common_audio/wav_header.cc - src - Git at Google

 /*
  *  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
 // https://ccrma.stanford.edu/courses/422/projects/WaveFormat/ and
 // http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html

 #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 {

 #ifndef WEBRTC_ARCH_LITTLE_ENDIAN
 #error "Code not working properly for big endian platforms."
 #endif

 #pragma pack(2)
 struct ChunkHeader {
   uint32_t ID;
   uint32_t Size;
 };
 static_assert(sizeof(ChunkHeader) == 8, "ChunkHeader size");

 #pragma pack(2)
 struct RiffHeader {
   ChunkHeader header;
   uint32_t Format;
 };
 static_assert(sizeof(RiffHeader) == sizeof(ChunkHeader) + 4, "RiffHeader size");

 // We can't nest this definition in WavHeader, because VS2013 gives an error
 // on sizeof(WavHeader::fmt): "error C2070: 'unknown': illegal sizeof operand".
 #pragma pack(2)
 struct FmtPcmSubchunk {
   ChunkHeader header;
   uint16_t AudioFormat;
   uint16_t NumChannels;
   uint32_t SampleRate;
   uint32_t ByteRate;
   uint16_t BlockAlign;
   uint16_t BitsPerSample;
 };
 static_assert(sizeof(FmtPcmSubchunk) == 24, "FmtPcmSubchunk size");
 const uint32_t kFmtPcmSubchunkSize =
     sizeof(FmtPcmSubchunk) - sizeof(ChunkHeader);

 // Pack struct to avoid additional padding bytes.
 #pragma pack(2)
 struct FmtIeeeFloatSubchunk {
   ChunkHeader header;
   uint16_t AudioFormat;
   uint16_t NumChannels;
   uint32_t SampleRate;
   uint32_t ByteRate;
   uint16_t BlockAlign;
   uint16_t BitsPerSample;
   uint16_t ExtensionSize;
 };
 static_assert(sizeof(FmtIeeeFloatSubchunk) == 26, "FmtIeeeFloatSubchunk size");
 const uint32_t kFmtIeeeFloatSubchunkSize =
     sizeof(FmtIeeeFloatSubchunk) - sizeof(ChunkHeader);

 // Simple PCM wav header. It does not include chunks that are not essential to
 // read audio samples.
 #pragma pack(2)
 struct WavHeaderPcm {
   WavHeaderPcm(const WavHeaderPcm&) = default;
   WavHeaderPcm& operator=(const WavHeaderPcm&) = default;
   RiffHeader riff;
   FmtPcmSubchunk fmt;
   struct {
     ChunkHeader header;
   } data;
 };
 static_assert(sizeof(WavHeaderPcm) == kPcmWavHeaderSize,
               "no padding in header");

 // IEEE Float Wav header, includes extra chunks necessary for proper non-PCM
 // WAV implementation.
 #pragma pack(2)
 struct WavHeaderIeeeFloat {
   WavHeaderIeeeFloat(const WavHeaderIeeeFloat&) = default;
   WavHeaderIeeeFloat& operator=(const WavHeaderIeeeFloat&) = default;
   RiffHeader riff;
   FmtIeeeFloatSubchunk fmt;
   struct {
     ChunkHeader header;
     uint32_t SampleLength;
   } fact;
   struct {
     ChunkHeader header;
   } data;
 };
 static_assert(sizeof(WavHeaderIeeeFloat) == kIeeeFloatWavHeaderSize,
               "no padding in header");

 uint32_t PackFourCC(char a, char b, char c, char d) {
   uint32_t packed_value =
       static_cast<uint32_t>(a) | static_cast<uint32_t>(b) << 8 |
       static_cast<uint32_t>(c) << 16 | static_cast<uint32_t>(d) << 24;
   return packed_value;
 }

 std::string ReadFourCC(uint32_t x) {
   return std::string(reinterpret_cast<char*>(&x), 4);
 }

 uint16_t MapWavFormatToHeaderField(WavFormat format) {
   switch (format) {
     case WavFormat::kWavFormatPcm:
       return 1;
     case WavFormat::kWavFormatIeeeFloat:
       return 3;
     case WavFormat::kWavFormatALaw:
       return 6;
     case WavFormat::kWavFormatMuLaw:
       return 7;
   }
   RTC_CHECK(false);
 }

