Revert "Revert "Limit louder effect with a max RMS""

This reverts commit 45cb96f2d4.

src/components/sound-editor/sound-editor.jsx

@@ -265,6 +265,7 @@ const SoundEditor = props => (
                 onClick={props.onSlower}
             />
             <IconButton
+                disabled={props.tooLoud}
                 className={classNames(styles.effectButton, styles.flipInRtl)}
                 img={louderIcon}
                 title={<FormattedMessage {...messages.louder} />}
@@ -340,6 +341,7 @@ SoundEditor.propTypes = {
     onUndo: PropTypes.func.isRequired,
     playhead: PropTypes.number,
     setRef: PropTypes.func,
+    tooLoud: PropTypes.bool.isRequired,
     trimEnd: PropTypes.number,
     trimStart: PropTypes.number
 };

src/containers/sound-editor.jsx

@@ -14,6 +14,8 @@ import log from '../lib/log.js';
 
 const UNDO_STACK_SIZE = 99;
 
+const MAX_RMS = 1.2;
+
 class SoundEditor extends React.Component {
     constructor (props) {
         super(props);
@@ -265,6 +267,15 @@ class SoundEditor extends React.Component {
             }
         });
     }
+    tooLoud () {
+        const numChunks = this.state.chunkLevels.length;
+        const startIndex = this.state.trimStart === null ?
+            0 : Math.floor(this.state.trimStart * numChunks);
+        const endIndex = this.state.trimEnd === null ?
+            numChunks - 1 : Math.ceil(this.state.trimEnd * numChunks);
+        const trimChunks = this.state.chunkLevels.slice(startIndex, endIndex);
+        return Math.max(...trimChunks) > MAX_RMS;
+    }
     getUndoItem () {
         return {
             ...this.copyCurrentBuffer(),
@@ -399,6 +410,7 @@ class SoundEditor extends React.Component {
                 name={this.props.name}
                 playhead={this.state.playhead}
                 setRef={this.setRef}
+                tooLoud={this.tooLoud()}
                 trimEnd={this.state.trimEnd}
                 trimStart={this.state.trimStart}
                 onChangeName={this.handleChangeName}

src/lib/audio/effects/volume-effect.js

@@ -14,8 +14,16 @@ class VolumeEffect {
         this.gain.gain.setValueAtTime(volume, endSeconds);
         this.gain.gain.exponentialRampToValueAtTime(1.0, endSeconds + this.rampLength);
 
+        // Use a waveshaper node to prevent sample values from exceeding -1 or 1.
+        // Without this, gain can cause samples to exceed this range, then they
+        // are clipped on save, and the sound is distorted on load.
+        this.waveShaper = this.audioContext.createWaveShaper();
+        this.waveShaper.curve = new Float32Array([-1, 1]);
+        this.waveShaper.oversample = 'none';
+
         this.input.connect(this.gain);
-        this.gain.connect(this.output);
+        this.gain.connect(this.waveShaper);
+        this.waveShaper.connect(this.output);
     }
 }