WASM4 Change Pitch

wasm4-change-pitch.zig

fn changePitchOne(freq: u16, semitones: f32) u16 {
    if (freq == 0) return 0;
    const freq_f32 = @as(f32, @floatFromInt(freq));
    return @intFromFloat(@round(freq_f32 * std.math.pow(
        f32,
        @exp2(1.0 / 12.0),
        semitones,
    )));
}

fn changePitch(tone_arg: u32, semitones: f32) u32 {
    const upper: u32 = changePitchOne(@intCast(tone_arg >> 16), semitones);
    const lower: u32 = changePitchOne(@intCast(tone_arg & 0xffff), semitones);
    return upper << 16 | lower;
}