blob: 58f5c2dd7ebf0c16886c7b9a958571b164d48139 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
|
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MEDIA_BASE_SINC_RESAMPLER_H_
#define MEDIA_BASE_SINC_RESAMPLER_H_
#include "base/callback.h"
#include "base/memory/scoped_ptr.h"
#include "media/base/media_export.h"
namespace media {
// SincResampler is a high-quality single-channel sample-rate converter.
class MEDIA_EXPORT SincResampler {
public:
// Callback type for providing more data into the resampler. Expects |frames|
// of data to be rendered into |destination|; zero padded if not enough frames
// are available to satisfy the request.
typedef base::Callback<void(float* destination, int frames)> ReadCB;
// Constructs a SincResampler with the specified |read_cb|, which is used to
// acquire audio data for resampling. |io_sample_rate_ratio| is the ratio of
// input / output sample rates.
SincResampler(double io_sample_rate_ratio, const ReadCB& read_cb);
virtual ~SincResampler();
// Resample |frames| of data from |read_cb_| into |destination|.
void Resample(float* destination, int frames);
// The maximum size in frames that guarantees Resample() will only make a
// single call to |read_cb_| for more data.
int ChunkSize();
private:
void InitializeKernel();
// The ratio of input / output sample rates.
double io_sample_rate_ratio_;
// An index on the source input buffer with sub-sample precision. It must be
// double precision to avoid drift.
double virtual_source_idx_;
// The buffer is primed once at the very beginning of processing.
bool buffer_primed_;
// Source of data for resampling.
ReadCB read_cb_;
// Contains kKernelOffsetCount kernels back-to-back, each of size kKernelSize.
// The kernel offsets are sub-sample shifts of a windowed sinc shifted from
// 0.0 to 1.0 sample.
scoped_array<float> kernel_storage_;
// Data from the source is copied into this buffer for each processing pass.
scoped_array<float> input_buffer_;
// Pointers to the various regions inside |input_buffer_|. See the diagram at
// the top of the .cc file for more information.
float* const r0_;
float* const r1_;
float* const r2_;
float* const r3_;
float* const r4_;
float* const r5_;
};
} // namespace media
#endif // MEDIA_BASE_SINC_RESAMPLER_H_
|
