private void ParseRiff(Stream st)
{
// Whenever parse the RIFF, reset everything.
Init();
// The first three blocks do not follow the rest.
// (WAVE is not followed by size, and there is no hard definition of "WAVEfmt " are always together)
// The smallest wave is 44 bytes.
Sanity.Requires(st.Length >= 44, $"The stream length {st.Length} is too short, should be at least 44.");
// For safety, 2G file will not be supported.
Sanity.Requires(st.Length <= int.MaxValue, $"The stream length {st.Length} is too long, at most 2G.");
// 0-3: RIFF.
st.Read(ChunkNameBytes, 0, 4);
Sanity.Requires(GetName() == "RIFF", "Invalid header, should be RIFF.");
// 4-7: int 32 for RIFF size.
st.Read(Int32Bytes, 0, 4);
Sanity.Requires(GetInt32() + 8 == st.Length, "Stream length mismatch, in RIFF chunk.");
// 8-11: WAVE.
st.Read(ChunkNameBytes, 0, 4);
Sanity.Requires(GetName() == "WAVE", "Invalid header, should be WAVE");
// Clear the format chunk and data chunk.
FormatChunk = InitEmptyChunk();
DataChunk = InitEmptyChunk();
// Recursively parse the remaining chunks.
ParseChunks(st);
// Validate the rest values.
PostCheck(st);
}
private void ParseRecursively(Stream st)
{
if (st.Position == st.Length)
{
return;
}
Sanity.Requires(st.Position + 8 <= st.Length, $"Audio length too short, at 0x{st.Position:x}.");
string chunkName = st.ReadBytesToString(4, Encoding.ASCII);
int chunkSize = st.ReadBytesToInt32();
Chunk chunk = new Chunk {
Name = chunkName, Size = chunkSize, Offset = (int)st.Position
};
switch (chunkName)
{
case "fmt ":
Sanity.Requires(FormatChunk.Name != "", "Dupelicate format chunk.");
FormatChunk = chunk;
return;
case "data":
Sanity.Requires(DataChunk.Name != "", "Duplicate data chunk.");
DataChunk = chunk;
return;
default:
break;
}
Sanity.Requires(st.Position + chunkSize <= st.Length, $"Audio length too short, at {chunkName}, at 0x{st.Position:x}.");
st.Seek(chunkSize, SeekOrigin.Current);
ParseRecursively(st);
}
private void ParseHeader(Stream st)
{
Sanity.Requires(st.Length >= 44, $"Audio size is too small. Expected at least 44, which is actually {st.Length} ");
Sanity.Requires(st.Length <= int.MaxValue, $"Audio size is too large, more than 2GB.");
Sanity.Requires(st.ReadBytesToString(4, Encoding.ASCII) == "RIFF", $"File type error, not RIFF.");
Sanity.Requires(st.ReadBytesToInt32() + 8 == st.Length, $"File length error, in RIFF chunk.");
Sanity.Requires(st.ReadBytesToString(4, Encoding.ASCII) == "WAVE", $"File type error, not WAVE");
}
/// <summary>
/// Shallow parse the audio from a certain path.
/// </summary>
/// <param name="filePath">The path of the audio file.</param>
public void ShallowParse(string filePath)
{
Sanity.Requires(File.Exists(filePath), $"File not exist: {filePath}.");
using (FileStream st = new FileStream(filePath, FileMode.Open, FileAccess.Read))
{
// Call the shallow parse stream to keep the core algorithm identical.
ShallowParse(st);
}
}
private void CheckData(Stream st)
{
Sanity.Requires(DataChunk.Name != "", "No data chunk.");
if (IsDeep)
{
DataBytes = new byte[DataChunk.Size];
st.Seek(DataChunk.Offset, 0);
st.Read(DataBytes, 0, DataChunk.Size);
}
}
private void PostCheck(Stream st)
{
// The format chunk and data chunk have to exist.
Sanity.Requires(FormatChunk.ChunkName != null, "Format error, missing format chunk.");
Sanity.Requires(DataChunk.ChunkName != null, "Format error, missing data chunk.");
// Go to the format chunk.
st.Seek(FormatChunk.ChunkOffset + 8, SeekOrigin.Begin);
// First two bytes for wave type.
st.Read(Int16Bytes, 0, 2);
TypeId = GetInt16();
// Following two bytes for the number of channels.
st.Read(Int16Bytes, 0, 2);
NumChannels = GetInt16();
Sanity.Requires(NumChannels != 0, "Channel cannot be zero.");
// Following four bytes for the sample rate.
st.Read(Int32Bytes, 0, 4);
SampleRate = GetInt32();
Sanity.Requires(SampleRate != 0, "Sample rate cannot be zeror.");
// Following four bytes for the byte rate(bytes per second).
