/// <summary>
/// Parses the audio output mode of this frame's audio data.
/// </summary>
/// <param name="frameHeader">The 4 byte header for this frame.</param>
/// <returns>The audio output mode of this frame's audio data.</returns>
private static Channel ParseChannel(byte[] frameHeader)
{
Channel channel;
int channelValue = BitTools.MaskBits(frameHeader, 24, 2);
switch (channelValue)
{
case 3:
channel = Channel.SingleChannel;
break;
case 2:
channel = Channel.DualChannel;
break;
case 1:
channel = Channel.JointStereo;
break;
case 0:
channel = Channel.Stereo;
break;
default:
channel = Channel.SingleChannel; // ERROR CASE
break;
}
return(channel);
}
/// <summary>
/// Parses the version of the MPEG standard this frame header conforms to from the frame header.
/// </summary>
/// <param name="frameHeader"> The 4 byte header for this frame. </param>
/// <returns>
/// The version of the MPEG standard this frame conforms to.
/// 1 = Mpeg 1
/// 2 = Mpeg 2
/// 3 = Mpeg 2.5
/// </returns>
private static int ParseVersion(byte[] frameHeader)
{
int version;
int versionValue = BitTools.MaskBits(frameHeader, 11, 2);
switch (versionValue)
{
case 3:
version = 1;
break;
case 2:
version = 2;
break;
case 0:
version = 3;
break;
default:
version = -1; // ERROR
break;
}
return(version);
}
/// <summary>
/// Parses which complexity layer of the MPEG standard this frame conforms to from the frame header.
/// </summary>
/// <param name="frameHeader">The 4 byte header for this frame.</param>
/// <returns>The complexity layer this frame conforms to.</returns>
private static int ParseLayer(byte[] frameHeader)
{
int layer;
int layerValue = BitTools.MaskBits(frameHeader, 13, 2);
switch (layerValue)
{
case 3:
layer = 1;
break;
case 2:
layer = 2;
break;
case 1:
layer = 3;
break;
default:
layer = -1;
break;
}
return(layer);
}
/// <summary>
/// Initializes a new instance of the MpegFrame class.
/// </summary>
/// <param name="stream">
/// A stream with its position at the SyncPoint of the header.
/// </param>
public MpegFrame(Stream stream)
{
long startPostion = stream.Position;
byte[] frameHeader = new byte[FrameHeaderSize];
// Guard against a read error
if (stream.Read(frameHeader, 0, FrameHeaderSize) != FrameHeaderSize)
{
goto cleanup;
}
// Sync
int value = BitTools.MaskBits(frameHeader, 0, 11);
if (!(value == SyncValue))
{
goto cleanup;
}
this.Version = ParseVersion(frameHeader);
this.Layer = ParseLayer(frameHeader);
this.IsProtected = BitTools.MaskBits(frameHeader, 15, 1) == 1 ? false : true;
this.BitrateIndex = BitTools.MaskBits(frameHeader, 16, 4);
this.SamplingRateIndex = BitTools.MaskBits(frameHeader, 20, 2);
this.Padding = BitTools.MaskBits(frameHeader, 22, 1);
//// Private Bit = BitTools.MaskBits(_mp3FrameHeader,8,1); //USELESS
this.Channels = ParseChannel(frameHeader);
//// Joint Mode = ParseJoitMode(_mp3FrameHeader); //Not used by Mp3MSS
//// CopyRight = BitTools.MaskBits(_mp3FrameHeader,3,1); //Not used by Mp3MSS
//// Original = BitTools.MaskBits(_mp3FrameHeader,2,1); //Not used by Mp3MSS
//// Emphasis = ParseEmphasis(_mp3FrameHeader); //Not used by Mp3MSS
return;
cleanup:
stream.Position = startPostion;
frameHeader = null;
return;
}
