Index: third_party/WebKit/Source/platform/audio/IIRFilter.cpp |
diff --git a/third_party/WebKit/Source/platform/audio/IIRFilter.cpp b/third_party/WebKit/Source/platform/audio/IIRFilter.cpp |
index 7b0b87af706b96e0d5ac2a6ce1e487d8f8c29787..5a4a49c96e98f7f955191f999f7504a87b567cf6 100644 |
--- a/third_party/WebKit/Source/platform/audio/IIRFilter.cpp |
+++ b/third_party/WebKit/Source/platform/audio/IIRFilter.cpp |
@@ -9,8 +9,8 @@ |
namespace blink { |
-// The length of the memory buffers for the IIR filter. This MUST be a power of two and must be |
-// greater than the possible length of the filter coefficients. |
+// The length of the memory buffers for the IIR filter. This MUST be a power of |
+// two and must be greater than the possible length of the filter coefficients. |
const int kBufferLength = 32; |
static_assert(kBufferLength >= IIRFilter::kMaxOrder + 1, |
"Internal IIR buffer length must be greater than maximum IIR " |
@@ -34,7 +34,8 @@ void IIRFilter::reset() { |
static std::complex<double> evaluatePolynomial(const double* coef, |
std::complex<double> z, |
int order) { |
- // Use Horner's method to evaluate the polynomial P(z) = sum(coef[k]*z^k, k, 0, order); |
+ // Use Horner's method to evaluate the polynomial P(z) = sum(coef[k]*z^k, k, |
+ // 0, order); |
std::complex<double> result = 0; |
for (int k = order; k >= 0; --k) |
@@ -50,19 +51,20 @@ void IIRFilter::process(const float* sourceP, |
// |
// y[n] = sum(b[k] * x[n - k], k = 0, M) - sum(a[k] * y[n - k], k = 1, N) |
// |
- // where b[k] are the feedforward coefficients and a[k] are the feedback coefficients of the |
- // filter. |
+ // where b[k] are the feedforward coefficients and a[k] are the feedback |
+ // coefficients of the filter. |
- // This is a Direct Form I implementation of an IIR Filter. Should we consider doing a |
- // different implementation such as Transposed Direct Form II? |
+ // This is a Direct Form I implementation of an IIR Filter. Should we |
+ // consider doing a different implementation such as Transposed Direct Form |
+ // II? |
const double* feedback = m_feedback->data(); |
const double* feedforward = m_feedforward->data(); |
ASSERT(feedback); |
ASSERT(feedforward); |
- // Sanity check to see if the feedback coefficients have been scaled appropriately. It must |
- // be EXACTLY 1! |
+ // Sanity check to see if the feedback coefficients have been scaled |
+ // appropriately. It must be EXACTLY 1! |
ASSERT(feedback[0] == 1); |
int feedbackLength = m_feedback->size(); |
@@ -73,8 +75,8 @@ void IIRFilter::process(const float* sourceP, |
double* yBuffer = m_yBuffer.data(); |
for (size_t n = 0; n < framesToProcess; ++n) { |
- // To help minimize roundoff, we compute using double's, even though the filter coefficients |
- // only have single precision values. |
+ // To help minimize roundoff, we compute using double's, even though the |
+ // filter coefficients only have single precision values. |
double yn = feedforward[0] * sourceP[n]; |
// Run both the feedforward and feedback terms together, when possible. |
@@ -91,7 +93,8 @@ void IIRFilter::process(const float* sourceP, |
for (int k = minLength; k < feedbackLength; ++k) |
yn -= feedback[k] * yBuffer[(m_bufferIndex - k) & (kBufferLength - 1)]; |
- // Save the current input and output values in the memory buffers for the next output. |
+ // Save the current input and output values in the memory buffers for the |
+ // next output. |
m_xBuffer[m_bufferIndex] = sourceP[n]; |
m_yBuffer[m_bufferIndex] = yn; |
@@ -105,17 +108,19 @@ void IIRFilter::getFrequencyResponse(int nFrequencies, |
const float* frequency, |
float* magResponse, |
float* phaseResponse) { |
- // Evaluate the z-transform of the filter at the given normalized frequencies from 0 to 1. (One |
- // corresponds to the Nyquist frequency.) |
+ // Evaluate the z-transform of the filter at the given normalized frequencies |
+ // from 0 to 1. (One corresponds to the Nyquist frequency.) |
// |
// The z-tranform of the filter is |
// |
// H(z) = sum(b[k]*z^(-k), k, 0, M) / sum(a[k]*z^(-k), k, 0, N); |
// |
- // The desired frequency response is H(exp(j*omega)), where omega is in [0, 1). |
+ // The desired frequency response is H(exp(j*omega)), where omega is in [0, |
+ // 1). |
// |
- // Let P(x) = sum(c[k]*x^k, k, 0, P) be a polynomial of order P. Then each of the sums in H(z) |
- // is equivalent to evaluating a polynomial at the point 1/z. |
+ // Let P(x) = sum(c[k]*x^k, k, 0, P) be a polynomial of order P. Then each of |
+ // the sums in H(z) is equivalent to evaluating a polynomial at the point |
+ // 1/z. |
for (int k = 0; k < nFrequencies; ++k) { |
// zRecip = 1/z = exp(-j*frequency) |