 WavFormat MapHeaderFieldToWavFormat(uint16_t format_header_value) {
   if (format_header_value == 1) {
     return WavFormat::kWavFormatPcm;
   }
   if (format_header_value == 3) {
     return WavFormat::kWavFormatIeeeFloat;
   }

   RTC_CHECK(false) << "Unsupported WAV format";
 }

 uint32_t RiffChunkSize(size_t bytes_in_payload, size_t header_size) {
   return static_cast<uint32_t>(bytes_in_payload + header_size -
                                sizeof(ChunkHeader));
 }

 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);
 }

 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,
                    WavHeaderReader* 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)) !=
         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(FmtPcmSubchunk* fmt_subchunk, WavHeaderReader* readable) {
   // Reads "fmt " chunk payload.
   if (readable->Read(&(fmt_subchunk->AudioFormat), kFmtPcmSubchunkSize) !=
       kFmtPcmSubchunkSize)
     return false;
   const uint32_t fmt_size = fmt_subchunk->header.Size;
   if (fmt_size != kFmtPcmSubchunkSize) {
     // There is an optional two-byte extension field permitted to be present
     // with PCM, but which must be zero.
     int16_t ext_size;
     if (kFmtPcmSubchunkSize + 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;
 }

 void WritePcmWavHeader(size_t num_channels,
                        int sample_rate,
                        size_t bytes_per_sample,
                        size_t num_samples,
                        uint8_t* buf,
                        size_t* header_size) {
   RTC_CHECK(buf);
   RTC_CHECK(header_size);
   *header_size = kPcmWavHeaderSize;
   auto header = rtc::MsanUninitialized<WavHeaderPcm>({});
   const size_t bytes_in_payload = bytes_per_sample * num_samples;

   header.riff.header.ID = PackFourCC('R', 'I', 'F', 'F');
   header.riff.header.Size = RiffChunkSize(bytes_in_payload, *header_size);
   header.riff.Format = PackFourCC('W', 'A', 'V', 'E');
   header.fmt.header.ID = PackFourCC('f', 'm', 't', ' ');
   header.fmt.header.Size = kFmtPcmSubchunkSize;
   header.fmt.AudioFormat = MapWavFormatToHeaderField(WavFormat::kWavFormatPcm);
   header.fmt.NumChannels = static_cast<uint16_t>(num_channels);
   header.fmt.SampleRate = sample_rate;
   header.fmt.ByteRate = ByteRate(num_channels, sample_rate, bytes_per_sample);
   header.fmt.BlockAlign = BlockAlign(num_channels, bytes_per_sample);
   header.fmt.BitsPerSample = static_cast<uint16_t>(8 * bytes_per_sample);
   header.data.header.ID = PackFourCC('d', 'a', 't', 'a');
   header.data.header.Size = 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, *header_size);
 }

 void WriteIeeeFloatWavHeader(size_t num_channels,
                              int sample_rate,
                              size_t bytes_per_sample,
                              size_t num_samples,
                              uint8_t* buf,
                              size_t* header_size) {
   RTC_CHECK(buf);
   RTC_CHECK(header_size);
   *header_size = kIeeeFloatWavHeaderSize;
   auto header = rtc::MsanUninitialized<WavHeaderIeeeFloat>({});
   const size_t bytes_in_payload = bytes_per_sample * num_samples;

   header.riff.header.ID = PackFourCC('R', 'I', 'F', 'F');
   header.riff.header.Size = RiffChunkSize(bytes_in_payload, *header_size);
   header.riff.Format = PackFourCC('W', 'A', 'V', 'E');
   header.fmt.header.ID = PackFourCC('f', 'm', 't', ' ');
   header.fmt.header.Size = kFmtIeeeFloatSubchunkSize;
   header.fmt.AudioFormat =
       MapWavFormatToHeaderField(WavFormat::kWavFormatIeeeFloat);
   header.fmt.NumChannels = static_cast<uint16_t>(num_channels);
   header.fmt.SampleRate = sample_rate;
   header.fmt.ByteRate = ByteRate(num_channels, sample_rate, bytes_per_sample);
   header.fmt.BlockAlign = BlockAlign(num_channels, bytes_per_sample);
   header.fmt.BitsPerSample = static_cast<uint16_t>(8 * bytes_per_sample);
   header.fmt.ExtensionSize = 0;
   header.fact.header.ID = PackFourCC('f', 'a', 'c', 't');
   header.fact.header.Size = 4;
   header.fact.SampleLength = static_cast<uint32_t>(num_channels * num_samples);
   header.data.header.ID = PackFourCC('d', 'a', 't', 'a');
   header.data.header.Size = 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, *header_size);
 }

