// Simple WAV file reader by Scott Harden released under a MIT license

// Format here is based on http://soundfile.sapp.org/doc/WaveFormat/

using System;

using System.IO;

namespace Spectrogram

{

public static class WavFile

{

public static (int sampleRate, double[] L) ReadMono(string filePath)

{

(int sampleRate, double[] L, _) = ReadStereo(filePath);

return (sampleRate, L);

}

public static (int sampleRate, double[] L, double[] R) ReadStereo(string filePath)

{

using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))

using (BinaryReader br = new BinaryReader(fs))

{

// read and verify content of the header

if (new string(br.ReadChars(4)) != "RIFF")

throw new ArgumentException("invalid WAV header (no RIFF)");

uint chunkSize = br.ReadUInt32();

if (new string(br.ReadChars(4)) != "WAVE")

throw new ArgumentException("invalid WAV file (expected 'WAVE' at byte 8)");

string formatString = new string(br.ReadChars(4));

if (formatString != "fmt ")

throw new NotImplementedException("unsupported WAV header (expected 'fmt ' at byte 12)");

int chunkOneSize = (int)br.ReadUInt32();

int firstByteAfterChunk1 = (int)br.BaseStream.Position + chunkOneSize;

if (chunkOneSize != 16)

throw new NotImplementedException("unsupported WAV header (chunk 1 must be 16 bytes in length)");

int audioFormat = br.ReadUInt16();

if (audioFormat != 1)

throw new NotImplementedException("unsupported WAV header (audio format must be 1, indicating uncompressed PCM data)");

int channelCount = br.ReadUInt16();

int sampleRate = (int)br.ReadUInt32();

int byteRate = (int)br.ReadUInt32();

ushort blockSize = br.ReadUInt16();

ushort bitsPerSample = br.ReadUInt16();

if (bitsPerSample != 16)

throw new NotImplementedException("Only 16-bit WAV files are supported");

if (new string(br.ReadChars(4)) != "data")

throw new ArgumentException($"invalid WAV file (expected 'data' at byte {br.BaseStream.Position - 4})");

// read data values from the WAV file

int dataByteCount = (int)br.ReadUInt32();

int timePoints = dataByteCount / blockSize;

if (channelCount == 1)

{

double[] L = new double[timePoints];

for (int i = 0; i < timePoints; i++)

{

L[i] = br.ReadInt16();

}

return (sampleRate, L, null);

}

else if (channelCount == 2)

{

double[] L = new double[timePoints];

double[] R = new double[timePoints];

for (int i = 0; i < timePoints; i++)

{

L[i] = br.ReadInt16();

R[i] = br.ReadInt16();

}

return (sampleRate, L, R);

}

else

{

throw new InvalidOperationException("channel must be 1 or 2");

}

}

}

}

}