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/*
* Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "webrtc/modules/audio_processing/high_pass_filter_impl.h"
#include <assert.h>
#include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
#include "webrtc/modules/audio_processing/audio_buffer.h"
#include "webrtc/system_wrappers/include/critical_section_wrapper.h"
#include "webrtc/typedefs.h"
namespace webrtc {
namespace {
const int16_t kFilterCoefficients8kHz[5] =
{3798, -7596, 3798, 7807, -3733};
const int16_t kFilterCoefficients[5] =
{4012, -8024, 4012, 8002, -3913};
struct FilterState {
int16_t y[4];
int16_t x[2];
const int16_t* ba;
};
int InitializeFilter(FilterState* hpf, int sample_rate_hz) {
assert(hpf != NULL);
if (sample_rate_hz == AudioProcessing::kSampleRate8kHz) {
hpf->ba = kFilterCoefficients8kHz;
} else {
hpf->ba = kFilterCoefficients;
}
WebRtcSpl_MemSetW16(hpf->x, 0, 2);
WebRtcSpl_MemSetW16(hpf->y, 0, 4);
return AudioProcessing::kNoError;
}
int Filter(FilterState* hpf, int16_t* data, size_t length) {
assert(hpf != NULL);
int32_t tmp_int32 = 0;
int16_t* y = hpf->y;
int16_t* x = hpf->x;
const int16_t* ba = hpf->ba;
for (size_t i = 0; i < length; i++) {
// y[i] = b[0] * x[i] + b[1] * x[i-1] + b[2] * x[i-2]
// + -a[1] * y[i-1] + -a[2] * y[i-2];
tmp_int32 = y[1] * ba[3]; // -a[1] * y[i-1] (low part)
tmp_int32 += y[3] * ba[4]; // -a[2] * y[i-2] (low part)
tmp_int32 = (tmp_int32 >> 15);
tmp_int32 += y[0] * ba[3]; // -a[1] * y[i-1] (high part)
tmp_int32 += y[2] * ba[4]; // -a[2] * y[i-2] (high part)
tmp_int32 = (tmp_int32 << 1);
tmp_int32 += data[i] * ba[0]; // b[0]*x[0]
tmp_int32 += x[0] * ba[1]; // b[1]*x[i-1]
tmp_int32 += x[1] * ba[2]; // b[2]*x[i-2]
// Update state (input part)
x[1] = x[0];
x[0] = data[i];
// Update state (filtered part)
y[2] = y[0];
y[3] = y[1];
y[0] = static_cast<int16_t>(tmp_int32 >> 13);
y[1] = static_cast<int16_t>(
(tmp_int32 - (static_cast<int32_t>(y[0]) << 13)) << 2);
// Rounding in Q12, i.e. add 2^11
tmp_int32 += 2048;
// Saturate (to 2^27) so that the HP filtered signal does not overflow
tmp_int32 = WEBRTC_SPL_SAT(static_cast<int32_t>(134217727),
tmp_int32,
static_cast<int32_t>(-134217728));
// Convert back to Q0 and use rounding.
data[i] = (int16_t)(tmp_int32 >> 12);
}
return AudioProcessing::kNoError;
}
} // namespace
typedef FilterState Handle;
HighPassFilterImpl::HighPassFilterImpl(const AudioProcessing* apm,
CriticalSectionWrapper* crit)
: ProcessingComponent(),
apm_(apm),
crit_(crit) {}
HighPassFilterImpl::~HighPassFilterImpl() {}
int HighPassFilterImpl::ProcessCaptureAudio(AudioBuffer* audio) {
int err = apm_->kNoError;
if (!is_component_enabled()) {
return apm_->kNoError;
}
assert(audio->num_frames_per_band() <= 160);
for (int i = 0; i < num_handles(); i++) {
Handle* my_handle = static_cast<Handle*>(handle(i));
err = Filter(my_handle,
audio->split_bands(i)[kBand0To8kHz],
audio->num_frames_per_band());
if (err != apm_->kNoError) {
return GetHandleError(my_handle);
}
}
return apm_->kNoError;
}
int HighPassFilterImpl::Enable(bool enable) {
CriticalSectionScoped crit_scoped(crit_);
return EnableComponent(enable);
}
bool HighPassFilterImpl::is_enabled() const {
return is_component_enabled();
}
void* HighPassFilterImpl::CreateHandle() const {
return new FilterState;
}
void HighPassFilterImpl::DestroyHandle(void* handle) const {
delete static_cast<Handle*>(handle);
}
int HighPassFilterImpl::InitializeHandle(void* handle) const {
return InitializeFilter(static_cast<Handle*>(handle),
apm_->proc_sample_rate_hz());
}
int HighPassFilterImpl::ConfigureHandle(void* /*handle*/) const {
return apm_->kNoError; // Not configurable.
}
int HighPassFilterImpl::num_handles_required() const {
return apm_->num_output_channels();
}
int HighPassFilterImpl::GetHandleError(void* handle) const {
// The component has no detailed errors.
assert(handle != NULL);
return apm_->kUnspecifiedError;
}
} // namespace webrtc
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