 // Returns the number of bytes per sample for the format.
 size_t GetFormatBytesPerSample(WavFormat format) {
   switch (format) {
     case WavFormat::kWavFormatPcm:
       // Other values may be OK, but for now we're conservative.
       return 2;
     case WavFormat::kWavFormatALaw:
     case WavFormat::kWavFormatMuLaw:
       return 1;
     case WavFormat::kWavFormatIeeeFloat:
       return 4;
     default:
       RTC_CHECK(false);
       return 2;
   }
 }

 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 >
       std::numeric_limits<uint16_t>::max())
     return false;
   if (static_cast<uint64_t>(sample_rate) * num_channels * bytes_per_sample >
       std::numeric_limits<uint32_t>::max())
     return false;

   // format and bytes_per_sample must agree.
   switch (format) {
     case WavFormat::kWavFormatPcm:
       // Other values may be OK, but for now we're conservative:
       if (bytes_per_sample != 1 && bytes_per_sample != 2)
         return false;
       break;
     case WavFormat::kWavFormatALaw:
     case WavFormat::kWavFormatMuLaw:
       if (bytes_per_sample != 1)
         return false;
       break;
     case WavFormat::kWavFormatIeeeFloat:
       if (bytes_per_sample != 4)
         return false;
       break;
     default:
       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 = kPcmWavHeaderSize - 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;
 }

 }  // namespace

 bool CheckWavParameters(size_t num_channels,
                         int sample_rate,
                         WavFormat format,
                         size_t num_samples) {
   return CheckWavParameters(num_channels, sample_rate, format,
                             GetFormatBytesPerSample(format), num_samples);
 }

 void WriteWavHeader(size_t num_channels,
                     int sample_rate,
                     WavFormat format,
                     size_t num_samples,
                     uint8_t* buf,
                     size_t* header_size) {
   RTC_CHECK(buf);
   RTC_CHECK(header_size);

   const size_t bytes_per_sample = GetFormatBytesPerSample(format);
   RTC_CHECK(CheckWavParameters(num_channels, sample_rate, format,
                                bytes_per_sample, num_samples));
   if (format == WavFormat::kWavFormatPcm) {
     WritePcmWavHeader(num_channels, sample_rate, bytes_per_sample, num_samples,
                       buf, header_size);
   } else {
     RTC_CHECK_EQ(format, WavFormat::kWavFormatIeeeFloat);
     WriteIeeeFloatWavHeader(num_channels, sample_rate, bytes_per_sample,
                             num_samples, buf, header_size);
   }
 }

 bool ReadWavHeader(WavHeaderReader* readable,
                    size_t* num_channels,
                    int* sample_rate,
                    WavFormat* format,
                    size_t* bytes_per_sample,
                    size_t* num_samples,
                    int64_t* data_start_pos) {
   // Read using the PCM header, even though it might be float Wav file
   auto header = rtc::MsanUninitialized<WavHeaderPcm>({});

   // 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(&header.data.header, readable, "data")) {
     RTC_LOG(LS_ERROR) << "Cannot find 'data' chunk.";
     return false;
   }

   // Parse needed fields.
   *format = MapHeaderFieldToWavFormat(header.fmt.AudioFormat);
   *num_channels = header.fmt.NumChannels;
   *sample_rate = header.fmt.SampleRate;
   *bytes_per_sample = header.fmt.BitsPerSample / 8;
   const size_t bytes_in_payload = header.data.header.Size;
   if (*bytes_per_sample == 0)
     return false;
   *num_samples = bytes_in_payload / *bytes_per_sample;

   const size_t header_size = *format == WavFormat::kWavFormatPcm
                                  ? kPcmWavHeaderSize
                                  : kIeeeFloatWavHeaderSize;

   if (header.riff.header.Size < RiffChunkSize(bytes_in_payload, header_size))
     return false;
   if (header.fmt.ByteRate !=
       ByteRate(*num_channels, *sample_rate, *bytes_per_sample))
     return false;
   if (header.fmt.BlockAlign != BlockAlign(*num_channels, *bytes_per_sample))
     return false;

   if (!CheckWavParameters(*num_channels, *sample_rate, *format,
                           *bytes_per_sample, *num_samples)) {
     return false;
   }

