/// <summary>
/// Parse the VDX to locate individual chunks
/// </summary>
private void parseVDX(GJD.RLData? rlData)
{
long stop;
// Final stream position
if (rlData.HasValue)
{
stop = rlData.Value.offset + rlData.Value.length;
}
else
{
stop = file.BaseStream.Length;
}
VDXHeader header = new VDXHeader();
VDXChunkHeader chunk = new VDXChunkHeader();
// Initialise queue's
audioOffsets = new Queue<long>();
videoOffsets = new Queue<long>();
// Read VDX header
header.ID = file.ReadUInt16();
if (header.ID != 0x9267)
throw new Exception("Invalid VDX header");
header.Unknown1 = file.ReadByte();
header.Unknown2 = file.ReadByte();
header.Unknown3 = file.ReadByte();
header.Unknown4 = file.ReadByte();
header.FPS = file.ReadUInt16();
//fps = (byte)header.FPS;
try
{
while (file.BaseStream.Position < stop)
{
// Read VDX chunk header
chunk = readChunkHeader();
// Add offsets where appropriate
switch (chunk.BlockType)
{
case VDXBlockType.Video:
videoFrames++;
goto case VDXBlockType.Zero;
case VDXBlockType.Zero:
videoMaster.Enqueue(file.BaseStream.Position - VDXChunkHeader.size);
break;
case VDXBlockType.Sound:
audioOffsets.Enqueue(file.BaseStream.Position - VDXChunkHeader.size);
break;
case VDXBlockType.Image:
imageOffset = file.BaseStream.Position - VDXChunkHeader.size;
break;
}
// Seek to next chunk
file.BaseStream.Seek(chunk.DataSize, System.IO.SeekOrigin.Current);
}
} catch {
audio = null;
videoFrames = 1;
}
}
/* The LZSS algorithm - http://wiki.xentax.com/index.php/LZSS
*
* Compression
* Set up parameters
* N Circular buffer size
* F Length window size
* Threshold Minimum compression size (minimum length for a match)
* BufPos Initial buffer position. Generally N - F
* BufVoid Initial fill byte.
*
* To compress
* Try to find longest sequence that is also in buffer
* If length >= Threshold, save offset and length in output file. record literal to buffer
* If no match, copy literal byte to output and repeat
*
* To record if compression or literal copy made, set special flag byte,
*
*
* Decompression
* Done in reverse order. Parameters need to be known.
* Pseudo:
*
* while InputPos < InputSize do
* begin
*
* FlagByte := Input[InputPos++]
* for i := 1 to 8 do
* begin
*
* if (FlagByte and 1) = 0 then
* begin
*
* OfsLen := Input[InputPos] + Input[InputPos + 1] shl 8
* InputPos += 2
* if OfsLen = 0 then
* Exit;
*
* Length := OfsLen and LengthMask + Threshold
* Offset := (BufPos - (OfsLen shr LengthBits)) and (N - 1)
* copy Length bytes from Buffer[Offset] onwards
* while increasing BufPos
*
* end
* else
* begin
*
* copy 1 byte from Input[InputPos]
* InputPos += 1
*
* end
* FlagByte := FlagByte shr 1
*
* end
* end
*
* Length bits descibes number of bits to find F. Above assumes length of buffer reference
* in lower bit of the word. lenght mask = (1 << lenbits) - 1
*
* also assumed buffer offset relative to current write position. if absolute, BufPos subtraction unneeded
*
* Buffer is circular. wrap offset.
*
* mirror output writes to history buffer
*
* in most cases, data from history buffer will be byte-wise.
*/
private void decompress(System.IO.BinaryReader inStream, ref VDXChunkHeader header, out System.IO.MemoryStream stream)
{
stream = new System.IO.MemoryStream();
uint i, j, N, F, initwrite;
byte flagbyte, tempa;
uint offsetlen, length, offset, bufpos;
byte[] hisbuff;
N = (uint)(1 << (16 - header.LengthBits)); // History buffer size
hisbuff = new byte[N]; // History buffer
F = (uint)(1 << header.LengthBits); // Window size
initwrite = N - F; // Initial history write pos
bufpos = 0;
for (i = 0; i < N; i++)
hisbuff[i] = 0; // Init history buffer
long final = header.DataSize + inStream.BaseStream.Position;
while (inStream.BaseStream.Position < final)
{
flagbyte = inStream.ReadByte();
for (i = 1; i <= 8; i++)
{
if (inStream.BaseStream.Position < final)
{
if ((flagbyte & 1) == 0)
{
offsetlen = inStream.ReadUInt16();
if (offsetlen == 0)
break;
length = (offsetlen & header.LengthMask) + 3;
offset = (bufpos - (offsetlen >> header.LengthBits)) & (N - 1);
for (j = 0; j < length; j++)
{
tempa = hisbuff[(offset + j) & (N - 1)];
stream.WriteByte(tempa);
hisbuff[bufpos] = tempa;
bufpos = (bufpos + 1) & (N - 1);
}
}
else
{
tempa = inStream.ReadByte();
stream.WriteByte(tempa);
hisbuff[bufpos] = tempa;
bufpos = (bufpos + 1) & (N - 1);
}
flagbyte = (byte)(flagbyte >> 1);
}
}
}
}
/// <summary>
/// Read in the header for the current chunk
/// </summary>
/// <returns>Chunk header structure</returns>
private VDXChunkHeader readChunkHeader()
{
VDXChunkHeader chunk = new VDXChunkHeader();
chunk.BlockType = (VDXBlockType)file.ReadByte();
chunk.PlayCmd = (VDXChunkPlayCmd)file.ReadByte();
chunk.DataSize = file.ReadInt32();
chunk.LengthMask = file.ReadByte();
chunk.LengthBits = file.ReadByte();
return chunk;
}
