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/*
* Copyright (c) 2014 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.
*/
#ifndef WEBRTC_COMMON_AUDIO_LAPPED_TRANSFORM_H_
#define WEBRTC_COMMON_AUDIO_LAPPED_TRANSFORM_H_
#include <complex>
#include "webrtc/base/checks.h"
#include "webrtc/common_audio/blocker.h"
#include "webrtc/common_audio/real_fourier.h"
#include "webrtc/system_wrappers/interface/aligned_array.h"
#include "webrtc/system_wrappers/interface/scoped_ptr.h"
namespace webrtc {
// Helper class for audio processing modules which operate on frequency domain
// input derived from the windowed time domain audio stream.
//
// The input audio chunk is sliced into possibly overlapping blocks, multiplied
// by a window and transformed with an FFT implementation. The transformed data
// is supplied to the given callback for processing. The processed output is
// then inverse transformed into the time domain and spliced back into a chunk
// which constitutes the final output of this processing module.
class LappedTransform {
public:
class Callback {
public:
virtual ~Callback() {}
virtual void ProcessAudioBlock(const std::complex<float>* const* in_block,
int in_channels, int frames,
int out_channels,
std::complex<float>* const* out_block) = 0;
};
// Construct a transform instance. |chunk_length| is the number of samples in
// each channel. |window| defines the window, owned by the caller (a copy is
// made internally); can be NULL to disable windowing entirely.
// |block_length| defines the length of a block, in samples, even when
// windowing is disabled. |shift_length| is in samples. |callback| is the
// caller-owned audio processing function called for each block of the input
// chunk.
LappedTransform(int in_channels, int out_channels, int chunk_length,
const float* window, int block_length, int shift_amount,
Callback* callback);
~LappedTransform();
// Main audio processing helper method. Internally slices |in_chunk| into
// blocks, transforms them to frequency domain, calls the callback for each
// block and returns a de-blocked time domain chunk of audio through
// |out_chunk|. Both buffers are caller-owned.
void ProcessChunk(const float* const* in_chunk, float* const* out_chunk);
private:
// Internal middleware callback, given to the blocker. Transforms each block
// and hands it over to the processing method given at construction time.
friend class BlockThunk;
class BlockThunk : public BlockerCallback {
public:
explicit BlockThunk(LappedTransform* parent) : parent_(parent) {}
virtual ~BlockThunk() {}
virtual void ProcessBlock(const float* const* input, int num_frames,
int num_input_channels, int num_output_channels,
float* const* output);
private:
LappedTransform* parent_;
} blocker_callback_;
int in_channels_;
int out_channels_;
const float* window_;
bool own_window_;
int window_shift_amount_;
int block_length_;
int chunk_length_;
Callback* block_processor_;
scoped_ptr<Blocker> blocker_;
RealFourier fft_;
int cplx_length_;
AlignedArray<float> real_buf_;
AlignedArray<std::complex<float> > cplx_pre_;
AlignedArray<std::complex<float> > cplx_post_;
};
} // namespace webrtc
#endif // WEBRTC_COMMON_AUDIO_LAPPED_TRANSFORM_H_
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