media/base/multi_channel_resampler.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_BASE_MULTI_CHANNEL_RESAMPLER_H_
   6 #define MEDIA_BASE_MULTI_CHANNEL_RESAMPLER_H_
   7
   8 #include <vector>
   9
  10 #include "base/callback.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/memory/scoped_vector.h"
  13 #include "media/base/sinc_resampler.h"
  14
  15 namespace media {
  16 class AudioBus;
  17
  18 // MultiChannelResampler is a multi channel wrapper for SincResampler; allowing
  19 // high quality sample rate conversion of multiple channels at once.
  20 class MEDIA_EXPORT MultiChannelResampler {
  21  public:
  22   // Callback type for providing more data into the resampler.  Expects AudioBus
  23   // to be completely filled with data upon return; zero padded if not enough
  24   // frames are available to satisfy the request.  |frame_delay| is the number
  25   // of output frames already processed and can be used to estimate delay.
  26   typedef base::Callback<void(int frame_delay, AudioBus* audio_bus)> ReadCB;
  27
  28   // Constructs a MultiChannelResampler with the specified |read_cb|, which is
  29   // used to acquire audio data for resampling.  |io_sample_rate_ratio| is the
  30   // ratio of input / output sample rates.  |request_frames| is the size in
  31   // frames of the AudioBus to be filled by |read_cb|.
  32   MultiChannelResampler(int channels,
  33                         double io_sample_rate_ratio,
  34                         size_t request_frames,
  35                         const ReadCB& read_cb);
  36   virtual ~MultiChannelResampler();
  37
  38   // Resamples |frames| of data from |read_cb_| into AudioBus.
  39   void Resample(int frames, AudioBus* audio_bus);
  40
  41   // Flush all buffered data and reset internal indices.  Not thread safe, do
  42   // not call while Resample() is in progress.
  43   void Flush();
  44
  45   // Update ratio for all SincResamplers.  SetRatio() will cause reconstruction
  46   // of the kernels used for resampling.  Not thread safe, do not call while
  47   // Resample() is in progress.
  48   void SetRatio(double io_sample_rate_ratio);
  49
  50   // The maximum size in frames that guarantees Resample() will only make a
  51   // single call to |read_cb_| for more data.
  52   int ChunkSize() const;
  53
  54  private:
  55   // SincResampler::ReadCB implementation.  ProvideInput() will be called for
  56   // each channel (in channel order) as SincResampler needs more data.
  57   void ProvideInput(int channel, int frames, float* destination);
  58
  59   // Source of data for resampling.
  60   ReadCB read_cb_;
  61
  62   // Each channel has its own high quality resampler.
  63   ScopedVector<SincResampler> resamplers_;
  64
  65   // Buffers for audio data going into SincResampler from ReadCB.
  66   scoped_ptr<AudioBus> resampler_audio_bus_;
  67
  68   // To avoid a memcpy() on the first channel we create a wrapped AudioBus where
  69   // the first channel points to the |destination| provided to ProvideInput().
  70   scoped_ptr<AudioBus> wrapped_resampler_audio_bus_;
  71
  72   // The number of output frames that have successfully been processed during
  73   // the current Resample() call.
  74   int output_frames_ready_;
  75
  76   DISALLOW_COPY_AND_ASSIGN(MultiChannelResampler);
  77 };
  78
  79 }  // namespace media
  80
  81 #endif  // MEDIA_BASE_MULTI_CHANNEL_RESAMPLER_H_