blob: 15eb1f844e51a1a3be594b032dae400dfe499e4a [file] [log] [blame]
* Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
// Based on the WAV file format documentation at
// and
#include "common_audio/wav_header.h"
#include <cstring>
#include <limits>
#include <string>
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "rtc_base/sanitizer.h"
#include "rtc_base/system/arch.h"
namespace webrtc {
namespace {
struct ChunkHeader {
uint32_t ID;
uint32_t Size;
static_assert(sizeof(ChunkHeader) == 8, "ChunkHeader size");
struct RiffHeader {
ChunkHeader header;
uint32_t Format;
// We can't nest this definition in WavHeader, because VS2013 gives an error
// on sizeof(WavHeader::fmt): "error C2070: 'unknown': illegal sizeof operand".
struct FmtSubchunk {
ChunkHeader header;
uint16_t AudioFormat;
uint16_t NumChannels;
uint32_t SampleRate;
uint32_t ByteRate;
uint16_t BlockAlign;
uint16_t BitsPerSample;
static_assert(sizeof(FmtSubchunk) == 24, "FmtSubchunk size");
const uint32_t kFmtSubchunkSize = sizeof(FmtSubchunk) - sizeof(ChunkHeader);
// Simple wav header. It does not include chunks that are not essential to read
// audio samples.
struct WavHeader {
WavHeader(const WavHeader&) = default;
WavHeader& operator=(const WavHeader&) = default;
RiffHeader riff;
FmtSubchunk fmt;
struct {
ChunkHeader header;
} data;
static_assert(sizeof(WavHeader) == kWavHeaderSize, "no padding in header");
static inline void WriteLE16(uint16_t* f, uint16_t x) {
*f = x;
static inline void WriteLE32(uint32_t* f, uint32_t x) {
*f = x;
static inline void WriteFourCC(uint32_t* f, char a, char b, char c, char d) {
*f = static_cast<uint32_t>(a) | static_cast<uint32_t>(b) << 8 |
static_cast<uint32_t>(c) << 16 | static_cast<uint32_t>(d) << 24;
static inline uint16_t ReadLE16(uint16_t x) {
return x;
static inline uint32_t ReadLE32(uint32_t x) {
return x;
static inline std::string ReadFourCC(uint32_t x) {
return std::string(reinterpret_cast<char*>(&x), 4);
#error "Write be-to-le conversion functions"
static inline uint32_t RiffChunkSize(size_t bytes_in_payload) {
return static_cast<uint32_t>(bytes_in_payload + kWavHeaderSize -
static inline uint32_t ByteRate(size_t num_channels,
int sample_rate,
size_t bytes_per_sample) {
return static_cast<uint32_t>(num_channels * sample_rate * bytes_per_sample);
static inline uint16_t BlockAlign(size_t num_channels,
size_t bytes_per_sample) {
return static_cast<uint16_t>(num_channels * bytes_per_sample);
// Finds a chunk having the sought ID. If found, then |readable| points to the
// first byte of the sought chunk data. If not found, the end of the file is
// reached.
bool FindWaveChunk(ChunkHeader* chunk_header,
ReadableWav* readable,
const std::string sought_chunk_id) {
RTC_DCHECK_EQ(sought_chunk_id.size(), 4);
while (true) {
if (readable->Read(chunk_header, sizeof(*chunk_header)) !=
return false; // EOF.
if (ReadFourCC(chunk_header->ID) == sought_chunk_id)
return true; // Sought chunk found.
// Ignore current chunk by skipping its payload.
if (!readable->SeekForward(chunk_header->Size))
return false; // EOF or error.
bool ReadFmtChunkData(FmtSubchunk* fmt_subchunk, ReadableWav* readable) {
// Reads "fmt " chunk payload.
if (readable->Read(&(fmt_subchunk->AudioFormat), kFmtSubchunkSize) !=
return false;
const uint32_t fmt_size = ReadLE32(fmt_subchunk->header.Size);
if (fmt_size != kFmtSubchunkSize) {
// There is an optional two-byte extension field permitted to be present
// with PCM, but which must be zero.
int16_t ext_size;
if (kFmtSubchunkSize + sizeof(ext_size) != fmt_size)
return false;
if (readable->Read(&ext_size, sizeof(ext_size)) != sizeof(ext_size))
return false;
if (ext_size != 0)
return false;
return true;
} // namespace
bool CheckWavParameters(size_t num_channels,
int sample_rate,
WavFormat format,
size_t bytes_per_sample,
size_t num_samples) {
// num_channels, sample_rate, and bytes_per_sample must be positive, must fit
// in their respective fields, and their product must fit in the 32-bit
// ByteRate field.
if (num_channels == 0 || sample_rate <= 0 || bytes_per_sample == 0)
return false;
if (static_cast<uint64_t>(sample_rate) > std::numeric_limits<uint32_t>::max())
return false;
if (num_channels > std::numeric_limits<uint16_t>::max())
return false;
if (static_cast<uint64_t>(bytes_per_sample) * 8 >
return false;
if (static_cast<uint64_t>(sample_rate) * num_channels * bytes_per_sample >
return false;
// format and bytes_per_sample must agree.
