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fix: incorrect triplet feel pair matching #2765

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Merged
Danielku15 merged 1 commit into from
Jul 5, 2026
+126 −51
Merged

fix: incorrect triplet feel pair matching #2765

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10 changes: 8 additions & 2 deletions packages/alphatab/src/midi/MidiFileGenerator.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -853,12 +853,18 @@ export class MidiFileGenerator {
// e.g. the eighth notes on a 4/4 time signature must start exactly on the following
// times to get a triplet feel applied
// 0 480 960 1440 1920 2400 2880 3360
if (beatStart % interval !== 0) {
const pairSlot = interval * 2;
if (beatStart % pairSlot !== 0) {
return null;
}

// ensure next beat matches spec
if (!beat.nextBeat || beat.nextBeat.voice !== beat.voice || beat.playbackDuration !== interval) {
if (
!beat.nextBeat ||
beat.nextBeat.voice !== beat.voice ||
beat.nextBeat.playbackDuration !== interval ||
beat.nextBeat.playbackStart !== beatStart + interval
) {
return null;
}

Expand Down
167 changes: 118 additions & 49 deletions packages/alphatab/test/audio/MidiFileGenerator.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -59,9 +59,10 @@ describe('MidiFileGeneratorTest', () => {
for (let i: number = 0; i < actualEvents.length; i++) {
Logger.info('Test', `i[${i}] ${actualEvents[i]}`);
if (i < expectedEvents.length) {
expect(expectedEvents[i].equals(actualEvents[i]), `i[${i}] expected[${expectedEvents[i]}] !== actual[${actualEvents[i]}]`).toBe(
true
);
expect(
expectedEvents[i].equals(actualEvents[i]),
`i[${i}] expected[${expectedEvents[i]}] !== actual[${actualEvents[i]}]`
).toBe(true);
}
}
expect(actualEvents.length).toBe(expectedEvents.length);
Expand Down Expand Up @@ -614,54 +615,122 @@ describe('MidiFileGeneratorTest', () => {
assertEvents(handler.midiEvents, expectedEvents);
});

it('triplet-feel', () => {
const tex: string =
'\\ts 2 4 \\tf t8 3.2.8*4 | \\tf t16 3.2.16*8 | \\tf d8 3.2.8*4 | \\tf d16 3.2.16*8 | \\tf s8 3.2.8*4 | \\tf s16 3.2.16*8';
const score: Score = parseTex(tex);
// prettier-ignore
const expectedPlaybackStartTimes: number[] = [
0, 480, 960, 1440, 0, 240, 480, 720, 960, 1200, 1440, 1680, 0, 480, 960, 1440, 0, 240, 480, 720, 960, 1200,
1440, 1680, 0, 480, 960, 1440, 0, 240, 480, 720, 960, 1200, 1440, 1680
];
// prettier-ignore
const expectedPlaybackDurations: number[] = [
480, 480, 480, 480, 240, 240, 240, 240, 240, 240, 240, 240, 480, 480, 480, 480, 240, 240, 240, 240, 240,
240, 240, 240, 480, 480, 480, 480, 240, 240, 240, 240, 240, 240, 240, 240
];
const actualPlaybackStartTimes: number[] = [];
const actualPlaybackDurations: number[] = [];
let beat: Beat | null = score.tracks[0].staves[0].bars[0].voices[0].beats[0];
while (beat) {
actualPlaybackStartTimes.push(beat.playbackStart);
actualPlaybackDurations.push(beat.playbackDuration);
beat = beat.nextBeat;
}
expect(actualPlaybackStartTimes.join(',')).toBe(expectedPlaybackStartTimes.join(','));
expect(actualPlaybackDurations.join(',')).toBe(expectedPlaybackDurations.join(','));
// prettier-ignore
const expectedMidiStartTimes: number[] = [
0, 640, 960, 1600, 1920, 2240, 2400, 2720, 2880, 3200, 3360, 3680, 3840, 4560, 4800, 5520, 5760, 6120, 6240,
6600, 6720, 7080, 7200, 7560, 7680, 7920, 8640, 8880, 9600, 9720, 10080, 10200, 10560, 10680, 11040, 11160
];
// prettier-ignore
const expectedMidiDurations: number[] = [
640, 320, 640, 320, 320, 160, 320, 160, 320, 160, 320, 160, 720, 240, 720, 240, 360, 120, 360, 120, 360,
120, 360, 120, 240, 720, 240, 720, 120, 360, 120, 360, 120, 360, 120, 360
];

const actualMidiStartTimes: number[] = [];
const actualMidiDurations: number[] = [];
const handler: FlatMidiEventGenerator = new FlatMidiEventGenerator();
const generator: MidiFileGenerator = new MidiFileGenerator(score, null, handler);
generator.generate();
for (const midiEvent of handler.midiEvents) {
if (midiEvent instanceof FlatNoteEvent) {
actualMidiStartTimes.push(midiEvent.tick);
actualMidiDurations.push(midiEvent.length);
describe('triplet-feel', () => {
function testTripletFeel(
tex: string,
expectedPlaybackStartTimes: number[],
expectedPlaybackDurations: number[],
expectedMidiStartTimes: number[],
expectedMidiDurations: number[]
) {
const score: Score = parseTex(tex);

