1 /*
2 * Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 // Based on the WAV file format documentation at
12 // https://ccrma.stanford.edu/courses/422/projects/WaveFormat/ and
13 // http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html
14
15 #include "webrtc/common_audio/wav_header.h"
16
17 #include <algorithm>
18 #include <cstring>
19 #include <limits>
20
21 #include "webrtc/common_audio/include/audio_util.h"
22
23 namespace webrtc {
24
25 struct ChunkHeader {
26 uint32_t ID;
27 uint32_t Size;
28 };
29 COMPILE_ASSERT(sizeof(ChunkHeader) == 8, chunk_header_size);
30
CheckWavParameters(int num_channels,int sample_rate,WavFormat format,int bytes_per_sample,uint32_t num_samples)31 bool CheckWavParameters(int num_channels,
32 int sample_rate,
33 WavFormat format,
34 int bytes_per_sample,
35 uint32_t num_samples) {
36 // num_channels, sample_rate, and bytes_per_sample must be positive, must fit
37 // in their respective fields, and their product must fit in the 32-bit
38 // ByteRate field.
39 if (num_channels <= 0 || sample_rate <= 0 || bytes_per_sample <= 0)
40 return false;
41 if (static_cast<uint64_t>(sample_rate) > std::numeric_limits<uint32_t>::max())
42 return false;
43 if (static_cast<uint64_t>(num_channels) >
44 std::numeric_limits<uint16_t>::max())
45 return false;
46 if (static_cast<uint64_t>(bytes_per_sample) * 8 >
47 std::numeric_limits<uint16_t>::max())
48 return false;
49 if (static_cast<uint64_t>(sample_rate) * num_channels * bytes_per_sample >
50 std::numeric_limits<uint32_t>::max())
51 return false;
52
53 // format and bytes_per_sample must agree.
54 switch (format) {
55 case kWavFormatPcm:
56 // Other values may be OK, but for now we're conservative:
57 if (bytes_per_sample != 1 && bytes_per_sample != 2)
58 return false;
59 break;
60 case kWavFormatALaw:
61 case kWavFormatMuLaw:
62 if (bytes_per_sample != 1)
63 return false;
64 break;
65 default:
66 return false;
67 }
68
69 // The number of bytes in the file, not counting the first ChunkHeader, must
70 // be less than 2^32; otherwise, the ChunkSize field overflows.
71 const uint32_t max_samples =
72 (std::numeric_limits<uint32_t>::max()
73 - (kWavHeaderSize - sizeof(ChunkHeader))) /
74 bytes_per_sample;
75 if (num_samples > max_samples)
76 return false;
77
78 // Each channel must have the same number of samples.
79 if (num_samples % num_channels != 0)
80 return false;
81
82 return true;
83 }
84
85 #ifdef WEBRTC_ARCH_LITTLE_ENDIAN
WriteLE16(uint16_t * f,uint16_t x)86 static inline void WriteLE16(uint16_t* f, uint16_t x) { *f = x; }
WriteLE32(uint32_t * f,uint32_t x)87 static inline void WriteLE32(uint32_t* f, uint32_t x) { *f = x; }
WriteFourCC(uint32_t * f,char a,char b,char c,char d)88 static inline void WriteFourCC(uint32_t* f, char a, char b, char c, char d) {
89 *f = static_cast<uint32_t>(a)
90 | static_cast<uint32_t>(b) << 8
91 | static_cast<uint32_t>(c) << 16
92 | static_cast<uint32_t>(d) << 24;
93 }
94 #else
95 #error "Write be-to-le conversion functions"
96 #endif
97
WriteWavHeader(uint8_t * buf,int num_channels,int sample_rate,WavFormat format,int bytes_per_sample,uint32_t num_samples)98 void WriteWavHeader(uint8_t* buf,
99 int num_channels,
100 int sample_rate,
101 WavFormat format,
102 int bytes_per_sample,
103 uint32_t num_samples) {
104 assert(CheckWavParameters(num_channels, sample_rate, format,
105 bytes_per_sample, num_samples));
106
107 struct {
108 struct {
109 ChunkHeader header;
110 uint32_t Format;
111 } riff;
112 struct {
113 ChunkHeader header;
114 uint16_t AudioFormat;
115 uint16_t NumChannels;
116 uint32_t SampleRate;
117 uint32_t ByteRate;
118 uint16_t BlockAlign;
119 uint16_t BitsPerSample;
120 } fmt;
121 struct {
122 ChunkHeader header;
123 } data;
124 } header;
125 COMPILE_ASSERT(sizeof(header) == kWavHeaderSize, no_padding_in_header);
126
127 const uint32_t bytes_in_payload = bytes_per_sample * num_samples;
128
129 WriteFourCC(&header.riff.header.ID, 'R', 'I', 'F', 'F');
130 WriteLE32(&header.riff.header.Size,
131 bytes_in_payload + kWavHeaderSize - sizeof(ChunkHeader));
132 WriteFourCC(&header.riff.Format, 'W', 'A', 'V', 'E');
133
134 WriteFourCC(&header.fmt.header.ID, 'f', 'm', 't', ' ');
135 WriteLE32(&header.fmt.header.Size, sizeof(header.fmt) - sizeof(ChunkHeader));
136 WriteLE16(&header.fmt.AudioFormat, format);
137 WriteLE16(&header.fmt.NumChannels, num_channels);
138 WriteLE32(&header.fmt.SampleRate, sample_rate);
139 WriteLE32(&header.fmt.ByteRate, (static_cast<uint32_t>(num_channels)
140 * sample_rate * bytes_per_sample));
141 WriteLE16(&header.fmt.BlockAlign, num_channels * bytes_per_sample);
142 WriteLE16(&header.fmt.BitsPerSample, 8 * bytes_per_sample);
143
144 WriteFourCC(&header.data.header.ID, 'd', 'a', 't', 'a');
145 WriteLE32(&header.data.header.Size, bytes_in_payload);
146
147 // Do an extra copy rather than writing everything to buf directly, since buf
148 // might not be correctly aligned.
149 memcpy(buf, &header, kWavHeaderSize);
150 }
151
152 } // namespace webrtc
153