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feat(generator): implement Hann window function #38

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feat(generator): implement Hann window function #38

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7 changes: 7 additions & 0 deletions src/gen.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@ pub const Generator = struct {
pub fn generate(self: Generator, allocator: std.mem.Allocator, sample: u8) ![]u8 {
var buffer = std.ArrayList(u8).init(allocator);
var i: usize = 0;
const N: f32 = @floatFromInt(sample_count);
while (i < sample_count) : (i += 1) {
// Calculate the frequency according to the equal temperament.
// Hertz = 440 * 2^(semitone distance / 12)
Expand All @@ -45,6 +46,12 @@ pub const Generator = struct {
// Apply the volume control.
const volume: f32 = @floatFromInt(self.config.volume);
amp = amp * volume / 100;

// Apply the Hann window function.
const index: f32 = @floatFromInt(i);
const hann_window = 0.5 * (1.0 - std.math.cos(2.0 * std.math.pi * index / (N - 1)));
amp = amp * hann_window;

try buffer.append(@intFromFloat(amp));
}
return buffer.toOwnedSlice();
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