@@ -148,4 +138,98 @@ export function getSampleNearest(voice, outputBuffer)
         }
     }
     sample.cursor = cur;
+}
+
+
+
+/**
+ * Fills the output buffer with raw sample data using cubic interpolation
+ * @param voice {WorkletVoice} the voice we're working on
+ * @param outputBuffer {Float32Array} the output buffer to write to
+ */
+export function getSampleCubic(voice, outputBuffer)
+{
+    const sample = voice.sample;
+    let cur = sample.cursor;
+    const sampleData = sample.sampleData;
+
+    if(sample.isLooping)
+    {
+        const loopLength = sample.loopEnd - sample.loopStart;
+        for (let i = 0; i < outputBuffer.length; i++)
+        {
+            // check for loop
+            while(cur >= sample.loopEnd)
+            {
+                cur -= loopLength;
+            }
+
+            // math comes from
+            // https://stackoverflow.com/questions/1125666/how-do-you-do-bicubic-or-other-non-linear-interpolation-of-re-sampled-audio-da
+
+            // grab the 4 points
+            const y0 = ~~cur;   // point before the cursor. twice bitwise not is just a faster Math.floor
+            let y1 = y0 + 1;    // point after the cursor
+            let y2 = y1 + 1;    // point 1 after the cursor
+            let y3 = y2 + 1;    // point 2 after the cursor
+            const t = cur - y0; // distance from y0 to cursor
+            // y0 is not handled here
+            // as it's math.floor of cur which is handled above
+            if(y1 >= sample.loopEnd) y1 -= loopLength;
+            if(y2 >= sample.loopEnd) y2 -= loopLength;
+            if(y3 >= sample.loopEnd) y3 -= loopLength;
+
+            // grab the samples
+            const x0 = sampleData[y0];
+            const x1 = sampleData[y1];
+            const x2 = sampleData[y2];
+            const x3 = sampleData[y3];
+
+            // interpolate
+            // const c0 = x1
+            const c1 = 0.5 * (x2 - x0);
+            const c2 = x0 - (2.5 * x1) + (2 * x2) - (0.5 * x3);
+            const c3 = (0.5 * (x3 - x0)) + (1.5 * (x1 - x2));
+            outputBuffer[i] = (((((c3 * t) + c2) * t) + c1) * t) + x1;
+
+
+            cur += sample.playbackStep * voice.currentTuningCalculated;
+        }
+    }
+    else
+    {
+        for (let i = 0; i < outputBuffer.length; i++)
+        {
+
+            // math comes from
+            // https://stackoverflow.com/questions/1125666/how-do-you-do-bicubic-or-other-non-linear-interpolation-of-re-sampled-audio-da
+
+            // grab the 4 points
+            const y0 = ~~cur;   // point before the cursor. twice bitwise not is just a faster Math.floor
+            let y1 = y0 + 1;    // point after the cursor
+            let y2 = y1 + 1;    // point 1 after the cursor
+            let y3 = y2 + 1;    // point 2 after the cursor
+            const t = cur - y0; // distance from y0 to cursor
+
+            // flag as finished if needed
+            if(y1 >= sample.end ||
+            y2 >= sample.end ||
+            y3 >= sample.end) {voice.finished = true; return;}
+
+            // grab the samples
+            const x0 = sampleData[y0];
+            const x1 = sampleData[y1];
+            const x2 = sampleData[y2];
+            const x3 = sampleData[y3];
+
+            // interpolate
+            const c1 = 0.5 * (x2 - x0);
+            const c2 = x0 - (2.5 * x1) + (2 * x2) - (0.5 * x3);
+            const c3 = (0.5 * (x3 - x0)) + (1.5 * (x1 - x2));
+            outputBuffer[i] = (((((c3 * t) + c2) * t) + c1) * t) + x1;
+
+            cur += sample.playbackStep * voice.currentTuningCalculated;
+        }
+    }
+    voice.sample.cursor = cur;
 }

src/website/js/locale/locale_files/locale_en/synthesizer_controller/synthesizer_controller.js

@@ -60,7 +60,8 @@ export const synthesizerControllerLocale = {
     interpolation: {
         description: "Select the synthesizer's interpolation method",
         linear: "Linear Interpolation",
-        nearestNeighbor: "Nearest neighbor"
+        nearestNeighbor: "Nearest neighbor",
+        cubic: "Cubic Interpolation"
     },
 
     channelController: channelControllerLocale

src/website/js/locale/locale_files/locale_pl/synthesizer_controller/synthesizer_controller.js

@@ -59,7 +59,8 @@ export const synthesizerControllerLocale = {
     interpolation: {
         description: "Wybierz metodę interpolacji",
         linear: "Interpolacja liniowa",
-        nearestNeighbor: "Najbliższy sąsiad"
+        nearestNeighbor: "Najbliższy sąsiad",
+        cubic: "Interpolacja Sześcienna"
     },
 
     channelController: channelControllerLocale

src/website/js/synthesizer_ui/methods/create_main_controller.js

@@ -187,7 +187,6 @@ export function createMainSynthController()
          */
         const linear = document.createElement("option");
         linear.value = "0";
-        linear.selected = true;
         this.locale.bindObjectProperty(linear, "textContent", LOCALE_PATH + "interpolation.linear");
         interpolation.appendChild(linear);
 
@@ -200,6 +199,16 @@ export function createMainSynthController()
         this.locale.bindObjectProperty(nearest, "textContent", LOCALE_PATH + "interpolation.nearestNeighbor");
         interpolation.appendChild(nearest);
 
+        /**
+         * cubic (default)
+         * @type {HTMLOptionElement}
+         */
+        const cubic = document.createElement("option");
+        cubic.value = "2";
+        cubic.selected = true;
+        this.locale.bindObjectProperty(cubic, "textContent", LOCALE_PATH + "interpolation.cubic");
+        interpolation.appendChild(cubic);
+
         interpolation.onchange = () => {
             this.synth.setInterpolationType(parseInt(interpolation.value));
         }