zoom-zt2
zoom-zt2 copied to clipboard
mungewell
ZD2: bytes 0x8-0xF
Anyone has any ideas about the data represented by the bytes 0x8-0xF in the ZD2 files? These are the 8 (mostly non-zero) bytes following the file magic string.
These bytes appear to be different across different effects, though It's not very obvious what is encoded there. In fact these bytes are among the few which are different between different versions of a given ZD2. For example:
| filename | version | bytes [0x8-0xF] |
|---|---|---|
| AIR.ZD2 | v1.50 | [19 EB FF B4 07 00 00 00] |
| AIR.ZD2 | v1.40 | [89 4B 53 4B 03 00 00 00] |
| AIR.ZD2 | v1.30 | [D3 19 D6 C4 03 00 00 00] |
I'd love to believe that it's just some random non-initialized memory but given it's position and peculiarity between versions there is likely some specific meaning to these. Some ideas I considered so far without success:
- checksum (md5, crc32); in general it's not clear what could be checksum'ed here, since the contained BMP icon, the ELF payload, and descriptions appear to remain the same between the versions in this case.
- some bit-field, perhaps describing pedal models this ZD2 is supported on. Updates are often to add models but it's not obvious how those are encoded.
- a bunch of some integer values (it does not appear to be floating-point bytes); well, that's not very meaningful
Love that you are asking these questions, I suspect that every Byte of the ZD2 has meaning...
'Air' is used pretty on every pedal.
$ find -name "list_sorted.txt" -exec grep 0x398a8d8aea4072acb0174117630e0f91 {} \;
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./A1 FOUR/unzipped/AIR.ZD2
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./A1X FOUR/unzipped/AIR.ZD2
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./G1X FOUR/unzipped/AIR.ZD2
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./G11/unzipped/AIR.ZD2
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./B1X FOUR/unzipped/AIR.ZD2
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./G1 FOUR/unzipped/AIR.ZD2
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./B1 FOUR/unzipped/AIR.ZD2
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./G3n/unzipped/AIR.ZD2
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./B3n/unzipped/AIR.ZD2
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./G6/unzipped/AIR.ZD2
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./G5n/unzipped/AIR.ZD2
0x09000010 : Air (v1.50, 6.40%), 0x398a8d8aea4072acb0174117630e0f91, ./G3Xn/unzipped/AIR.ZD2
So the Bytes that you are questioning are in the first line...
$ hexdump -C "./G1X FOUR/unzipped/AIR.ZD2" | head
00000000 5a 44 4c 46 78 00 00 00 19 eb ff b4 07 00 00 00 |ZDLFx...........|
00000010 01 00 01 00 01 00 00 00 80 00 00 00 00 00 00 00 |................|
00000020 00 00 00 00 00 00 00 00 80 00 00 00 00 00 00 00 |................|
And is the first 4 bytes of the 'Unknown' section.
$ python3 ../decode_effect.py -d "./G1X FOUR/unzipped/AIR.ZD2"
Container:
length = 120
hexdump = hexundump("""
0000 19 EB FF B4 07 00 00 00 01 00 01 00 01 00 00 00 ................
0010 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0020 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0030 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0050 01 .
""")
unknown = b'\x19\xeb\xff\xb4\x07\x00\x00\x00\x01\x00\x01\x00\x01\x00\x00\x00'... (truncated, total 81)
version = u'1.50' (total 4)
group = 9
id = 150994960
aname = u'Air' (total 3)
bname = b"Air\x00\x00\x00\x00\x00\xae'=" (total 11)
name = u'Air' (total 3)
groupname = u'REVERB' (total 6)
hex3 = hexundump("""
0000 00 5A 27 09 1B 98 .Z'...
""")
unknown3 = b"\x00Z'\t\x1b\x98" (total 6)
unknown4 = Container:
unknown4 = ListContainer:
0
1
0
1
0
0
0
0
ICON = Container:
length = 182
data = b'BM\xb6\x00\x00\x00\x00\x00\x00\x00>\x00\x00\x00(\x00'... (truncated, total 182)
TXJ1 = Container:
length = 56
data = b'\x95\x94\x89\xae\x96\xc2\x82\xe8\x82\xcc\x8b\xf3\x8bC\x8a\xb4'... (truncated, total 56)
TXE1 = Container:
length = 75
description = u'This effect reproduces the ambie'... (truncated, total 75)
INFO = Container:
length = 20
data = b'\x00\x00\x00\x00REVREVERB\x00\x00\x00' (total 16)
dspload = 16.0
DATA = Container:
length = 13169
data = b'\x7fELF\x01\x01\x01@\x00\x00\x00\x00\x00\x00\x00\x00'... (truncated, total 13169)
PRMJ = Container:
length = 796
data = b'{ \r\n\t"Parameter'... (truncated, total 796)
PRME = Container:
length = 715
xml = u'{ \r\n\t"Parameters":[ \r\n\t\t{ \r\n\t'... (truncated, total 715)
The reason I mention all of this, is that it becomes trivial to decode ALL of the effects and then compare the various bits of them.
