multi_channel_resampler.h revision a93a17c8d99d686bd4a1511e5504e5e6cc9fcadf 
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.  |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 private:
51  // SincResampler::ReadCB implementation.  ProvideInput() will be called for
52  // each channel (in channel order) as SincResampler needs more data.
53  void ProvideInput(int channel, int frames, float* destination);
54
55  // Source of data for resampling.
56  ReadCB read_cb_;
57
58  // Each channel has its own high quality resampler.
59  ScopedVector<SincResampler> resamplers_;
60
61  // Buffers for audio data going into SincResampler from ReadCB.
62  scoped_ptr<AudioBus> resampler_audio_bus_;
63
64  // To avoid a memcpy() on the first channel we create a wrapped AudioBus where
65  // the first channel points to the |destination| provided to ProvideInput().
66  scoped_ptr<AudioBus> wrapped_resampler_audio_bus_;
67
68  // The number of output frames that have successfully been processed during
69  // the current Resample() call.
70  int output_frames_ready_;
71
72  DISALLOW_COPY_AND_ASSIGN(MultiChannelResampler);
73};
74
75}  // namespace media
76
77#endif  // MEDIA_BASE_MULTI_CHANNEL_RESAMPLER_H_
78