const actualPlaybackStartTimes: number[] = [];
const actualPlaybackDurations: number[] = [];
let beat: Beat | null = score.tracks[0].staves[0].bars[0].voices[0].beats[0];
while (beat) {
actualPlaybackStartTimes.push(beat.playbackStart);
actualPlaybackDurations.push(beat.playbackDuration);
beat = beat.nextBeat;
}
expect(actualPlaybackStartTimes.join(','), 'expectedPlaybackStartTimes').toBe(
expectedPlaybackStartTimes.join(',')
);
expect(actualPlaybackDurations.join(','), 'expectedPlaybackDurations').toBe(
expectedPlaybackDurations.join(',')
);

const actualMidiStartTimes: number[] = [];
const actualMidiDurations: number[] = [];
const handler: FlatMidiEventGenerator = new FlatMidiEventGenerator();
const generator: MidiFileGenerator = new MidiFileGenerator(score, null, handler);
generator.generate();
for (const midiEvent of handler.midiEvents) {
if (midiEvent instanceof FlatNoteEvent) {
actualMidiStartTimes.push(midiEvent.tick);
actualMidiDurations.push(midiEvent.length);
}
}
expect(actualMidiStartTimes.join(','), 'expectedMidiStartTimes').toBe(expectedMidiStartTimes.join(','));
expect(actualMidiDurations.join(','), 'expectedMidiDurations').toBe(expectedMidiDurations.join(','));
}
expect(actualMidiStartTimes.join(',')).toBe(expectedMidiStartTimes.join(','));
expect(actualMidiDurations.join(',')).toBe(expectedMidiDurations.join(','));

it('variants', () => {
const tex: string =
'\\ts 2 4 \\tf t8 3.2.8*4 | \\tf t16 3.2.16*8 | \\tf d8 3.2.8*4 | \\tf d16 3.2.16*8 | \\tf s8 3.2.8*4 | \\tf s16 3.2.16*8';
const expectedPlaybackStartTimes: number[] = [
0, 480, 960, 1440, 0, 240, 480, 720, 960, 1200, 1440, 1680, 0, 480, 960, 1440, 0, 240, 480, 720, 960,
1200, 1440, 1680, 0, 480, 960, 1440, 0, 240, 480, 720, 960, 1200, 1440, 1680
];
const expectedPlaybackDurations: number[] = [
480, 480, 480, 480, 240, 240, 240, 240, 240, 240, 240, 240, 480, 480, 480, 480, 240, 240, 240, 240, 240,
240, 240, 240, 480, 480, 480, 480, 240, 240, 240, 240, 240, 240, 240, 240
];
const expectedMidiStartTimes: number[] = [
0, 640, 960, 1600, 1920, 2240, 2400, 2720, 2880, 3200, 3360, 3680, 3840, 4560, 4800, 5520, 5760, 6120,
6240, 6600, 6720, 7080, 7200, 7560, 7680, 7920, 8640, 8880, 9600, 9720, 10080, 10200, 10560, 10680,
11040, 11160
];
const expectedMidiDurations: number[] = [
640, 320, 640, 320, 320, 160, 320, 160, 320, 160, 320, 160, 720, 240, 720, 240, 360, 120, 360, 120, 360,
120, 360, 120, 240, 720, 240, 720, 120, 360, 120, 360, 120, 360, 120, 360
];
testTripletFeel(
tex,
expectedPlaybackStartTimes,
expectedPlaybackDurations,
expectedMidiStartTimes,
expectedMidiDurations
);
});

it('not-matching-with-grace', () => {
testTripletFeel(
`
\\tf triplet8th
0.1.8
0.1.8{gr onbeat}
0.1.4
0.1.8
0.1.8
0.1.8
0.1.8
0.1.8 |
0.1.8 * 8
`,
// no swing on playback start/durations
[
// Bar 1
0, 480, 600, 1440, 1920, 2400, 2880, 3360,
// Bar 2
0, 480, 960, 1440, 1920, 2400, 2880, 3360
],
[
// Bar 1
480, 120, 840, 480, 480, 480, 480, 480,
// Bar 2
480, 480, 480, 480, 480, 480, 480, 480
],
// swing on generated midi
[
// Bar 1
// no swing on the first 4 notes as they do not align with the swing definition
0, 480, 600, 1440,
// the last two 8th note pairs swing
1920, 2560, 2880, 3520,
// Bar 2 fully swings
3840, 4480, 4800, 5440, 5760, 6400, 6720, 7360
],
[
// no swing
480, 120, 840, 480,
// the last two 8th note pairs swing
640, 320, 640, 320,
// Swing on second bar
640, 320, 640, 320, 640, 320, 640, 320
]
);
});
});

it('beat-multi-bend', () => {
Expand Down
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