1 files changed, 30 insertions, 0 deletions
diff --git a/examples/7_iir_echo.cpp b/examples/7_iir_echo.cpp
new file mode 100644
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--- /dev/null
+++ b/examples/7_iir_echo.cpp
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+/**
+ * 7_iir_echo.cpp
+ * Written by Clyne Sullivan.
+ *
+ * This filter produces an echo of the given input. There are two parameters:
+ * alpha controls the feedback gain, and D controls the echo/delay length.
+ */
+
+Sample* process_data(Samples samples)
+{
+	constexpr float alpha = 0.75;
+	constexpr unsigned int D = 100;
+
+	static Samples output;
+	static Sample prev[D]; // prev[0] = output[0 - D]
+
+	// Do calculations with previous output
+	for (unsigned int i = 0; i < D; i++)
+		output[i] = samples[i] + alpha * (prev[i] - 2048);
+
+	// Do calculations with current samples
+	for (unsigned int i = D; i < SIZE; i++)
+		output[i] = samples[i] + alpha * (output[i - D] - 2048);
+
+	// Save outputs for next computation
+	for (unsigned int i = 0; i < D; i++)
+		prev[i] = output[SIZE - (D - i)];
+
+	return output;
+}