There is no duplication in the effects of the G1 Four, and eye-balling it the values are evenly spread so this could very likely be some for of checksum (if so it's probably CRC32 in the same way that the midi link uses).
$ find G1\ FOUR/unzipped/ -name '*.ZD2' -exec python3 ../decode_effect.py -d {} \; | grep -A 3 "length" | grep '0000 ' | sort | uniq -c
1 0000 02 FA 90 8C 02 00 00 00 01 00 00 00 00 00 00 00 ................
1 0000 03 D6 EA 31 07 00 00 00 01 00 00 00 00 00 00 00 ...1............
1 0000 04 DB 8F 8F 07 00 00 00 01 00 00 00 00 00 00 00 ................
1 0000 06 47 DA 68 07 00 00 00 01 00 01 00 00 00 00 00 .G.h............
1 0000 07 44 34 BA 02 00 00 00 01 00 01 00 01 00 00 00 .D4.............
1 0000 08 29 C0 19 07 00 00 00 01 00 01 00 00 00 00 00 .)..............
1 0000 0D 6F 1F 31 07 00 00 00 01 00 01 00 01 00 00 00 .o.1............
1 0000 12 47 DD 99 07 00 00 00 01 00 00 00 00 00 00 00 .G..............
1 0000 18 3D 15 81 07 00 00 00 01 00 00 00 00 00 00 00 .=..............
1 0000 19 EB FF B4 07 00 00 00 01 00 01 00 01 00 00 00 ................
1 0000 1A 78 06 2A 02 00 00 00 01 00 00 00 00 00 00 00 .x.*............
1 0000 1C C6 96 5E 02 00 00 00 01 00 01 00 00 00 00 00 ...^............
1 0000 1D AC 20 08 02 00 00 00 01 00 01 00 00 00 00 00 .. .............
1 0000 1E A0 16 F5 07 00 00 00 01 00 01 00 00 00 00 00 ................
1 0000 1E A1 BC 59 07 00 00 00 01 00 00 00 00 00 00 00 ...Y............
1 0000 1E DF 86 B4 07 00 00 00 01 00 00 00 00 00 00 00 ................
1 0000 1E EE 8E 05 02 00 00 00 01 00 00 00 00 00 00 00 ................
1 0000 22 6F F6 A2 07 00 00 00 01 00 01 00 01 00 00 00 "o..............
1 0000 22 81 10 45 07 00 00 00 01 00 01 00 01 00 00 00 "..E............
1 0000 28 57 E5 3D 06 00 00 00 01 00 01 00 00 00 00 00 (W.=............
1 0000 29 C9 B6 85 07 00 00 00 01 00 01 00 01 00 00 00 )...............
1 0000 2C 29 9D 43 07 00 00 00 01 00 00 00 00 00 00 00 ,).C............
1 0000 2C 55 BB 05 07 00 00 00 01 00 01 00 00 00 00 00 ,U..............
1 0000 2D 42 7F D3 07 00 00 00 01 00 01 00 00 00 00 00 -B.............
1 0000 2D DF 99 BB 07 00 00 00 01 00 01 00 01 00 00 00 -...............
1 0000 33 55 4E FF 07 00 00 00 01 00 01 00 00 00 00 00 3UN.............
1 0000 36 1E BD 6D 07 00 00 00 01 00 01 00 01 00 00 00 6..m............
1 0000 39 AF 48 30 02 00 00 00 01 00 01 00 00 00 00 00 9.H0............
1 0000 3B 3C 05 3D 07 00 00 00 01 00 01 00 00 00 00 00 ;<.=............
1 0000 3C 8C 56 58 07 00 00 00 01 00 00 00 00 00 00 00 <.VX............
1 0000 3D 53 A8 B3 07 00 00 00 01 00 01 00 00 00 00 00 =S..............
