multi_channel_resampler.h revision c2e0dbddbe15c98d52c4786dac06cb8952a8ae6d 
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
15namespace media {
16class AudioBus;
17
18// MultiChannelResampler is a multi channel wrapper for SincResampler; allowing
19// high quality sample rate conversion of multiple channels at once.
20class 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.
31  MultiChannelResampler(int channels, double io_sample_rate_ratio,
32                        const ReadCB& read_cb);
33  virtual ~MultiChannelResampler();
34
35  // Resamples |frames| of data from |read_cb_| into AudioBus.
36  void Resample(AudioBus* audio_bus, int frames);
37
38  // Flush all buffered data and reset internal indices.  Not thread safe, do
39  // not call while Resample() is in progress.
40  void Flush();
41
42  // Update ratio for all SincResamplers.  SetRatio() will cause reconstruction
43  // of the kernels used for resampling.  Not thread safe, do not call while
44  // Resample() is in progress.
45  void SetRatio(double io_sample_rate_ratio);
46
47 private:
48  // SincResampler::ReadCB implementation.  ProvideInput() will be called for
49  // each channel (in channel order) as SincResampler needs more data.
50  void ProvideInput(int channel, float* destination, int frames);
51
52  // Sanity check to ensure that ProvideInput() retrieves the same number of
53  // frames for every channel.
54  int last_frame_count_;
55
56  // Source of data for resampling.
57  ReadCB read_cb_;
58
59  // Each channel has its own high quality resampler.
60  ScopedVector<SincResampler> resamplers_;
61
62  // Buffers for audio data going into SincResampler from ReadCB.
63  scoped_ptr<AudioBus> resampler_audio_bus_;
64  scoped_ptr<AudioBus> wrapped_resampler_audio_bus_;
65  std::vector<float*> resampler_audio_data_;
66
67  // The number of output frames that have successfully been processed during
68  // the current Resample() call.
69  int output_frames_ready_;
70
71  DISALLOW_COPY_AND_ASSIGN(MultiChannelResampler);
72};
73
74}  // namespace media
75
76#endif  // MEDIA_BASE_MULTI_CHANNEL_RESAMPLER_H_
77