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/*
* 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 "webrtc/common_audio/wav_header.h"
#include <algorithm>
#include <cstring>
#include <limits>
#include "webrtc/common_audio/include/audio_util.h"
namespace webrtc {
struct ChunkHeader {
uint32_t ID;
uint32_t Size;
};
COMPILE_ASSERT(sizeof(ChunkHeader) == 8, chunk_header_size);
bool CheckWavParameters(int num_channels,
int sample_rate,
WavFormat format,
int bytes_per_sample,
uint32_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 (static_cast<uint64_t>(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 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 kWavFormatALaw:
case kWavFormatMuLaw:
if (bytes_per_sample != 1)
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 uint32_t max_samples =
(std::numeric_limits<uint32_t>::max()
- (kWavHeaderSize - sizeof(ChunkHeader))) /
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;
}
#ifdef WEBRTC_ARCH_LITTLE_ENDIAN
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;
}
#else
#error "Write be-to-le conversion functions"
#endif
void WriteWavHeader(uint8_t* buf,
int num_channels,
int sample_rate,
WavFormat format,
int bytes_per_sample,
uint32_t num_samples) {
assert(CheckWavParameters(num_channels, sample_rate, format,
bytes_per_sample, num_samples));
struct {
struct {
ChunkHeader header;
uint32_t Format;
} riff;
struct {
ChunkHeader header;
uint16_t AudioFormat;
uint16_t NumChannels;
uint32_t SampleRate;
uint32_t ByteRate;
uint16_t BlockAlign;
uint16_t BitsPerSample;
} fmt;
struct {
ChunkHeader header;
} data;
} header;
COMPILE_ASSERT(sizeof(header) == kWavHeaderSize, no_padding_in_header);
const uint32_t bytes_in_payload = bytes_per_sample * num_samples;
WriteFourCC(&header.riff.header.ID, 'R', 'I', 'F', 'F');
WriteLE32(&header.riff.header.Size,
bytes_in_payload + kWavHeaderSize - sizeof(ChunkHeader));
WriteFourCC(&header.riff.Format, 'W', 'A', 'V', 'E');
WriteFourCC(&header.fmt.header.ID, 'f', 'm', 't', ' ');
WriteLE32(&header.fmt.header.Size, sizeof(header.fmt) - sizeof(ChunkHeader));
WriteLE16(&header.fmt.AudioFormat, format);
WriteLE16(&header.fmt.NumChannels, num_channels);
WriteLE32(&header.fmt.SampleRate, sample_rate);
WriteLE32(&header.fmt.ByteRate, (static_cast<uint32_t>(num_channels)
* sample_rate * bytes_per_sample));
WriteLE16(&header.fmt.BlockAlign, num_channels * bytes_per_sample);
WriteLE16(&header.fmt.BitsPerSample, 8 * bytes_per_sample);
WriteFourCC(&header.data.header.ID, 'd', 'a', 't', 'a');
WriteLE32(&header.data.header.Size, 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);
}
} // namespace webrtc
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