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use scratch-audio EffectChain and SoundPlayer in music extension
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- Use AudioEngine to decode sounds
- Store players instead of buffers
- Use SoundPlayer stop event to track concurrency
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@mzgoddard
mzgoddard committed Jun 21, 2018
1 parent 35366d9 commit 9d3502c
Showing 1 changed file with 83 additions and 64 deletions.
147 changes: 83 additions & 64 deletions src/extensions/scratch3_music/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -52,18 +52,25 @@ class Scratch3MusicBlocks {
this._concurrencyCounter = 0;

/**
* An array of audio buffers, one for each drum sound.
* An array of sound players, one for each drum sound.
* @type {Array}
* @private
*/
this._drumBuffers = [];
this._drumPlayers = [];

/**
* An array of arrays of audio buffers. Each instrument has one or more audio buffers.
* An array of arrays of sound players. Each instrument has one or more audio players.
* @type {Array[]}
* @private
*/
this._instrumentBufferArrays = [];
this._instrumentPlayerArrays = [];

/**
* An array of arrays of sound players. Each instrument mya have an audio player for each playable note.
* @type {Array[]}
* @private
*/
this._instrumentPlayerNoteArrays = [];

/**
* An array of audio bufferSourceNodes. Each time you play an instrument or drum sound,
Expand All @@ -87,14 +94,15 @@ class Scratch3MusicBlocks {
const loadingPromises = [];
this.DRUM_INFO.forEach((drumInfo, index) => {
const filePath = `drums/${drumInfo.fileName}`;
const promise = this._storeSound(filePath, index, this._drumBuffers);
const promise = this._storeSound(filePath, index, this._drumPlayers);
loadingPromises.push(promise);
});
this.INSTRUMENT_INFO.forEach((instrumentInfo, instrumentIndex) => {
this._instrumentBufferArrays[instrumentIndex] = [];
this._instrumentPlayerArrays[instrumentIndex] = [];
this._instrumentPlayerNoteArrays[instrumentIndex] = [];
instrumentInfo.samples.forEach((sample, noteIndex) => {
const filePath = `instruments/${instrumentInfo.dirName}/${sample}`;
const promise = this._storeSound(filePath, noteIndex, this._instrumentBufferArrays[instrumentIndex]);
const promise = this._storeSound(filePath, noteIndex, this._instrumentPlayerArrays[instrumentIndex]);
loadingPromises.push(promise);
});
});
Expand All @@ -104,22 +112,22 @@ class Scratch3MusicBlocks {
}

/**
* Decode a sound and store the buffer in an array.
* Decode a sound and store the player in an array.
* @param {string} filePath - the audio file name.
* @param {number} index - the index at which to store the audio buffer.
* @param {array} bufferArray - the array of buffers in which to store it.
* @param {number} index - the index at which to store the audio player.
* @param {array} playerArray - the array of players in which to store it.
* @return {Promise} - a promise which will resolve once the sound has been stored.
*/
_storeSound (filePath, index, bufferArray) {
_storeSound (filePath, index, playerArray) {
const fullPath = `${filePath}.mp3`;

if (!assetData[fullPath]) return;

// The sound buffer has already been downloaded via the manifest file required above.
// The sound player has already been downloaded via the manifest file required above.
const soundBuffer = assetData[fullPath];

return this._decodeSound(soundBuffer).then(buffer => {
bufferArray[index] = buffer;
return this._decodeSound(soundBuffer).then(player => {
playerArray[index] = player;
});
}

Expand All @@ -129,24 +137,14 @@ class Scratch3MusicBlocks {
* @return {Promise} - a promise which will resolve once the sound has decoded.
*/
_decodeSound (soundBuffer) {
const context = this.runtime.audioEngine && this.runtime.audioEngine.audioContext;
const engine = this.runtime.audioEngine;

if (!context) {
if (!engine) {
return Promise.reject(new Error('No Audio Context Detected'));
}

// Check for newer promise-based API
if (context.decodeAudioData.length === 1) {
return context.decodeAudioData(soundBuffer);
} else { // eslint-disable-line no-else-return
// Fall back to callback API
return new Promise((resolve, reject) =>
context.decodeAudioData(soundBuffer,
buffer => resolve(buffer),
error => reject(error)
)
);
}
return engine.decodeSoundPlayer({data: {buffer: soundBuffer}});
}