// Audio length(seconds) can be calculated by this value and the length of data bytes directly.
st.Read(Int32Bytes, 0, 4);
ByteRate = GetInt32();
Sanity.Requires(ByteRate != 0, "Byte rate cannot be zero.");
AudioTime = (double)DataChunk.ChunkLength / ByteRate;
// Block align, how many bytes for every "block", e.g. a single sample from all channels.
st.Read(Int16Bytes, 0, 2);
BlockAlign = GetInt16();
Sanity.Requires(BlockAlign != 0, "Block align cannot be zero.");
// Bits per sample, the audio precision, e.g. 8 bit or 16 bit.
st.Read(Int16Bytes, 0, 2);
BitsPerSample = GetInt16();
Sanity.Requires(BitsPerSample != 0, "Bits per sample cannot be zero.");
// The values of all the wave format are redundant, two extra equations should be followed.
Sanity.Requires(ByteRate == BitsPerSample / 8 * SampleRate * NumChannels, "Error in byte rate equation.");
Sanity.Requires(BlockAlign == BitsPerSample / 8 * NumChannels, "Error in block align equation.");
// In practical, invalid format is seldom seen.
// So just let it be.
// Set the wave type string.
SetWaveType();
}
private void CheckFormat(Stream st)
{
Sanity.Requires(FormatChunk.Name != "", "No format chunk.");
Sanity.Requires(FormatChunk.Size >= 16, $"Format chunk too small. Expected at least 16, which is actually {FormatChunk.Size}.");
st.Seek(FormatChunk.Offset, SeekOrigin.Begin);
WaveTypeId = st.ReadBytesToInt16();
NumChannels = st.ReadBytesToInt16();
SampleRate = st.ReadBytesToInt32();
ByteRate = st.ReadBytesToInt32();
BlockAlign = st.ReadBytesToInt16();
BitsPerSample = st.ReadBytesToInt16();
Sanity.Requires(ByteRate == SampleRate * BlockAlign, $"Wave format error: byte rate: {ByteRate}, sample rate: {SampleRate}, block align: {BlockAlign}.");
Sanity.Requires(BitsPerSample * NumChannels == 8 * BlockAlign, $"Wave format error: bits per sample: {BitsPerSample}, channel: {NumChannels}, block align: {BlockAlign}.");
AudioLength = (double)DataChunk.Size / ByteRate;
}
private void ParseChunks(Stream st)
{
// When reaches the end, stop.
if (st.Position == st.Length)
{
return;
}
// If it is a valid chunk, it has to be at least 8
Sanity.Requires(st.Position + 8 <= st.Length, $"Stream length mismatch, at position {st.Position}.");
// Offset is the current position.
int offset = (int)st.Position;
// The first four bytes(of the 8 bytes) is the name.
st.Read(ChunkNameBytes, 0, 4);
string name = GetName();
// The next four bytes(of the 8 bytes) is the chunk siz/length.
st.Read(Int32Bytes, 0, 4);
int length = GetInt32();
// The chunk length should not exceed the end of the file.
Sanity.Requires(st.Position + length <= st.Length, $"Stream length mismatch, at position {st.Position}, in chunk {name}.");
// Move forward.
st.Seek(length, SeekOrigin.Current);
// Set the chunk.
WaveChunk chunk = new WaveChunk
{
ChunkName = name,
ChunkLength = length,
ChunkOffset = offset
};
// Format chunk is special.
if (chunk.ChunkName == "fmt ")
{
// There should be only 1 format chunk.
Sanity.Requires(FormatChunk.ChunkName == null, $"Format error, at most 1 format chunk.");
// The smallest format chunk for PCM is 16.
Sanity.Requires(chunk.ChunkLength >= 16, $"Format error, format chunk length {FormatChunk.ChunkLength}, should be at least 16.");
FormatChunk = chunk;
}
// Data chunk is special.
if (chunk.ChunkName == "data")
{
// There should be only 1 data chunk.
// NOTE: I'M NOT SURE ABOUT THIS, THERE IS NOWHERE SAY ONLY 1 DATA CHUNK IS ALLOWED.
// JUST FOR SIMPLE HERE.
Sanity.Requires(DataChunk.ChunkName == null, $"Format error, at most 1 data chunk.");
DataChunk = chunk;
}
// Add this chunk into the list.
ChunkList.Add(chunk);
// Parse the next chunk recursively.
ParseChunks(st);
}
