public void Initialize(Stream stream)
{
Contract.Ensures(_reader != null);
Contract.Ensures(_reader.BaseStream == stream);
Contract.Ensures(_channels > 0);
Contract.Ensures(_samplesRemaining >= 0);
Contract.Ensures(_bytesPerSample > 0);
Contract.Ensures(_divisor > 0);
_reader = new RiffReader(stream);
if (!_reader.Validate() || _reader.ReadFourCC() != "WAVE")
{
throw new UnsupportedAudioException(Resources.SampleDecoderNotWaveError);
}
uint fmtChunkSize = _reader.SeekToChunk("fmt ");
if (fmtChunkSize == 0)
{
throw new IOException(Resources.SampleDecoderMissingFmtError);
}
if (fmtChunkSize < 16)
{
throw new IOException(Resources.SampleDecoderFmtLengthError);
}
var format = (Format)_reader.ReadUInt16();
if (format != Format.Pcm && format != Format.Extensible)
{
throw new UnsupportedAudioException(Resources.SampleDecoderUnsupportedError);
}
// WAVEFORMATEXTENSIBLE headers are 40 bytes long:
if (format == Format.Extensible && fmtChunkSize < 40)
{
throw new IOException(Resources.SampleDecoderFmtLengthError);
}
_channels = _reader.ReadUInt16();
if (_channels == 0 || _channels > 2)
{
throw new UnsupportedAudioException(Resources.SampleDecoderChannelsError);
}
// Ignore sampleRate and bytesPerSecond:
stream.Seek(8, SeekOrigin.Current);
ushort blockAlign = _reader.ReadUInt16();
uint bitsPerSample = _reader.ReadUInt16();
// Read the WAVEFORMATEXTENSIBLE extended header, if present:
if (format == Format.Extensible)
{
if (_reader.ReadUInt16() < 22)
{
throw new UnsupportedAudioException(Resources.SampleDecoderFmtExtensionLengthError);
}
if (bitsPerSample % 8 != 0)
{
throw new UnsupportedAudioException(Resources.SampleDecoderBitsPerSampleError);
}
bitsPerSample = _reader.ReadUInt16();
// Ignore the channel mask for now:
stream.Seek(4, SeekOrigin.Current);
if ((Format)_reader.ReadUInt16() != Format.Pcm)
{
throw new UnsupportedAudioException(Resources.SampleDecoderUnsupportedError);
}
}
_bytesPerSample = (int)Math.Ceiling(bitsPerSample / (double)8);
_divisor = (float)Math.Pow(2, bitsPerSample - 1);
uint dataChunkSize = _reader.SeekToChunk("data");
if (dataChunkSize == 0)
{
_samplesRemaining = 0;
}
else
{
_samplesRemaining = dataChunkSize / blockAlign;
}
}
public AudioInfo ReadAudioInfo(Stream stream)
{
Contract.Ensures(stream.CanRead);
Contract.Ensures(stream.CanSeek);
Contract.Ensures(Contract.Result <AudioInfo>() != null);
if (stream.Length < 45) // 12 byte RIFF descriptor + 24 byte fmt chunk + 9 byte data chunk
{
throw new IOException(Resources.AudioInfoDecoderLengthError);
}
using (var reader = new RiffReader(stream))
{
if (!reader.Validate() || reader.ReadFourCC() != "WAVE")
{
throw new UnsupportedAudioException(Resources.AudioInfoDecoderNotWaveError);
}
uint fmtChunkSize = reader.SeekToChunk("fmt ");
if (fmtChunkSize == 0)
{
throw new IOException(Resources.AudioInfoDecoderMissingFmtError);
}
if (fmtChunkSize < 16)
{
throw new IOException(Resources.AudioInfoDecoderFmtLengthError);
}
var format = (Format)reader.ReadUInt16();
if (format != Format.Pcm && format != Format.Extensible)
{
throw new UnsupportedAudioException(Resources.AudioInfoDecoderUnsupportedError);
}
// WAVEFORMATEXTENSIBLE headers are 40 bytes long:
if (format == Format.Extensible && fmtChunkSize < 40)
{
throw new IOException(Resources.AudioInfoDecoderFmtLengthError);
}
ushort channels = reader.ReadUInt16();
uint sampleRate = reader.ReadUInt32();
stream.Seek(4, SeekOrigin.Current); // Ignore bytesPerSecond
ushort blockAlign = reader.ReadUInt16();
uint bitsPerSample = reader.ReadUInt16();
// Read the WAVEFORMATEXTENSIBLE extended header, if present:
if (format == Format.Extensible)
{
if (reader.ReadUInt16() < 22)
{
throw new UnsupportedAudioException(Resources.AudioInfoDecoderFmtExtensionLengthError);
}
if (bitsPerSample % 8 != 0)
{
throw new UnsupportedAudioException(Resources.AudioInfoDecoderBitsPerSampleError);
}
bitsPerSample = reader.ReadUInt16();
// Ignore the channel mask for now:
stream.Seek(4, SeekOrigin.Current);
if ((Format)reader.ReadUInt16() != Format.Pcm)
{
throw new UnsupportedAudioException(Resources.AudioInfoDecoderUnsupportedError);
}
}
uint dataChunkSize = reader.SeekToChunk("data");
if (dataChunkSize == 0)
{
throw new IOException(Resources.AudioInfoDecoderMissingSamplesError);
}
return(new AudioInfo("LPCM", channels, (int)bitsPerSample, (int)sampleRate, dataChunkSize / blockAlign));
}
}
