private void Initialize(Header header)
{
// REVIEW: allow customizable scale factor
float scalefactor = 32700.0f;
int mode = header.mode();
int layer = header.layer();
int channels = mode == Header.SINGLE_CHANNEL ? 1 : 2;
// set up output buffer if not set up by client.
if (m_Output == null)
m_Output = new SampleBuffer(header.frequency(), channels);
float[] factors = m_Equalizer.BandFactors;
//Console.WriteLine("NOT CREATING SYNTHESIS FILTERS");
m_LeftChannelFilter = new SynthesisFilter(0, scalefactor, factors);
// REVIEW: allow mono output for stereo
if (channels == 2)
m_RightChannelFilter = new SynthesisFilter(1, scalefactor, factors);
m_OutputChannels = channels;
m_OutputFrequency = header.frequency();
m_IsInitialized = true;
}
/// <summary>
/// Decodes one frame from an MPEG audio bitstream.
/// </summary>
/// <param name="header">
/// Header describing the frame to decode.
/// </param>
/// <param name="stream">
/// Bistream that provides the bits for the body of the frame.
/// </param>
/// <returns>
/// A SampleBuffer containing the decoded samples.
/// </returns>
public virtual ABuffer DecodeFrame(Header header, Bitstream stream)
{
if (!m_IsInitialized)
{
Initialize(header);
}
int layer = header.layer();
m_Output.ClearBuffer();
IFrameDecoder decoder = RetrieveDecoder(header, stream, layer);
decoder.DecodeFrame();
m_Output.WriteBuffer(1);
return m_Output;
}
protected internal virtual IFrameDecoder RetrieveDecoder(Header header, Bitstream stream, int layer)
{
IFrameDecoder decoder = null;
// REVIEW: allow channel output selection type
// (LEFT, RIGHT, BOTH, DOWNMIX)
switch (layer)
{
case 3:
if (m_L3Decoder == null)
{
m_L3Decoder = new LayerIIIDecoder(stream, header, m_LeftChannelFilter, m_RightChannelFilter, m_Output,
(int) OutputChannelsEnum.BOTH_CHANNELS);
}
decoder = m_L3Decoder;
break;
case 2:
if (m_L2Decoder == null)
{
m_L2Decoder = new LayerIIDecoder();
m_L2Decoder.Create(stream, header, m_LeftChannelFilter, m_RightChannelFilter, m_Output,
(int) OutputChannelsEnum.BOTH_CHANNELS);
}
decoder = m_L2Decoder;
break;
case 1:
if (m_L1Decoder == null)
{
m_L1Decoder = new LayerIDecoder();
m_L1Decoder.Create(stream, header, m_LeftChannelFilter, m_RightChannelFilter, m_Output,
(int) OutputChannelsEnum.BOTH_CHANNELS);
}
decoder = m_L1Decoder;
break;
}
if (decoder == null)
{
throw NewDecoderException(DecoderErrors.UNSUPPORTED_LAYER, null);
}
return decoder;
}
private void InitBlock()
{
m_CRC = new Crc16[1];
m_SyncBuffer = new sbyte[4];
m_FrameBytes = new sbyte[BUFFER_INT_SIZE*4];
m_FrameBuffer = new int[BUFFER_INT_SIZE];
m_Header = new Header();
}