switch (format) {
case kWavFormatPcm:
// Other values may be OK, but for now we're conservative:
if (bytes_per_sample != 1 && bytes_per_sample != 2)
return false;
case kWavFormatALaw:
case kWavFormatMuLaw:
if (bytes_per_sample != 1)
return false;
return false;
// The number of bytes in the file, not counting the first ChunkHeader, must
// be less than 2^32; otherwise, the ChunkSize field overflows.
const size_t header_size = kWavHeaderSize - sizeof(ChunkHeader);
const size_t max_samples =
(std::numeric_limits<uint32_t>::max() - header_size) / bytes_per_sample;
if (num_samples > max_samples)
return false;
// Each channel must have the same number of samples.
if (num_samples % num_channels != 0)
return false;
return true;
void WriteWavHeader(uint8_t* buf,
size_t num_channels,
int sample_rate,
WavFormat format,
size_t bytes_per_sample,
size_t num_samples) {
RTC_CHECK(CheckWavParameters(num_channels, sample_rate, format,
bytes_per_sample, num_samples));
auto header = rtc::MsanUninitialized<WavHeader>({});
const size_t bytes_in_payload = bytes_per_sample * num_samples;
WriteFourCC(&header.riff.header.ID, 'R', 'I', 'F', 'F');
WriteLE32(&header.riff.header.Size, RiffChunkSize(bytes_in_payload));
WriteFourCC(&header.riff.Format, 'W', 'A', 'V', 'E');
WriteFourCC(&header.fmt.header.ID, 'f', 'm', 't', ' ');
WriteLE32(&header.fmt.header.Size, kFmtSubchunkSize);
WriteLE16(&header.fmt.AudioFormat, format);
WriteLE16(&header.fmt.NumChannels, static_cast<uint16_t>(num_channels));
WriteLE32(&header.fmt.SampleRate, sample_rate);
ByteRate(num_channels, sample_rate, bytes_per_sample));
WriteLE16(&header.fmt.BlockAlign, BlockAlign(num_channels, bytes_per_sample));
static_cast<uint16_t>(8 * bytes_per_sample));
WriteFourCC(&, 'd', 'a', 't', 'a');
WriteLE32(&, static_cast<uint32_t>(bytes_in_payload));
// Do an extra copy rather than writing everything to buf directly, since buf
// might not be correctly aligned.
memcpy(buf, &header, kWavHeaderSize);
bool ReadWavHeader(ReadableWav* readable,
size_t* num_channels,
int* sample_rate,
WavFormat* format,
size_t* bytes_per_sample,
size_t* num_samples) {
auto header = rtc::MsanUninitialized<WavHeader>({});
// Read RIFF chunk.
if (readable->Read(&header.riff, sizeof(header.riff)) != sizeof(header.riff))
return false;
if (ReadFourCC(header.riff.header.ID) != "RIFF")
return false;
if (ReadFourCC(header.riff.Format) != "WAVE")
return false;
// Find "fmt " and "data" chunks. While the official Wave file specification
// does not put requirements on the chunks order, it is uncommon to find the
// "data" chunk before the "fmt " one. The code below fails if this is not the
// case.
if (!FindWaveChunk(&header.fmt.header, readable, "fmt ")) {
RTC_LOG(LS_ERROR) << "Cannot find 'fmt ' chunk.";
return false;
if (!ReadFmtChunkData(&header.fmt, readable)) {
RTC_LOG(LS_ERROR) << "Cannot read 'fmt ' chunk.";
return false;
if (!FindWaveChunk(&, readable, "data")) {
RTC_LOG(LS_ERROR) << "Cannot find 'data' chunk.";
return false;
// Parse needed fields.
*format = static_cast<WavFormat>(ReadLE16(header.fmt.AudioFormat));
*num_channels = ReadLE16(header.fmt.NumChannels);
*sample_rate = ReadLE32(header.fmt.SampleRate);
*bytes_per_sample = ReadLE16(header.fmt.BitsPerSample) / 8;
const size_t bytes_in_payload = ReadLE32(;
if (*bytes_per_sample == 0)
return false;
*num_samples = bytes_in_payload / *bytes_per_sample;
if (ReadLE32(header.riff.header.Size) < RiffChunkSize(bytes_in_payload))
return false;
if (ReadLE32(header.fmt.ByteRate) !=
ByteRate(*num_channels, *sample_rate, *bytes_per_sample))
return false;
if (ReadLE16(header.fmt.BlockAlign) !=
BlockAlign(*num_channels, *bytes_per_sample))
return false;
return CheckWavParameters(*num_channels, *sample_rate, *format,
*bytes_per_sample, *num_samples);
} // namespace webrtc