1 0000 3D F4 B6 F5 07 00 00 00 01 00 01 00 00 00 00 00 =...............
1 0000 3E 7D 7E E4 07 00 00 00 01 00 01 00 01 00 00 00 >}~.............
1 0000 43 76 92 81 07 00 00 00 01 00 00 00 00 00 00 00 Cv..............
1 0000 44 7A 7F 83 07 00 00 00 01 00 01 00 01 00 00 00 Dz.............
1 0000 44 B5 E1 61 07 00 00 00 01 00 01 00 01 00 00 00 D..a............
1 0000 49 CB 71 D1 07 00 00 00 01 00 01 00 01 00 00 00 I.q.............
1 0000 4A 51 8A 3C 02 00 00 00 01 00 00 00 00 00 00 00 JQ.<............
1 0000 4B 58 2D E7 07 00 00 00 01 00 01 00 00 00 00 00 KX-.............
1 0000 50 D1 FE 33 07 00 00 00 01 00 01 00 00 00 00 00 P..3............
1 0000 53 DD 07 30 07 00 00 00 01 00 01 00 01 00 00 00 S..0............
1 0000 55 ED 8C 50 02 00 00 00 01 00 00 00 00 00 00 00 U..P............
1 0000 56 65 DE C1 07 00 00 00 01 00 01 00 01 00 00 00 Ve..............
1 0000 58 CB D4 A3 02 00 00 00 01 00 00 00 00 00 00 00 X...............
1 0000 59 16 9A FD 02 00 00 00 01 00 00 00 00 00 00 00 Y...............
1 0000 59 AE 0D 19 02 00 00 00 01 00 01 00 00 00 00 00 Y...............
1 0000 59 D2 48 0C 07 00 00 00 01 00 00 00 00 00 00 00 Y.H.............
1 0000 59 DB 3A 1A 02 00 00 00 01 00 01 00 01 00 00 00 Y.:.............
1 0000 5B D1 75 30 06 00 00 00 01 00 01 00 00 00 00 00 [.u0............
1 0000 5C B3 09 36 07 00 00 00 01 00 01 00 01 00 00 00 \..6............
1 0000 5E 7F 04 EC 02 00 00 00 01 00 01 00 01 00 00 00 ^..............
1 0000 5E B1 BD E3 06 00 00 00 01 00 01 00 00 00 00 00 ^...............
1 0000 60 14 22 2B 02 00 00 00 01 00 01 00 01 00 00 00 `."+............
1 0000 61 3A 95 04 07 00 00 00 01 00 01 00 00 00 00 00 a:..............
1 0000 61 E4 56 DD 07 00 00 00 01 00 00 00 01 00 00 00 a.V.............
1 0000 64 A8 EB 84 07 00 00 00 01 00 00 00 00 00 00 00 d...............
1 0000 68 30 2E D3 07 00 00 00 01 00 00 00 00 00 00 00 h0..............
1 0000 6C F1 56 23 07 00 00 00 01 00 01 00 00 00 00 00 l.V#............
1 0000 73 75 98 13 07 00 00 00 01 00 01 00 01 00 00 00 su..............
1 0000 74 79 D2 27 07 00 00 00 01 00 01 00 00 00 00 00 ty.'............
1 0000 74 F2 C4 40 06 00 00 00 01 00 01 00 00 00 00 00 t..@............
1 0000 79 42 A6 A8 02 00 00 00 01 00 00 00 00 00 00 00 yB..............
1 0000 7A 00 70 73 07 00 00 00 01 00 00 00 00 00 00 00 z.ps............
1 0000 80 7D C7 1A 02 00 00 00 01 00 00 00 00 00 00 00 .}..............
1 0000 82 D1 C2 F1 07 00 00 00 01 00 00 00 00 00 00 00 ................
1 0000 82 D9 35 C7 07 00 00 00 01 00 01 00 00 00 00 00 ..5.............
1 0000 87 F4 D8 B2 07 00 00 00 01 00 01 00 00 00 00 00 ................
1 0000 88 10 4B DA 07 00 00 00 01 00 01 00 00 00 00 00 ..K.............
1 0000 88 86 E7 48 07 00 00 00 01 00 01 00 01 00 00 00 ...H............
1 0000 8A 04 63 AC 07 00 00 00 01 00 01 00 00 00 00 00 ..c.............
1 0000 93 77 BC 89 07 00 00 00 01 00 01 00 00 00 00 00 .w..............
1 0000 97 15 22 A3 07 00 00 00 01 00 01 00 00 00 00 00 ..".............