   *data_start_pos = readable->GetPosition();
   return true;
 }

 }  // namespace webrtc
	/*
	* 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
	// https://ccrma.stanford.edu/courses/422/projects/WaveFormat/ and
	// http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html

	#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 {

	#ifndef WEBRTC_ARCH_LITTLE_ENDIAN
	#error "Code not working properly for big endian platforms."
	#endif

	#pragma pack(2)
	struct ChunkHeader {
	uint32_t ID;
	uint32_t Size;
	};
	static_assert(sizeof(ChunkHeader) == 8, "ChunkHeader size");

	#pragma pack(2)
	struct RiffHeader {
	ChunkHeader header;
	uint32_t Format;
	};
	static_assert(sizeof(RiffHeader) == sizeof(ChunkHeader) + 4, "RiffHeader size");

	// We can't nest this definition in WavHeader, because VS2013 gives an error
	// on sizeof(WavHeader::fmt): "error C2070: 'unknown': illegal sizeof operand".
	#pragma pack(2)
	struct FmtPcmSubchunk {
	ChunkHeader header;
	uint16_t AudioFormat;
	uint16_t NumChannels;
	uint32_t SampleRate;
	uint32_t ByteRate;
	uint16_t BlockAlign;
	uint16_t BitsPerSample;
	};
	static_assert(sizeof(FmtPcmSubchunk) == 24, "FmtPcmSubchunk size");
	const uint32_t kFmtPcmSubchunkSize =
	sizeof(FmtPcmSubchunk) - sizeof(ChunkHeader);

	// Pack struct to avoid additional padding bytes.
	#pragma pack(2)
	struct FmtIeeeFloatSubchunk {
	ChunkHeader header;
	uint16_t AudioFormat;
	uint16_t NumChannels;
	uint32_t SampleRate;
	uint32_t ByteRate;
	uint16_t BlockAlign;
	uint16_t BitsPerSample;
	uint16_t ExtensionSize;
	};
	static_assert(sizeof(FmtIeeeFloatSubchunk) == 26, "FmtIeeeFloatSubchunk size");
	const uint32_t kFmtIeeeFloatSubchunkSize =
	sizeof(FmtIeeeFloatSubchunk) - sizeof(ChunkHeader);

	// Simple PCM wav header. It does not include chunks that are not essential to
	// read audio samples.
	#pragma pack(2)
	struct WavHeaderPcm {
	WavHeaderPcm(const WavHeaderPcm&) = default;
	WavHeaderPcm& operator=(const WavHeaderPcm&) = default;
	RiffHeader riff;
	FmtPcmSubchunk fmt;
	struct {
	ChunkHeader header;
	} data;
	};
	static_assert(sizeof(WavHeaderPcm) == kPcmWavHeaderSize,
	"no padding in header");

	// IEEE Float Wav header, includes extra chunks necessary for proper non-PCM
	// WAV implementation.
	#pragma pack(2)
	struct WavHeaderIeeeFloat {
	WavHeaderIeeeFloat(const WavHeaderIeeeFloat&) = default;
	WavHeaderIeeeFloat& operator=(const WavHeaderIeeeFloat&) = default;
	RiffHeader riff;
	FmtIeeeFloatSubchunk fmt;
	struct {
	ChunkHeader header;
	uint32_t SampleLength;
	} fact;
	struct {
	ChunkHeader header;
	} data;
	};
	static_assert(sizeof(WavHeaderIeeeFloat) == kIeeeFloatWavHeaderSize,
	"no padding in header");

	uint32_t PackFourCC(char a, char b, char c, char d) {
	uint32_t packed_value =
	static_cast<uint32_t>(a) \| static_cast<uint32_t>(b) << 8 \|
	static_cast<uint32_t>(c) << 16 \| static_cast<uint32_t>(d) << 24;
	return packed_value;
	}

	std::string ReadFourCC(uint32_t x) {
	return std::string(reinterpret_cast<char*>(&x), 4);
	}

	uint16_t MapWavFormatToHeaderField(WavFormat format) {
	switch (format) {
	case WavFormat::kWavFormatPcm:
	return 1;
	case WavFormat::kWavFormatIeeeFloat:
	return 3;
	case WavFormat::kWavFormatALaw:
	return 6;
	case WavFormat::kWavFormatMuLaw:
	return 7;
	}
	RTC_CHECK(false);
	}

