Left 4 Dead — Archive & Texture Formats

Source: XeNTaX forum knowledge extraction (2008–2017). Covers Left 4 Dead PC (Source engine) and Xbox 360 (L4D360). Also applies to Portal: Still Alive (Xbox 360).

1. VPK Archives (PC — Source Engine)

With the L4D demo release, Valve shipped game files not in the standard .gcf format used by other Source games, but in .vpk files. These VPKs differ from the earlier .vpk used in Vampire: The Masquerade — Bloodlines.

Tools

Tool	Purpose	Notes
`Gibbed.Valve.ExtractPackage`	VPK extraction	Rick (Gibbed); requires .NET Framework 2.0; fails silently on XP unless .NET 2.0 installed

2. Xbox 360: VTFX Textures

Xbox 360 version uses a slightly modified Valve VTF format called VTFX. Files are big-endian — byte-swap before viewing.

VTFX File Header

struct VTFXFileHeader {
 int fileSignature; // 0x56544658 ("VTFX")
 int version1; // 0x00000360
 int version2; // 0x00000008
 int headerSize; // 0x00000044
 int unknown;
 short width;
 short height;
 short unknown; (x4)
 float reflectivityX;
 float reflectivityY;
 float reflectivityZ;
 float bumpMapScale;
 int imageFormat;
 int unknown; (x3)
 int headerSize2; // 0x00000044
};

Key Header Offsets

Offset	Type	Field
`0x0C`	long (BE)	`LZMA_OFF` — offset where LZMA data begins
`0x14`	short (BE)	width
`0x16`	short (BE)	height

Embedded Image Structure

Image data is LZMA-compressed (cfarl, 2017)
Decompressed payload = .textures file containing DXT5 big-endian image
Mipmap order is inverted: smallest mip first, largest (main) mip last
DXT5 data size = width × height. Extract main mip by counting back width × height bytes from end of decompressed file.

LZMA Payload Header (at `LZMA_OFF`, little-endian)

Offset	Type	Field
+0x00	dstring(4)	`LZMA` id
+0x04	long	`SIZE` (uncompressed size)
+0x08	long	`ZSIZE` (compressed size)
+0x0C	dstring(5)	`LZMA_PROP` (5-byte LZMA properties)

QuickBMS Extraction Script (cfarl / Acewell, 2017)

# script for QuickBMS http://aluigi.altervista.org/quickbms.htm
endian big
idstring "VTFX"

# Step 1. Extract lzma data from the vtfx file
goto 0xc
get LZMA_OFF long

goto 0x14
get IMG_WIDTH short
get IMG_HEIGHT short

goto LZMA_OFF
endian little
getdstring LZMA 4
get SIZE long
get ZSIZE long
getdstring LZMA_PROP 5

get NAME basename
string NAME + ".textures"
comtype lzma_dynamic LZMA_PROP
savepos OFFSET
clog NAME OFFSET ZSIZE SIZE

# Step 2. Extract dds data from end of .textures file
Open . NAME 1
get SIZE_TEXTURES_FILE asize 1
XMath IMG_SIZE "(IMG_WIDTH * IMG_HEIGHT)"
XMath OFFSET_IMG "(SIZE_TEXTURES_FILE - IMG_SIZE)"
get NAME basename
string NAME + ".texture"
log NAME OFFSET_IMG IMG_SIZE 1

# Step 3. Byte-swap (big-endian -> little-endian) the .texture data
Open . NAME 2
xmath NUM_SHORTS "IMG_SIZE / 2"
for i = 0 < NUM_SHORTS
 encryption swap 2
next i
get NAME basename
string NAME + "_swp.texture"
log NAME 0x0 IMG_SIZE 2

# Step 4. Prepend a DXT5 DDS header
Open . NAME 3
encryption "" ""
set MEMORY_FILE binary "\x44\x44\x53\x20\x7c\x00..." # DDS "DDS " header
putVarChr MEMORY_FILE 0xc IMG_HEIGHT short
putVarChr MEMORY_FILE 0x10 IMG_WIDTH short
string NAME += ".dds"
get SIZE asize MEMORY_FILE
append
log NAME 0 SIZE MEMORY_FILE
log NAME 0 IMG_SIZE 3

Practical Workflow (cfarl / Acewell, 2017)

Use BMS script to extract LZMA data → .textures file
Take last width × height bytes (largest mip) as image data
Byte-swap back to little-endian
Prepend DXT5 DDS header
To re-import: Recompress with own LZMA (QuickBMS reimport unreliable — compressed size differs)
Maintain same image format, size, mipmaps; byte-swap back to big-endian after editing
Fix for "english shadow" (stale mipmaps): Zero out all bytes before DDS image so leftover mip data doesn't display

3. Xbox 360: 360.zip Archives

Xbox 360 version stores all files in 360.zip files. These cannot be extracted by normal zip tools despite looking identical to standard zip.

Extraction

Tool: XZIP.rar extractor (TheGeneral) — works on L4D and Portal: Still Alive 360.zip files

Rebuilding

Rezip files into an uncompressed zip archive — game still loads everything
Gotcha: Must produce uncompressed archive; compression breaks injection

4. Script/Data Encryption (Source SDK)

For Steam versions, the Source SDK includes a tool to encrypt/decrypt .dat/.txt files.

Tools Reference

Tool	Purpose	Author
Gibbed.Valve.ExtractPackage	VPK extraction (PC)	Rick (Gibbed)
XZIP	360.zip extraction (Xbox 360)	TheGeneral
QuickBMS + VTFX script	VTFX LZMA → DDS extraction	cfarl / Acewell
Source SDK	.dat/.txt encrypt/decrypt	Valve

Key Facts Summary

PC L4D uses .vpk archives (not .gcf)
Xbox 360 L4D uses 360.zip archives and VTFX textures
VTFX = modified Valve VTF with LZMA-compressed payload, big-endian DXT5, inverted mip order (smallest first, largest last)
VTFX header magic: 0x56544658 ("VTFX"); image dims at 0x14/0x16; LZMA offset pointer at 0x0C
VTFX also applies to Portal: Still Alive on Xbox 360

1. VPK Archives (PC — Source Engine)​

Tools​

2. Xbox 360: VTFX Textures​

VTFX File Header​

Key Header Offsets​

Embedded Image Structure​

LZMA Payload Header (at LZMA_OFF, little-endian)​

QuickBMS Extraction Script (cfarl / Acewell, 2017)​

Practical Workflow (cfarl / Acewell, 2017)​

3. Xbox 360: 360.zip Archives​

Extraction​

Rebuilding​

4. Script/Data Encryption (Source SDK)​

Tools Reference​

Key Facts Summary​