1 0000 97 27 78 E6 07 00 00 00 01 00 00 00 00 00 00 00 .'x.............
1 0000 9A D0 49 76 07 00 00 00 01 00 01 00 01 00 00 00 ..Iv............
1 0000 9B 51 01 5D 07 00 00 00 01 00 01 00 01 00 00 00 .Q.]............
1 0000 9C 40 F7 EB 07 00 00 00 01 00 01 00 00 00 00 00 .@..............
1 0000 9D 3E 64 C0 02 00 00 00 01 00 00 00 00 00 00 00 .>d.............
1 0000 9E E1 60 A0 07 00 00 00 01 00 00 00 00 00 00 00 ..`.............
1 0000 A0 46 8A 4D 06 00 00 00 01 00 01 00 00 00 00 00 .F.M............
1 0000 A1 AD FD DE 07 00 00 00 01 00 01 00 01 00 00 00 ................
1 0000 A2 76 BE 5C 07 00 00 00 01 00 01 00 00 00 00 00 .v.\............
1 0000 A3 92 39 ED 07 00 00 00 01 00 00 00 00 00 00 00 ..9.............
1 0000 A8 CF 22 71 07 00 00 00 01 00 01 00 00 00 00 00 .."q............
1 0000 AC 63 90 7E 07 00 00 00 01 00 01 00 00 00 00 00 .c.~............
1 0000 AD 31 82 D9 07 00 00 00 01 00 00 00 00 00 00 00 .1..............
1 0000 AD E6 AF EF 07 00 00 00 01 00 00 00 00 00 00 00 ................
1 0000 AE 97 88 44 07 00 00 00 01 00 01 00 00 00 00 00 ...D............
1 0000 B2 05 FC 60 02 00 00 00 01 00 01 00 00 00 00 00 ...`............
1 0000 B3 EF C4 50 07 00 00 00 01 00 01 00 00 00 00 00 ...P............
1 0000 B5 BB E2 99 02 00 00 00 01 00 00 00 00 00 00 00 ................
1 0000 B6 35 D8 5D 02 00 00 00 01 00 00 00 00 00 00 00 .5.]............
1 0000 B8 A0 ED 32 07 00 00 00 01 00 01 00 01 00 00 00 ...2............
1 0000 B9 E1 F5 34 07 00 00 00 01 00 00 00 00 00 00 00 ...4............
1 0000 BB 56 30 E9 07 00 00 00 01 00 01 00 00 00 00 00 .V0.............
1 0000 BE B4 92 B7 07 00 00 00 01 00 00 00 01 00 00 00 ................
1 0000 C0 AE 22 11 02 00 00 00 01 00 00 00 00 00 00 00 ..".............
1 0000 C1 25 A6 72 07 00 00 00 01 00 00 00 00 00 00 00 .%.r............
1 0000 C6 68 92 99 06 00 00 00 01 00 01 00 01 00 00 00 .h..............
1 0000 C8 24 8A DE 02 00 00 00 01 00 01 00 01 00 00 00 .$..............
1 0000 C8 B7 80 65 07 00 00 00 01 00 01 00 00 00 00 00 ...e............
1 0000 C9 CC 02 71 07 00 00 00 01 00 01 00 01 00 00 00 ...q............
1 0000 CB 3D 75 3D 02 00 00 00 01 00 01 00 00 00 00 00 .=u=............
1 0000 CE DB 2E DB 07 00 00 00 01 00 00 00 00 00 00 00 ................
1 0000 CF 2F E2 57 07 00 00 00 01 00 00 00 00 00 00 00 ./.W............
1 0000 CF 49 EF 99 07 00 00 00 01 00 00 00 00 00 00 00 .I..............
1 0000 D0 19 4F 8F 07 00 00 00 01 00 01 00 00 00 00 00 ..O.............
1 0000 D1 1F 46 39 07 00 00 00 01 00 00 00 00 00 00 00 ..F9............
1 0000 D4 12 69 ED 07 00 00 00 01 00 01 00 00 00 00 00 ..i.............
1 0000 D5 64 6A 51 06 00 00 00 01 00 01 00 00 00 00 00 .djQ............
1 0000 D7 7C 43 2A 07 00 00 00 01 00 01 00 01 00 00 00 .|C*............
1 0000 DA 1D AC 76 07 00 00 00 01 00 00 00 00 00 00 00 ...v............
