multi_channel_resampler.h revision 2a99a7e74a7f215066514fe81d2bfa6639d9eddd 
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.
39  void Flush();
40
41 private:
42  // SincResampler::ReadCB implementation.  ProvideInput() will be called for
43  // each channel (in channel order) as SincResampler needs more data.
44  void ProvideInput(int channel, float* destination, int frames);
45
46  // Sanity check to ensure that ProvideInput() retrieves the same number of
47  // frames for every channel.
48  int last_frame_count_;
49
50  // Source of data for resampling.
51  ReadCB read_cb_;
52
53  // Each channel has its own high quality resampler.
54  ScopedVector<SincResampler> resamplers_;
55
56  // Buffers for audio data going into SincResampler from ReadCB.
57  scoped_ptr<AudioBus> resampler_audio_bus_;
58  scoped_ptr<AudioBus> wrapped_resampler_audio_bus_;
59  std::vector<float*> resampler_audio_data_;
60
61  // The number of output frames that have successfully been processed during
62  // the current Resample() call.
63  int output_frames_ready_;
64
65  DISALLOW_COPY_AND_ASSIGN(MultiChannelResampler);
66};
67
68}  // namespace media
69
70#endif  // MEDIA_BASE_MULTI_CHANNEL_RESAMPLER_H_
71