	WavFormat MapHeaderFieldToWavFormat(uint16_t format_header_value) {
	if (format_header_value == 1) {
	return WavFormat::kWavFormatPcm;
	}
	if (format_header_value == 3) {
	return WavFormat::kWavFormatIeeeFloat;
	}

	RTC_CHECK(false) << "Unsupported WAV format";
	}

	uint32_t RiffChunkSize(size_t bytes_in_payload, size_t header_size) {
	return static_cast<uint32_t>(bytes_in_payload + header_size -
	sizeof(ChunkHeader));
	}

	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);
	}

	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,
	WavHeaderReader* 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)) !=
	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(FmtPcmSubchunk* fmt_subchunk, WavHeaderReader* readable) {
	// Reads "fmt " chunk payload.
	if (readable->Read(&(fmt_subchunk->AudioFormat), kFmtPcmSubchunkSize) !=
	kFmtPcmSubchunkSize)
	return false;
	const uint32_t fmt_size = fmt_subchunk->header.Size;
	if (fmt_size != kFmtPcmSubchunkSize) {
	// There is an optional two-byte extension field permitted to be present
	// with PCM, but which must be zero.
	int16_t ext_size;
	if (kFmtPcmSubchunkSize + 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;
	}

	void WritePcmWavHeader(size_t num_channels,
	int sample_rate,
	size_t bytes_per_sample,
	size_t num_samples,
	uint8_t* buf,
	size_t* header_size) {
	RTC_CHECK(buf);
	RTC_CHECK(header_size);
	*header_size = kPcmWavHeaderSize;
	auto header = rtc::MsanUninitialized<WavHeaderPcm>({});
	const size_t bytes_in_payload = bytes_per_sample * num_samples;

	header.riff.header.ID = PackFourCC('R', 'I', 'F', 'F');
	header.riff.header.Size = RiffChunkSize(bytes_in_payload, *header_size);
	header.riff.Format = PackFourCC('W', 'A', 'V', 'E');
	header.fmt.header.ID = PackFourCC('f', 'm', 't', ' ');
	header.fmt.header.Size = kFmtPcmSubchunkSize;
	header.fmt.AudioFormat = MapWavFormatToHeaderField(WavFormat::kWavFormatPcm);
	header.fmt.NumChannels = static_cast<uint16_t>(num_channels);
	header.fmt.SampleRate = sample_rate;
	header.fmt.ByteRate = ByteRate(num_channels, sample_rate, bytes_per_sample);
	header.fmt.BlockAlign = BlockAlign(num_channels, bytes_per_sample);
	header.fmt.BitsPerSample = static_cast<uint16_t>(8 * bytes_per_sample);
	header.data.header.ID = PackFourCC('d', 'a', 't', 'a');
	header.data.header.Size = 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, *header_size);
	}

	void WriteIeeeFloatWavHeader(size_t num_channels,
	int sample_rate,
	size_t bytes_per_sample,
	size_t num_samples,
	uint8_t* buf,
	size_t* header_size) {
	RTC_CHECK(buf);
	RTC_CHECK(header_size);
	*header_size = kIeeeFloatWavHeaderSize;
	auto header = rtc::MsanUninitialized<WavHeaderIeeeFloat>({});
	const size_t bytes_in_payload = bytes_per_sample * num_samples;

	header.riff.header.ID = PackFourCC('R', 'I', 'F', 'F');
	header.riff.header.Size = RiffChunkSize(bytes_in_payload, *header_size);
	header.riff.Format = PackFourCC('W', 'A', 'V', 'E');
	header.fmt.header.ID = PackFourCC('f', 'm', 't', ' ');
	header.fmt.header.Size = kFmtIeeeFloatSubchunkSize;
	header.fmt.AudioFormat =
	MapWavFormatToHeaderField(WavFormat::kWavFormatIeeeFloat);
	header.fmt.NumChannels = static_cast<uint16_t>(num_channels);
	header.fmt.SampleRate = sample_rate;
	header.fmt.ByteRate = ByteRate(num_channels, sample_rate, bytes_per_sample);
	header.fmt.BlockAlign = BlockAlign(num_channels, bytes_per_sample);
	header.fmt.BitsPerSample = static_cast<uint16_t>(8 * bytes_per_sample);
	header.fmt.ExtensionSize = 0;
	header.fact.header.ID = PackFourCC('f', 'a', 'c', 't');
	header.fact.header.Size = 4;
	header.fact.SampleLength = static_cast<uint32_t>(num_channels * num_samples);
	header.data.header.ID = PackFourCC('d', 'a', 't', 'a');
	header.data.header.Size = 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, *header_size);
	}

