public void Initialize(Stream stream)
{
Contract.Ensures(_converter != null);
Contract.Ensures(_magicCookie != IntPtr.Zero);
Contract.Ensures(_divisor > 0);
try
{
var audioFile = new NativeAudioFile(AudioFileType.M4A, stream);
_inputDescription = audioFile.GetProperty <AudioStreamBasicDescription>(AudioFilePropertyId.DataFormat);
if (_inputDescription.AudioFormat != AudioFormat.AppleLossless)
{
throw new UnsupportedAudioException(Resources.LosslessSampleDecoderFormatError);
}
var outputDescription = InitializeOutputDescription(_inputDescription);
_divisor = (float)Math.Pow(2, outputDescription.BitsPerChannel - 1);
_converter = new NativeAudioConverter(ref _inputDescription, ref outputDescription, audioFile);
_magicCookie = InitializeMagicCookie(audioFile, _converter);
}
catch (TypeInitializationException e)
{
if (e.InnerException != null && e.InnerException.GetType() == typeof(ExtensionInitializationException))
{
throw e.InnerException;
}
throw;
}
}
static IntPtr InitializeMagicCookie(NativeAudioFile audioFile, NativeAudioConverter converter)
{
Contract.Requires(audioFile != null);
Contract.Requires(converter != null);
uint dataSize;
uint isWritable;
AudioFileStatus getStatus = audioFile.GetPropertyInfo(AudioFilePropertyId.MagicCookieData, out dataSize,
out isWritable);
if (getStatus != AudioFileStatus.Ok)
{
throw new IOException(string.Format(CultureInfo.CurrentCulture,
Resources.LosslessSampleDecoderGetCookieInfoError, getStatus));
}
if (dataSize == 0)
{
return(IntPtr.Zero);
}
IntPtr cookie = audioFile.GetProperty(AudioFilePropertyId.MagicCookieData, dataSize);
AudioConverterStatus setStatus = converter.SetProperty(AudioConverterPropertyId.DecompressionMagicCookie,
dataSize, cookie);
if (setStatus != AudioConverterStatus.Ok)
{
throw new IOException(string.Format(CultureInfo.CurrentCulture,
Resources.LosslessSampleDecoderSetCookieError, setStatus));
}
return(cookie);
}
internal NativeAudioConverter(ref AudioStreamBasicDescription inputDescription, ref AudioStreamBasicDescription outputDescription, NativeAudioFile audioFile)
{
Contract.Requires(audioFile != null);
Contract.Ensures(_handle != null);
Contract.Ensures(!_handle.IsClosed);
Contract.Ensures(_inputCallback != null);
Contract.Ensures(_audioFile != null);
Contract.Ensures(_audioFile == audioFile);
AudioConverterStatus status = SafeNativeMethods.AudioConverterNew(ref inputDescription,
ref outputDescription, out _handle);
if (status != AudioConverterStatus.Ok)
{
throw new IOException(string.Format(CultureInfo.CurrentCulture,
Resources.NativeAudioConverterInitializationError, status));
}
_inputCallback = InputCallback;
_audioFile = audioFile;
}