using System;

using System.Diagnostics;

using System.IO;

namespace Spectrogram

{

[Obsolete("Use a library like NAudio to extract data from WAV files (see spectrogram quickstart for examples)", true)]

public static class WavFile

{

private static (string id, uint length) ChunkInfo(BinaryReader br, long position)

{

br.BaseStream.Seek(position, SeekOrigin.Begin);

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

uint chunkBytes = br.ReadUInt32();

return (chunkID, chunkBytes);

}

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))

{

// The first chunk is RIFF section

// Length should be the number of bytes in the file minus 4

var (id, length) = ChunkInfo(br, 0);

Console.WriteLine($"First chunk '{id}' indicates {length:N0} bytes");

if (id != "RIFF")

throw new InvalidOperationException($"Unsupported WAV format (first chunk ID was '{id}', not 'RIFF')");

// The second chunk is FORMAT section

var fmtChunk = ChunkInfo(br, 12);

Console.WriteLine($"Format chunk '{fmtChunk.id}' indicates {fmtChunk.length:N0} bytes");

if (fmtChunk.id != "fmt ")

throw new InvalidOperationException($"Unsupported WAV format (first chunk ID was '{fmtChunk.id}', not 'fmt ')");

if (fmtChunk.length != 16)

throw new InvalidOperationException($"Unsupported WAV format (expect 16 byte 'fmt' chunk, got {fmtChunk.length} bytes)");

// By now we verified this is probably a valid FORMAT section, so read its values.

int audioFormat = br.ReadUInt16();

Console.WriteLine($"audio format: {audioFormat}");

if (audioFormat != 1)

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

int channelCount = br.ReadUInt16();

Console.WriteLine($"channel count: {channelCount}");

if (channelCount < 0 || channelCount > 2)

throw new NotImplementedException($"Unsupported WAV format (must be 1 or 2 channel, file has {channelCount})");

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

Console.WriteLine($"sample rate: {sampleRate} Hz");

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

Console.WriteLine($"byteRate: {byteRate}");

ushort blockSize = br.ReadUInt16();

Console.WriteLine($"block size: {blockSize} bytes per sample");

ushort bitsPerSample = br.ReadUInt16();

Console.WriteLine($"resolution: {bitsPerSample}-bit");

if (bitsPerSample != 16)

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

// Cycle custom chunks until we get to the DATA chunk

// Various chunks may exist until the data chunk appears

long nextChunkPosition = 36;

int maximumChunkNumber = 42;

long firstDataByte = 0;

long dataByteCount = 0;

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

{

var chunk = ChunkInfo(br, nextChunkPosition);

Console.WriteLine($"Chunk at {nextChunkPosition} ('{chunk.id}') indicates {chunk.length:N0} bytes");

if (chunk.id == "data")

{

firstDataByte = nextChunkPosition + 8;

dataByteCount = chunk.length;

break;

}

nextChunkPosition += chunk.length + 8;

}

if (firstDataByte == 0 || dataByteCount == 0)

throw new InvalidOperationException("Unsupported WAV format (no 'data' chunk found)");

Console.WriteLine($"PCM data starts at {firstDataByte} and contains {dataByteCount} bytes");

// Now read PCM data values into an array and return it

long sampleCount = dataByteCount / blockSize;

Debug.WriteLine($"Samples in file: {sampleCount}");

double[] L = null;

double[] R = null;

if (channelCount == 1)

{

L = new double[sampleCount];

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

{

L[i] = br.ReadInt16();

}

}

else if (channelCount == 2)

{

L = new double[sampleCount];

R = new double[sampleCount];

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

{

L[i] = br.ReadInt16();

R[i] = br.ReadInt16();

}

}

return (sampleRate, L, R);

}

}

}

}