	// Returns the number of bytes per sample for the format.
	size_t GetFormatBytesPerSample(WavFormat format) {
	switch (format) {
	case WavFormat::kWavFormatPcm:
	// Other values may be OK, but for now we're conservative.
	return 2;
	case WavFormat::kWavFormatALaw:
	case WavFormat::kWavFormatMuLaw:
	return 1;
	case WavFormat::kWavFormatIeeeFloat:
	return 4;
	default:
	RTC_CHECK(false);
	return 2;
	}
	}

	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 >
	std::numeric_limits<uint16_t>::max())
	return false;
	if (static_cast<uint64_t>(sample_rate) * num_channels * bytes_per_sample >
	std::numeric_limits<uint32_t>::max())
	return false;

	// format and bytes_per_sample must agree.
	switch (format) {
	case WavFormat::kWavFormatPcm:
	// Other values may be OK, but for now we're conservative:
	if (bytes_per_sample != 1 && bytes_per_sample != 2)
	return false;
	break;
	case WavFormat::kWavFormatALaw:
	case WavFormat::kWavFormatMuLaw:
	if (bytes_per_sample != 1)
	return false;
	break;
	case WavFormat::kWavFormatIeeeFloat:
	if (bytes_per_sample != 4)
	return false;
	break;
	default:
	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 = kPcmWavHeaderSize - 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;
	}

	} // namespace

	bool CheckWavParameters(size_t num_channels,
	int sample_rate,
	WavFormat format,
	size_t num_samples) {
	return CheckWavParameters(num_channels, sample_rate, format,
	GetFormatBytesPerSample(format), num_samples);
	}

	void WriteWavHeader(size_t num_channels,
	int sample_rate,
	WavFormat format,
	size_t num_samples,
	uint8_t* buf,
	size_t* header_size) {
	RTC_CHECK(buf);
	RTC_CHECK(header_size);

	const size_t bytes_per_sample = GetFormatBytesPerSample(format);
	RTC_CHECK(CheckWavParameters(num_channels, sample_rate, format,
	bytes_per_sample, num_samples));
	if (format == WavFormat::kWavFormatPcm) {
	WritePcmWavHeader(num_channels, sample_rate, bytes_per_sample, num_samples,
	buf, header_size);
	} else {
	RTC_CHECK_EQ(format, WavFormat::kWavFormatIeeeFloat);
	WriteIeeeFloatWavHeader(num_channels, sample_rate, bytes_per_sample,
	num_samples, buf, header_size);
	}
	}

	bool ReadWavHeader(WavHeaderReader* readable,
	size_t* num_channels,
	int* sample_rate,
	WavFormat* format,
	size_t* bytes_per_sample,
	size_t* num_samples,
	int64_t* data_start_pos) {
	// Read using the PCM header, even though it might be float Wav file
	auto header = rtc::MsanUninitialized<WavHeaderPcm>({});

	// 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(&header.data.header, readable, "data")) {
	RTC_LOG(LS_ERROR) << "Cannot find 'data' chunk.";
	return false;
	}

	// Parse needed fields.
	*format = MapHeaderFieldToWavFormat(header.fmt.AudioFormat);
	*num_channels = header.fmt.NumChannels;
	*sample_rate = header.fmt.SampleRate;
	*bytes_per_sample = header.fmt.BitsPerSample / 8;
	const size_t bytes_in_payload = header.data.header.Size;
	if (*bytes_per_sample == 0)
	return false;
	num_samples = bytes_in_payload / bytes_per_sample;

	const size_t header_size = *format == WavFormat::kWavFormatPcm
	? kPcmWavHeaderSize
	: kIeeeFloatWavHeaderSize;

	if (header.riff.header.Size < RiffChunkSize(bytes_in_payload, header_size))
	return false;
	if (header.fmt.ByteRate !=
	ByteRate(num_channels, sample_rate, *bytes_per_sample))
	return false;
	if (header.fmt.BlockAlign != BlockAlign(num_channels, bytes_per_sample))
	return false;

	if (!CheckWavParameters(num_channels, sample_rate, *format,
	bytes_per_sample, num_samples)) {
	return false;
	}

	*data_start_pos = readable->GetPosition();
	return true;
	}

	} // namespace webrtc