private void SeekHeader()
{
byte[] buffer = new byte[4];
do
{
// read 4 bytes (possible header)
int read = source.Read(buffer, 0, 4);
// less than 4 bytes read -> EOF
if(read < 4)
{
break;
}
// check for typical header strucure
if(SyncCheck(buffer))
{
// load the header bytes into the header class
Header head = new Header(buffer, (source.Position-4));
// extract header information and do another check for invalid values
if(head.Init())
{
// if frame contains CRC bytes, copy them to the header
if(head.crc)
{
source.Read(head.crcbytes, 0, 2);
source.Seek(-2, SeekOrigin.Current);
}
// check if the frame length matches the header data
byte[] syncbytes = new byte[4];
long currentpos = source.Position;
source.Seek(head.NextFrame(), SeekOrigin.Begin);
source.Read(syncbytes, 0, 4);
source.Seek(-1, SeekOrigin.Current);
// do we have another header?
if(SyncCheck(syncbytes))
{
// first header?
if(headerstream.Count <= 0)
{
if(SyncCompare(buffer, syncbytes)) // check if MPEG Version / Layer matches those of the next header (to reduce chance to catch noise)
{
comparebuffer = (byte[])buffer.Clone();
// we have found a frame!
headerstream.Add(head);
Console.WriteLine(head.ToString());
//break;
}
else
{
// resume search where we left
source.Seek(currentpos, SeekOrigin.Begin);
}
}
else // not the first header, so we don't do more checks to save some time
{
// we have found a frame!
headerstream.Add(head);
//Console.WriteLine(head.ToString());
}
}
}
}
// move 1 byte per cycle (instead of 4)
source.Seek(-3, SeekOrigin.Current);
} while (true);
Console.WriteLine("Frames: " + headerstream.Count.ToString());
if(headerstream.Count <= 0)
{
throw new Exception("Could not find MPEG headers");
}
}
public Frame(Header frameheader, Stream sourceStream)
{
scfsi[0] = new bool[4];
scfsi[1] = new bool[4];
part_23_length[0] = new int[2];
part_23_length[1] = new int[2];
big_values[0] = new int[2];
big_values[1] = new int[2];
global_gains[0] = new int[2];
global_gains[1] = new int[2];
sf_compress[0] = new int[2];
sf_compress[1] = new int[2];
header = frameheader;
source = sourceStream;
// let's get our frame's data
byte[] data = new byte[header.framelength];
long org_pos = source.Position;
int headlen = (header.crc) ? 6 : 4;
source.Seek(header.position+headlen, SeekOrigin.Begin);
source.Read(data, 0, header.framelength-headlen);
source.Seek(org_pos, SeekOrigin.Begin);
// split data
// select sidedata length
int sidedata_len = 0;
if(header.mpegversion == Header.MPEG_V1)
{
if(header.channelmode == Header.MONO)
{
sidedata_len = 17;
}
else
{
sidedata_len = 32;
}
}
else
{
if(header.channelmode == Header.MONO)
{
sidedata_len = 9;
}
else
{
sidedata_len = 17;
}
}
// init buffers
sidedata = new byte[sidedata_len];
byte[] mdata = new byte[data.Length - sidedata_len];
// write the data into the buffers
MemoryStream audiodata = new MemoryStream(data);
audiodata.Read(sidedata, 0, (int)sidedata.Length);
audiodata.Read(mdata, 0, (int)mdata.Length);
// create stream
maindata = new MemoryStream(mdata);
Parse_sidedata();
}
