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      1 /*
      2  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 #ifndef WEBRTC_COMMON_AUDIO_LAPPED_TRANSFORM_H_
     12 #define WEBRTC_COMMON_AUDIO_LAPPED_TRANSFORM_H_
     13 
     14 #include <complex>
     15 
     16 #include "webrtc/base/scoped_ptr.h"
     17 #include "webrtc/common_audio/blocker.h"
     18 #include "webrtc/common_audio/real_fourier.h"
     19 #include "webrtc/system_wrappers/include/aligned_array.h"
     20 
     21 namespace webrtc {
     22 
     23 // Helper class for audio processing modules which operate on frequency domain
     24 // input derived from the windowed time domain audio stream.
     25 //
     26 // The input audio chunk is sliced into possibly overlapping blocks, multiplied
     27 // by a window and transformed with an FFT implementation. The transformed data
     28 // is supplied to the given callback for processing. The processed output is
     29 // then inverse transformed into the time domain and spliced back into a chunk
     30 // which constitutes the final output of this processing module.
     31 class LappedTransform {
     32  public:
     33   class Callback {
     34    public:
     35     virtual ~Callback() {}
     36 
     37     virtual void ProcessAudioBlock(const std::complex<float>* const* in_block,
     38                                    size_t num_in_channels, size_t frames,
     39                                    size_t num_out_channels,
     40                                    std::complex<float>* const* out_block) = 0;
     41   };
     42 
     43   // Construct a transform instance. |chunk_length| is the number of samples in
     44   // each channel. |window| defines the window, owned by the caller (a copy is
     45   // made internally); |window| should have length equal to |block_length|.
     46   // |block_length| defines the length of a block, in samples.
     47   // |shift_amount| is in samples. |callback| is the caller-owned audio
     48   // processing function called for each block of the input chunk.
     49   LappedTransform(size_t num_in_channels,
     50                   size_t num_out_channels,
     51                   size_t chunk_length,
     52                   const float* window,
     53                   size_t block_length,
     54                   size_t shift_amount,
     55                   Callback* callback);
     56   ~LappedTransform() {}
     57 
     58   // Main audio processing helper method. Internally slices |in_chunk| into
     59   // blocks, transforms them to frequency domain, calls the callback for each
     60   // block and returns a de-blocked time domain chunk of audio through
     61   // |out_chunk|. Both buffers are caller-owned.
     62   void ProcessChunk(const float* const* in_chunk, float* const* out_chunk);
     63 
     64   // Get the chunk length.
     65   //
     66   // The chunk length is the number of samples per channel that must be passed
     67   // to ProcessChunk via the parameter in_chunk.
     68   //
     69   // Returns the same chunk_length passed to the LappedTransform constructor.
     70   size_t chunk_length() const { return chunk_length_; }
     71 
     72   // Get the number of input channels.
     73   //
     74   // This is the number of arrays that must be passed to ProcessChunk via
     75   // in_chunk.
     76   //
     77   // Returns the same num_in_channels passed to the LappedTransform constructor.
     78   size_t num_in_channels() const { return num_in_channels_; }
     79 
     80   // Get the number of output channels.
     81   //
     82   // This is the number of arrays that must be passed to ProcessChunk via
     83   // out_chunk.
     84   //
     85   // Returns the same num_out_channels passed to the LappedTransform
     86   // constructor.
     87   size_t num_out_channels() const { return num_out_channels_; }
     88 
     89  private:
     90   // Internal middleware callback, given to the blocker. Transforms each block
     91   // and hands it over to the processing method given at construction time.
     92   class BlockThunk : public BlockerCallback {
     93    public:
     94     explicit BlockThunk(LappedTransform* parent) : parent_(parent) {}
     95 
     96     virtual void ProcessBlock(const float* const* input,
     97                               size_t num_frames,
     98                               size_t num_input_channels,
     99                               size_t num_output_channels,
    100                               float* const* output);
    101 
    102    private:
    103     LappedTransform* const parent_;
    104   } blocker_callback_;
    105 
    106   const size_t num_in_channels_;
    107   const size_t num_out_channels_;
    108 
    109   const size_t block_length_;
    110   const size_t chunk_length_;
    111 
    112   Callback* const block_processor_;
    113   Blocker blocker_;
    114 
    115   rtc::scoped_ptr<RealFourier> fft_;
    116   const size_t cplx_length_;
    117   AlignedArray<float> real_buf_;
    118   AlignedArray<std::complex<float> > cplx_pre_;
    119   AlignedArray<std::complex<float> > cplx_post_;
    120 };
    121 
    122 }  // namespace webrtc
    123 
    124 #endif  // WEBRTC_COMMON_AUDIO_LAPPED_TRANSFORM_H_
    125 
    126