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Add render() method to get raw sample data. #18

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d7f6fe5
Add render() method to get raw sample data.
chr15m May 17, 2021
dc448ff
Fix Travis CI standard linting issues.
chr15m May 31, 2021
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17 changes: 17 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -141,6 +141,23 @@ just call `player.pause()` to pause or `player.load()` to load a new MIDI file.
Returns `true` if `destroy()` has been called on the player. Returns `false`
otherwise.

### `player.render()`

Renders the loaded MIDI file to audio data. Returns an array of `Float32Array`s
containing the raw left and right sample data for the entire song. The
`render()` method should only be called once the MIDI file and soundfonts have
been loaded:

```
player.on("loaded", function() {
const arrays = player.render()
console.log(arrays)
})
```

Note: the uncompressed sample data can consume a lot of memory, depending on
the length of the song.

### `player.on('error', (err) => {})`

This event fires if a fatal error occurs in the player, including if a MIDI file
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39 changes: 39 additions & 0 deletions index.js
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Expand Up @@ -148,6 +148,7 @@ class Timidity extends EventEmitter {
this._songPtr = songPtr
this._lib._mid_song_start(this._songPtr)
debugVerbose('Song and instruments are loaded')
this.emit('loaded')
}

_getMissingInstruments (songPtr, missingCount) {
Expand Down Expand Up @@ -258,6 +259,44 @@ class Timidity extends EventEmitter {
}
}

render () {
const songLength = this._lib._mid_song_get_total_time(this._songPtr) / 1000
const buffSize = songLength * SAMPLE_RATE
const _array = new Int16Array(BUFFER_SIZE * 2)
const arrays = [new Float32Array(buffSize), new Float32Array(buffSize)]
let sampleCount = -1
let lastSample = 0

while (sampleCount) {
const byteCount = this._lib._mid_song_read_wave(
this._songPtr,
this._bufferPtr,
BUFFER_SIZE * BYTES_PER_SAMPLE
)
sampleCount = byteCount / BYTES_PER_SAMPLE

if (byteCount) {
_array.set(
this._lib.HEAP16.subarray(this._bufferPtr / 2, (this._bufferPtr + byteCount) / 2)
)

for (let i = 0; i < sampleCount; i++) {
arrays[0][i + lastSample] = _array[i * 2] / 0x7FFF
arrays[1][i + lastSample] = _array[i * 2 + 1] / 0x7FFF
}
lastSample = lastSample + sampleCount
this.emit('progress', lastSample, buffSize)
}
}

// reset in case the user wants to play
this.seek(0)
this.pause()
this._lib._mid_song_start(this._songPtr)

return arrays
}

_onAudioProcess (event) {
const sampleCount = (this._songPtr && this._playing)
? this._readMidiData()
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