static OptionalHeader ReadXingHeader([NotNull] FrameReader reader, [NotNull] FrameHeader header)
{
// Xing header (if present) is located after the side info
reader.BaseStream.Position = reader.FrameStart + 4 + header.SideInfoLength;
var result = new OptionalHeader();
var headerId = reader.ReadHeaderId();
if (!headerId.Equals("Xing", StringComparison.Ordinal) &&
!headerId.Equals("Info", StringComparison.Ordinal))
{
return(result);
}
// Both fields are optional, even if the header is present
var flags = reader.ReadUInt32BigEndian();
if ((flags & 1) == 1)
{
result.FrameCount = reader.ReadUInt32BigEndian();
}
if ((flags >> 1 & 1) == 1)
{
result.ByteCount = reader.ReadUInt32BigEndian();
}
return(result);
}
static int DetermineBitRate([NotNull] FrameHeader frameHeader, OptionalHeader optionalHeader)
{
// If the BitRate can't be calculated because of an incomplete or missing VBR header, assume CBR
if (optionalHeader.Incomplete)
{
return(frameHeader.BitRate * 1000);
}
return((int)Math.Round(
optionalHeader.ByteCount * 8 /
(optionalHeader.FrameCount * frameHeader.SamplesPerFrame / (double)frameHeader.SampleRate)));
}
static OptionalHeader ReadVbriHeader([NotNull] FrameReader reader)
{
// VBRI header (if present) is located 32 bytes past the frame header
reader.BaseStream.Position = reader.FrameStart + 36;
var result = new OptionalHeader();
if (!reader.ReadHeaderId().Equals("VBRI", StringComparison.Ordinal))
{
return(result);
}
reader.BaseStream.Seek(6, SeekOrigin.Current);
result.ByteCount = reader.ReadUInt32BigEndian();
result.FrameCount = reader.ReadUInt32BigEndian();
return(result);
}
