1 // Copyright 2013 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 #include "media/audio/sounds/wav_audio_handler.h"
6
7 #include <algorithm>
8 #include <cstring>
9
10 #include "base/logging.h"
11 #include "base/sys_byteorder.h"
12 #include "media/base/audio_bus.h"
13
14 namespace {
15
16 const char kChunkId[] = "RIFF";
17 const char kFormat[] = "WAVE";
18 const char kSubchunk1Id[] = "fmt ";
19 const char kSubchunk2Id[] = "data";
20
21 // The size of the header of a wav file. The header consists of 'RIFF', 4 bytes
22 // of total data length, and 'WAVE'.
23 const size_t kWavFileHeaderSize = 12;
24
25 // The size of a chunk header in wav file format. A chunk header consists of a
26 // tag ('fmt ' or 'data') and 4 bytes of chunk length.
27 const size_t kChunkHeaderSize = 8;
28
29 // The minimum size of 'fmt' chunk.
30 const size_t kFmtChunkMinimumSize = 16;
31
32 // The offsets of 'fmt' fields.
33 const size_t kAudioFormatOffset = 0;
34 const size_t kChannelOffset = 2;
35 const size_t kSampleRateOffset = 4;
36 const size_t kByteRateOffset = 8;
37 const size_t kBitsPerSampleOffset = 14;
38
39 // Some constants for audio format.
40 const int kAudioFormatPCM = 1;
41
42 // Reads an integer from |data| with |offset|.
ReadInt(const base::StringPiece & data,size_t offset)43 template<typename T> T ReadInt(const base::StringPiece& data, size_t offset) {
44 CHECK_LE(offset + sizeof(T), data.size());
45 T result;
46 memcpy(&result, data.data() + offset, sizeof(T));
47 #if !defined(ARCH_CPU_LITTLE_ENDIAN)
48 result = base::ByteSwap(result);
49 #endif
50 return result;
51 }
52
53 } // namespace
54
55 namespace media {
56
WavAudioHandler(const base::StringPiece & wav_data)57 WavAudioHandler::WavAudioHandler(const base::StringPiece& wav_data)
58 : num_channels_(0),
59 sample_rate_(0),
60 byte_rate_(0),
61 bits_per_sample_(0) {
62 CHECK_LE(kWavFileHeaderSize, wav_data.size()) << "wav data is too small";
63 CHECK(wav_data.starts_with(kChunkId) &&
64 memcmp(wav_data.data() + 8, kFormat, 4) == 0)
65 << "incorrect wav header";
66
67 uint32 total_length = std::min(ReadInt<uint32>(wav_data, 4),
68 static_cast<uint32>(wav_data.size()));
69 uint32 offset = kWavFileHeaderSize;
70 while (offset < total_length) {
71 const int length = ParseSubChunk(wav_data.substr(offset));
72 CHECK_LE(0, length) << "can't parse wav sub-chunk";
73 offset += length;
74 }
75 }
76
~WavAudioHandler()77 WavAudioHandler::~WavAudioHandler() {
78 }
79
AtEnd(size_t cursor) const80 bool WavAudioHandler::AtEnd(size_t cursor) const {
81 return data_.size() <= cursor;
82 }
83
CopyTo(AudioBus * bus,size_t cursor,size_t * bytes_written) const84 bool WavAudioHandler::CopyTo(AudioBus* bus,
85 size_t cursor,
86 size_t* bytes_written) const {
87 if (!bus)
88 return false;
89 if (bus->channels() != num_channels_) {
90 LOG(ERROR) << "Number of channel mismatch.";
91 return false;
92 }
93 if (AtEnd(cursor)) {
94 bus->Zero();
95 return true;
96 }
97 const int remaining_frames = (data_.size() - cursor) / bytes_per_frame_;
98 const int frames = std::min(bus->frames(), remaining_frames);
99 bus->FromInterleaved(data_.data() + cursor, frames, bytes_per_sample_);
100 *bytes_written = frames * bytes_per_frame_;
101 bus->ZeroFramesPartial(frames, bus->frames() - frames);
102 return true;
103 }
104
ParseSubChunk(const base::StringPiece & data)105 int WavAudioHandler::ParseSubChunk(const base::StringPiece& data) {
106 if (data.size() < kChunkHeaderSize)
107 return data.size();
108 uint32 chunk_length = ReadInt<uint32>(data, 4);
109 if (data.starts_with(kSubchunk1Id)) {
110 if (!ParseFmtChunk(data.substr(kChunkHeaderSize, chunk_length)))
111 return -1;
112 } else if (data.starts_with(kSubchunk2Id)) {
113 if (!ParseDataChunk(data.substr(kChunkHeaderSize, chunk_length)))
114 return -1;
115 } else {
116 LOG(ERROR) << "Unknown data chunk: " << data.substr(0, 4) << ".";
117 }
118 return chunk_length + kChunkHeaderSize;
119 }
120
ParseFmtChunk(const base::StringPiece & data)121 bool WavAudioHandler::ParseFmtChunk(const base::StringPiece& data) {
122 if (data.size() < kFmtChunkMinimumSize) {
123 LOG(ERROR) << "Data size " << data.size() << " is too short.";
124 return false;
125 }
126 DCHECK_EQ(ReadInt<uint16>(data, kAudioFormatOffset), kAudioFormatPCM);
127 num_channels_ = ReadInt<uint16>(data, kChannelOffset);
128 sample_rate_ = ReadInt<uint32>(data, kSampleRateOffset);
129 byte_rate_ = ReadInt<uint32>(data, kByteRateOffset);
130 bits_per_sample_ = ReadInt<uint16>(data, kBitsPerSampleOffset);
131 bytes_per_sample_ = bits_per_sample_ >> 3;
132 bytes_per_frame_ = num_channels_ * bytes_per_sample_;
133 return true;
134 }
135
ParseDataChunk(const base::StringPiece & data)136 bool WavAudioHandler::ParseDataChunk(const base::StringPiece& data) {
137 data_ = data;
138 return true;
139 }
140
141 } // namespace media
142