Xiaohan-Tian
76 lines
2.5 KiB
TypeScript
76 lines
2.5 KiB
TypeScript
export const SPECTROGRAM_FULL_MIN_MIDI_PITCH = 0;
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export const SPECTROGRAM_FULL_MAX_MIDI_PITCH = 127;
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export const SPECTROGRAM_MIN_MIDI_PITCH = 12; // C0
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export const SPECTROGRAM_MAX_MIDI_PITCH = 107; // B7
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export const SPECTROGRAM_FULL_SEMITONES =
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SPECTROGRAM_FULL_MAX_MIDI_PITCH - SPECTROGRAM_FULL_MIN_MIDI_PITCH + 1;
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export const SPECTROGRAM_VISIBLE_SEMITONES =
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SPECTROGRAM_MAX_MIDI_PITCH - SPECTROGRAM_MIN_MIDI_PITCH + 1;
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export const SPECTROGRAM_ANALYSIS_RESOLUTION_MULTIPLIER = 2;
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export type SpectrogramHeightResolution = 1 | 3 | 5;
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export const SPECTROGRAM_HEIGHT_RESOLUTION_OPTIONS: SpectrogramHeightResolution[] = [1, 3, 5];
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export function normalizeSpectrogramHeightResolution(value: unknown): SpectrogramHeightResolution {
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if (value === 1 || value === 3 || value === 5) {
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return value;
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}
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return 3;
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}
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export function getSpectrogramPitchBinCount(
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resolution: number,
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): number {
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return SPECTROGRAM_FULL_SEMITONES * resolution;
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}
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export function getSpectrogramVisibleBinRange(
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resolution: number,
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): { start: number; end: number } {
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return {
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start: (SPECTROGRAM_MIN_MIDI_PITCH - SPECTROGRAM_FULL_MIN_MIDI_PITCH) * resolution,
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end: (SPECTROGRAM_MAX_MIDI_PITCH - SPECTROGRAM_FULL_MIN_MIDI_PITCH + 1) * resolution,
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};
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}
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export function getSpectrogramAnalysisResolution(
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resolution: SpectrogramHeightResolution,
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): number {
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return resolution * SPECTROGRAM_ANALYSIS_RESOLUTION_MULTIPLIER;
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}
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export function mapMidiPitchToSpectrogramPosition(
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midiPitch: number,
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resolution: number,
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): number | null {
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const pitchOffset = midiPitch - SPECTROGRAM_FULL_MIN_MIDI_PITCH;
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if (pitchOffset < 0 || pitchOffset > SPECTROGRAM_FULL_MAX_MIDI_PITCH) {
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return null;
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}
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// Anchor each MIDI pitch to the center of its semitone band so the
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// rendered ridge lines up with the piano-roll key row rather than a boundary.
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const scaled = pitchOffset * resolution + (resolution - 1) / 2;
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const maxBin = getSpectrogramPitchBinCount(resolution) - 1;
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return Math.max(0, Math.min(maxBin, scaled));
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}
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export function frequencyToMidiPitch(frequency: number): number | null {
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if (!Number.isFinite(frequency) || frequency <= 0) {
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return null;
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}
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return 69 + 12 * Math.log2(frequency / 440);
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}
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export function mapFrequencyToSpectrogramPosition(
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frequency: number,
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resolution: number,
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): number | null {
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const midiPitch = frequencyToMidiPitch(frequency);
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if (midiPitch === null) {
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return null;
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}
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return mapMidiPitchToSpectrogramPosition(midiPitch, resolution);
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}
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