From 1803f3a710790afa1caeea4296e0328656270059 Mon Sep 17 00:00:00 2001
From: Aleteoryx <alyx@aleteoryx.me>
Date: Tue, 16 Jun 2026 13:47:14 -0400
Subject: [PATCH] kewl

---
 README.md                | 83 ++++++++++++++++++++++++++++++++++++++++
 pvrt.tcl                 |  9 +++--
 extract.tcl => unpac.tcl | 12 ++++--
 3 files changed, 97 insertions(+), 7 deletions(-)
 create mode 100644 README.md
 rename extract.tcl => unpac.tcl (86%)

diff --git a/README.md b/README.md
new file mode 100644
index 0000000000000000000000000000000000000000..55ec6ea555f153d6c563fb12fe0c1b35b3037a1f
--- /dev/null
+++ b/README.md
@@ -0,0 +1,83 @@
+script to extract the .PAC asset bundle format, present in (at least)
+magic the gathering for dreamcast. it also converts the PVRT textures
+to PNGs
+
+# usage:
+
+install tcl and imagemagick. in particular, make sure `convert` is
+present in $PATH. if you're on a unix, installing tcl should be
+trivial. on windows, it is available in a package called "magicsplat".
+YMMV.
+
+to run it, open a terminal and enter
+
+```
+$ ./unpac.tcl ./path/to/bundle.pac ./path/to/output/
+```
+
+this may take a while for a PAC with large images, as the PVRT->PNG
+decoder is largely implemented in tcl. optimization patches welcome.
+
+this will output a directory structure like:
+
+```
+./path/to/output/
+    xxxx.pvr - decompressed powervr texture image
+    xxxx.png - for each .pvr, a matching .png is created.
+
+    xxxx.njcm - ninja chunk model, raw 3d model data
+
+    xxxx.njtl - ninja texlist, texture mapping info for a model
+
+    xxxx.nmdm - ninja motion, animation
+
+    xxxx.bin - unknown decompressed record type
+    xxxx.rec - unknown record type
+```
+
+the PVRT converter is incomplete, and only supports the pixel/data
+modes present in magic the gathering. an unsupported PVRT will not be
+converted, but you can apply an external tool to it if need be.
+
+# details:
+
+.PAC is a pretty simple bundle format. it consists of a header, and a
+set of concatenated records, where each record begins with a 4-byte
+prefix specifying its type. it is a little-endian format.
+
+```
+Header Format (all values are 4 bytes):
+
+         +----------------+
+ 0x00    | "PAC\0" magic  |
+         +----------------+
+ 0x04    |  # of records  |
+         +----------------+
+ 0x08    | data start pos |
+         +----------------+
+ 0x0c    |  record 1 end  |
+ 0x10    |  record 2 end  |
+         |      ...       |
+ 0x??    |  record # end  |
+         +----------------+
+```
+
+the first record is data start bytes into the file, from the absolute
+beginning. it ends at record 1 end, and record 2 starts immediately
+after. the last entry in the record end table is the length of the
+file.
+
+4 record types are known:
+
+- `NZIP`, rest of record is deflate compressed data
+- `NJCM`, ninja chunk model
+- `NJTL`, ninja texlist
+- `NMDM`, ninja motion
+
+NZIP appears to be for storing PVRT images. the other types are
+well-known dreamcast sdk formats
+
+# license:
+
+if you pinky swear not to sue me for anything I pinky swear not to sue
+you for anything. not like I have lawyer money, anyway
diff --git a/pvrt.tcl b/pvrt.tcl
index 46681a6c4048cb172f88b57949d15c4e76fbd23d..95ab6c74d86b64cd12ffa438f6c934851583a4cc 100644
--- a/pvrt.tcl
+++ b/pvrt.tcl
@@ -204,9 +204,8 @@ proc ::pvrt2tga::convert {src dst} {
 		seek $sfp 16
 	}
 	if {[read $sfp 4] != "PVRT"} {
-		puts "$src not PVRT"
 		close $sfp
-		return
+		return -code error "missing PVRT magic"
 	}
 
 	binary scan [read $sfp 12] iccsss len pfmt dfmt _ w h
@@ -216,7 +215,11 @@ proc ::pvrt2tga::convert {src dst} {
 	set pdec [pfmt::lookup $pfmt]
 	set ddec [dfmt::lookup $dfmt]
 
-#	puts "$src $dst $pdec $ddec $w $h"
+	if {$pdec == ""} {
+		return -code error "unsupported pixel format: $pfmt"
+	} elseif {$ddec == ""} {
+		return -code error "unsupported data format: $dfmt"
+	}
 
 	$ddec $pdec srcbuf dstbuf $w $h
 
diff --git a/extract.tcl b/unpac.tcl
similarity index 86%
rename from extract.tcl
rename to unpac.tcl
index 99335cf9c15a5506be8d214c27ffa10cad361179..5f9e36add326de54f75ae9d0f928da372d74322e 100755
--- a/extract.tcl
+++ b/unpac.tcl
@@ -67,10 +67,14 @@ foreach endpt $endtab {
 		close $fp2
 
 		if {$ext == "pvr"} {
-			pvrt2tga::convert ${filebase}.${ext} ${filebase}.tga
-			exec -- convert ${filebase}.tga ${filebase}.png
-			file delete ${filebase}.tga
-			puts "${file}: record $id (decompressed): Converted to PNG"
+			if {[catch {
+				pvrt2tga::convert ${filebase}.${ext} ${filebase}.tga
+				exec -- convert ${filebase}.tga ${filebase}.png
+				file delete ${filebase}.tga
+				puts "${file}: record $id (decompressed): Converted to PNG"
+			} why]} {
+				puts "${file}: record $id (decompressed): PNG Conversion Failed: $why"
+			}
 		}
 	}
 	NJCM {