/**
Expand Down Expand Up @@ -774,26 +772,32 @@ class Scratch3MusicBlocks {
*/
_playDrumNum (util, drumNum) {
if (util.runtime.audioEngine === null) return;
if (util.target.audioPlayer === null) return;
if (util.target.sprite.soundBank === null) return;
// If we're playing too many sounds, do not play the drum sound.
if (this._concurrencyCounter > Scratch3MusicBlocks.CONCURRENCY_LIMIT) {
return;
}
const outputNode = util.target.audioPlayer.getInputNode();
const context = util.runtime.audioEngine.audioContext;
const bufferSource = context.createBufferSource();
bufferSource.buffer = this._drumBuffers[drumNum];
bufferSource.connect(outputNode);
bufferSource.start();

const bufferSourceIndex = this._bufferSources.length;
this._bufferSources.push(bufferSource);
const player = this._drumPlayers[drumNum];

if (player.isPlaying) {
// Take the internal player state and create a new player with it.
// `.play` does this internally but then instructs the sound to
// stop.
player.take();
}

const engine = util.runtime.audioEngine;
const chain = engine.createEffectChain();
chain.setEffectsFromTarget(util.target);
player.connect(chain);

this._concurrencyCounter++;
bufferSource.onended = () => {
player.once('stop', () => {
this._concurrencyCounter--;
delete this._bufferSources[bufferSourceIndex];
};
});

player.play();
}

/**
Expand Down Expand Up @@ -852,7 +856,7 @@ class Scratch3MusicBlocks {
*/
_playNote (util, note, durationSec) {
if (util.runtime.audioEngine === null) return;
if (util.target.audioPlayer === null) return;
if (util.target.sprite.soundBank === null) return;

// If we're playing too many sounds, do not play the note.
if (this._concurrencyCounter > Scratch3MusicBlocks.CONCURRENCY_LIMIT) {
Expand All @@ -867,28 +871,37 @@ class Scratch3MusicBlocks {
const sampleIndex = this._selectSampleIndexForNote(note, sampleArray);

// If the audio sample has not loaded yet, bail out
if (typeof this._instrumentBufferArrays[inst] === 'undefined') return;
if (typeof this._instrumentBufferArrays[inst][sampleIndex] === 'undefined') return;
if (typeof this._instrumentPlayerArrays[inst] === 'undefined') return;
if (typeof this._instrumentPlayerArrays[inst][sampleIndex] === 'undefined') return;

// Create the audio buffer to play the note, and set its pitch
const context = util.runtime.audioEngine.audioContext;
const bufferSource = context.createBufferSource();
// Fetch the sound player to play the note.
const engine = util.runtime.audioEngine;

const bufferSourceIndex = this._bufferSources.length;
this._bufferSources.push(bufferSource);
if (!this._instrumentPlayerNoteArrays[inst][note]) {
this._instrumentPlayerNoteArrays[inst][note] = this._instrumentPlayerArrays[inst][sampleIndex].take();
}

bufferSource.buffer = this._instrumentBufferArrays[inst][sampleIndex];
const sampleNote = sampleArray[sampleIndex];
bufferSource.playbackRate.value = this._ratioForPitchInterval(note - sampleNote);
const player = this._instrumentPlayerNoteArrays[inst][note];

if (player.isPlaying) {
// Take the internal player state and create a new player with it.
// `.play` does this internally but then instructs the sound to
// stop.
player.take();
}

// Create a gain node for this note, and connect it to the sprite's audioPlayer.
const gainNode = context.createGain();
bufferSource.connect(gainNode);
const outputNode = util.target.audioPlayer.getInputNode();
gainNode.connect(outputNode);
const chain = engine.createEffectChain()
chain.setEffectsFromTarget(util.target);

// Start playing the note
bufferSource.start();
// Set its pitch.
const sampleNote = sampleArray[sampleIndex];
const notePitchInterval = this._ratioForPitchInterval(note - sampleNote);

// Create a gain node for this note, and connect it to the sprite's
// simulated effectChain.
const context = engine.audioContext;
const releaseGain = context.createGain();
releaseGain.connect(chain.getInputNode());

// Schedule the release of the note, ramping its gain down to zero,
// and then stopping the sound.
Expand All @@ -898,16 +911,22 @@ class Scratch3MusicBlocks {
}
const releaseStart = context.currentTime + durationSec;
const releaseEnd = releaseStart + releaseDuration;
gainNode.gain.setValueAtTime(1, releaseStart);
gainNode.gain.linearRampToValueAtTime(0.0001, releaseEnd);
bufferSource.stop(releaseEnd);
releaseGain.gain.setValueAtTime(1, releaseStart);
releaseGain.gain.linearRampToValueAtTime(0.0001, releaseEnd);

// Update the concurrency counter
this._concurrencyCounter++;
bufferSource.onended = () => {
player.once('stop', () => {
this._concurrencyCounter--;
delete this._bufferSources[bufferSourceIndex];
};
});

// Start playing the note
player.play();
// Connect the player to the gain node.
player.connect({getInputNode() {return releaseGain;}});
// Set playback now after play creates the outputNode.
player.outputNode.playbackRate.value = notePitchInterval;
// Schedule playback to stop.
player.outputNode.stop(releaseEnd);
}

/**
Expand Down

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