/// <summary>
/// Returns a VBRData structure from an index in a byte array
/// </summary>
/// <param name="index">Index</param>
/// <param name="data">Byte array</param>
/// <returns>VBRData structure</returns>
private static VBRData FindVBR(int index, Byte[] data)
{
VBRData result;
String id = String.Format("{0}{1}{2}{3}", (Char)data[index], (Char)data[index + 1], (Char)data[index + 2], (Char)data[index + 3]);
// Check for VBR header at given position
if (id == VBRHeaderID.Xing)
{
result = GetXingInfo(index, data);
}
else if (id == VBRHeaderID.FhG)
{
result = GetFhGInfo(index, data);
}
else
{
result = new VBRData();
}
return(result);
}
/// <summary>
/// Returns VBRData structure from an FhG info tag
/// </summary>
/// <param name="index">Index in array</param>
/// <param name="data">Data byte array</param>
/// <returns>VBRData structure</returns>
private static VBRData GetFhGInfo(int index, Byte[] data)
{
VBRData result = new VBRData();
// Extract FhG VBR info at given position
result.Found = true;
result.ID = Encoding.ASCII.GetBytes(VBRHeaderID.FhG);
result.Scale = data[index + 9];
result.Bytes =
data[index + 10] * 0x1000000 +
data[index + 11] * 0x10000 +
data[index + 12] * 0x100 +
data[index + 13];
result.Frames =
data[index + 14] * 0x1000000 +
data[index + 15] * 0x10000 +
data[index + 16] * 0x100 +
data[index + 17];
return(result);
}
/// <summary>
/// Find a valid MP3 frame in a byte array. Sets "m_Frame.Found = true"
/// </summary>
/// <param name="data">Byte array of data from MP3 file</param>
/// <param name="vbrHeader">Method sets this variable to a VBRData struct, if frame found</param>
private void FindFrame(Byte[] data, ref VBRData vbrHeader)
{
Byte[] headerData = new Byte[4];
// Search for valid frame
Buffer.BlockCopy(data, 0, headerData, 0, 4);
int size = data.Length - 4;
for (int i = 0; i < size; i++)
{
// Decode data if frame header found
if (IsFrameHeader(headerData))
{
DecodeHeader(headerData);
int nextHeader = i + GetFrameLength(m_Frame);
if (nextHeader < size)
{
// Check for next frame and try to find VBR header
if (ValidFrameAt(nextHeader, data))
{
m_Frame.Found = true;
m_Frame.Position = i;
m_Frame.Size = GetFrameLength(m_Frame);
m_Frame.Xing = IsXing(i + headerData.Length, data);
vbrHeader = FindVBR(i + GetVBRFrameOffset(m_Frame), data);
break;
}
}
}
// Prepare next data block
headerData[0] = headerData[1];
headerData[1] = headerData[2];
headerData[2] = headerData[3];
headerData[3] = data[4 + i];
}
}
