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DreamWorks BLB Resource, Music and Sound Formats

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Автор материала: Valery V. Anisimovsky ([email protected])

In this document I'll try to describe the format of DreamWorks BLB resource files as well as the format of sound/music files stored in BLB archives. These formats are used in the game The Neverhood (perhaps, in some other DreamWorks games).

The files this document deals with have extensions: .BLB.

Throughout this document I use C-like notation.

All numbers in all structures described in this document are stored in files using little-endian (Intel) byte order.

1. BLB Resource Files

All game files of The Neverhood are stored in BLB resource files.
Each BLB file has the following header:

struct BLBHeader 
char szID[4]; 
BYTE bUnknown; 
WORD wDataSize; 
DWORD dwFileSize; 
DWORD dwNumber; 

szID -- string ID is always "x40x49x00x02".

bID -- byte ID is always 0x07.

wDataSize -- the size of data section of BLB file (see below).

dwFileSize -- the size of BLB file.

dwNumber -- the number of files stored in BLB file.

After the header comes the array of (dwNumber) file IDs. Each file ID is a DWORD identifying a file in BLB archive.

After the file IDs array comes the array of (dwNumber) directory entries. Each directory entry contains the info on a file in BLB archive. Each such entry has the following format:

struct BLBDirEntry 
BYTE bType; 
BYTE bAction; 
WORD wDataIndex; 
DWORD dwUnknown; 
DWORD dwStart; 
DWORD dwFileID; 
DWORD dwOutSize; 

bType -- the type of the file:
0x07 -- sound effect,
0x08 -- music,
0x0A -- video file (SMK -- Smacker video, www.smacker.com), there're some more types, but their purpose is not so evident (e.g. 0x02 seems to be graphic file type).

bAction -- defines the action which should be performed for the file:
0x01 -- none: the file is non-compressed, no additional actions are required,
0x03 -- decompress: the file is PKWARE-compressed (see below),
0x65 -- fake: the file is fake, that is no file is really present (see below).

wDataIndex -- the index into file data array (see below) for the byte correspondent to the file.

dwStart -- the starting position of the file relative to the beginning of the BLB archive.

dwFileID -- this field is only relevant for fake files: fake files directory entries are just placeholders, there's no real file in the archive for the fake file directory entry, but such entry points to some other file (perhaps, in other BLB archive) with the file ID equal to (dwFileID) which should be used instead of the correspondent fake file. So, fake file is a kind of alias for other (non-fake) file. Note, that, in principle, fake file may be an alias for another fake file, etc., but finally there should be non-fake file in the chain of such redirections.

dwOutSize -- the output size of the file: for non-compressed files that's just the size of the file, for PKWARE-compressed files that's the size of decompressed file, for fake files use the value from the directory entry of the correspondent non-fake file.

After the array of directory entries comes the data section. This is the array of (wDataSize) bytes. Let's call these bytes "shifts". The shift value for the file may be obtained by getting the byte with index (wDataIndex) (see above) from the file data array (indices are zero-based). If the index value is too large (not less than data section size (wDataSize)), the shift value should be set to default (0xFF).

After the file data section come files contained in BLB archive.

2. Decompression of PKWARE-compressed Files

I will not describe here the algorithm of PKWARE decompression. What I'll explain is the easy way you may use to access PKWARE-compressed files via PKWARE's library PKWARE.DLL. This library is supplied with GAP's BLB RF plug-in (see below).

Here's the sample C code (using Win32 API):

// decompression function -- returns zero on success 

DWORD (__cdecl *Uncompress) 
char *outputBuffer, 
DWORD *pOutSize, 
char *inputBuffer, 
DWORD dwSize 

// first, load the library 

HINSTANCE hDllInst=LoadLibrary("pkware.dll"); 

// get the decompression function address 

Uncompress=(DWORD (__cdecl *)(char*, DWORD*, char*, DWORD))GetProcAddress(hDllInst,"Uncompress"); 

// decompress file -- it's assumed here that input buffer contains compressed 

// file loaded from BLB archive and output buffer is allocated and has proper 

// size (that is, (dwOutSize) value from the corresponding directory entry) 


// now (outputBuffer) contains decompressed file and (dwOutSize) is set to 

// decompressed file size (you should use directory entry value of output 

// size for output buffer allocation)

3. BLBSFX Sound and Music Files

As was pointed out above, files with type bytes 0x07 and 0x08 are sound and music files. All of them are of the same format which I refer to as BLBSFX. BLBSFX file has no header, it's just compressed (or non-compressed) waveform stream. All sound/music files in The Neverhood are 16-bit mono 22050 Hz. If the shift value for the BLBSFX file is 0xFF, the file in not compressed and in this case, it's just PCM waveform stream (signed 16-bit).


Otherwise, if the shift byte differs from 0xFF, BLBSFX file is compressed using DW ADPCM compression algorithm. Refer to the following section for the description of DW ADPCM decompression scheme. Note that most of sound files in The Neverhood are PKWARE-compressed, that is you should first decompress them (e.g. using PKWARE.DLL and the approach described above) and then apply DW ADPCM decompression scheme (if needed). All music files are not PKWARE-compressed, but most of them are DW ADPCM compressed.

4. DW ADPCM Decompression Algorithm

During the decompression SHORT variable should be maintained. Decompression uses shift value, so it should be obtained first.

Here's the code which decompresses DW ADPCM compressed BLBSFX file:

BYTE bShift; // shift value 

char *inputBuffer[dwSize]; 

SHORT iCurValue; 


for (i=0;i<dwSize;i++) 
iCurValue+=(signed short)inputBuffer[i]; 

Output() is just a placeholder for any action you would like to perform for decompressed sample value.

5. Credits

Dmitry Kirnocenskij ([email protected])
Provided me with info on dealing with PKWARE-compressed files.

Valery V. Anisimovsky ([email protected])
On these sites you can find my GAP program which can deal with BLB resource files, play back BLBSFXes from them and convert BLBSFXes to WAVs. There's also complete source code of GAP and all its plug-ins there, including BLB and BLBSFX plug-ins, which could be used for further details on how you can deal with these formats.


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