1 0000 DC 89 DC D8 07 00 00 00 01 00 01 00 00 00 00 00 ................
1 0000 DD D2 E1 5A 07 00 00 00 01 00 00 00 00 00 00 00 ...Z............
1 0000 DE FF F2 7E 02 00 00 00 01 00 00 00 00 00 00 00 ...~............
1 0000 E3 04 E6 48 07 00 00 00 01 00 00 00 00 00 00 00 ...H............
1 0000 E4 AD 9D 5C 07 00 00 00 01 00 01 00 00 00 00 00 ...\............
1 0000 E5 A7 E0 B9 07 00 00 00 01 00 00 00 01 00 00 00 ................
1 0000 E6 0D A2 91 02 00 00 00 01 00 01 00 00 00 00 00 ................
1 0000 E6 51 3B 7B 07 00 00 00 01 00 00 00 00 00 00 00 .Q;{............
1 0000 E7 8D 4B 80 07 00 00 00 01 00 00 00 00 00 00 00 ..K.............
1 0000 EC 50 AB 3D 07 00 00 00 01 00 01 00 00 00 00 00 .P.=............
1 0000 EF 75 65 84 02 00 00 00 01 00 01 00 00 00 00 00 .ue.............
1 0000 F3 EB 0F 72 07 00 00 00 01 00 01 00 01 00 00 00 ...r............
1 0000 F4 02 F8 22 07 00 00 00 01 00 01 00 00 00 00 00 ..."............
1 0000 F6 08 D4 02 07 00 00 00 01 00 01 00 00 00 00 00 ................
1 0000 F6 2D B0 B3 06 00 00 00 01 00 01 00 00 00 00 00 .-..............
1 0000 F8 18 0A C9 07 00 00 00 01 00 01 00 00 00 00 00 ................
1 0000 F9 7D 83 4D 07 00 00 00 01 00 01 00 01 00 00 00 .}.M............
1 0000 FB 96 86 E9 07 00 00 00 01 00 00 00 00 00 00 00 ................
1 0000 FC E2 14 F3 07 00 00 00 01 00 01 00 00 00 00 00 ................
Also note that the values you mentioned are followed by a byte, for the different versions of Air this is either 03 or 07 which is with an extra bit set... would be interesting to figure out what that means too.
I was looking for something that denotes whether an effect is mono/stereo for the input/output.
0x02: 0b0000 0010
0x03: 0b0000 0011
0x07: 0b0000 0111
It does seem like a bit-field or perhaps a part of the bigger bit-field. Looks like in your sorted sample 0x07 is more prevalent.
'Air' is used pretty on every pedal.
Actually, it's listed for most but not all -- it's not listed directly for B6, H8, R20, A1 D, A1X D; the latter two have no effects at all listed in the 7-list.
If those 4 bytes are a CRC32, then it's possible to brute force by calculating CRC for different sections/lengths and comparing. I previously did this on another project.
crc_find.py.txt crc_find2.py.txt
Note: there are different CRC32 methods, but 'crcmod' can handle them all.
Confirmed, these are a CRC32 checksum. Of the Bytes 12 through to -16 bytes from end of file. I'll add this functionality to the main code. crc_check.py.txt
v1.5$ python3 crc_check.py
00000000: 5A 44 4C 46 78 00 00 00 19 EB FF B4 07 00 00 00 ZDLFx...........
None
Stated checksum 0xb4ffeb19
inverted 0x4b0014e6
Inverted Match @ 4B0014E6
v1.4$ python3 ../v1.5/crc_check.py
00000000: 5A 44 4C 46 78 00 00 00 89 4B 53 4B 03 00 00 00 ZDLFx....KSK....
None
Stated checksum 0x4b534b89
inverted 0xb4acb476
Inverted Match @ B4ACB476
Done, can we close this bug?
v1.4$ python3 ../../decode_effect.py -V -o temp.zd2 -v AIR.ZD2
Checksum Validated: 0x4b534b89
Checksum Recalculated: 0x4b534b89
v1.5$ python3 ../../decode_effect.py -V -o temp.zd2 -v AIR.ZD2
Checksum Validated: 0xb4ffeb19
Checksum Recalculated: 0xb4ffeb19
Seems not all the effects pass the checksum validation....
$ grep -A 1 "Invalid" checksum_validation.txt
Checksum Invalid: 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./A1 FOUR/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./A1X FOUR/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: 0xa0d735f6
0x0b000030 : ChromeWah (v1.50, 6.97%), ./A1X FOUR/unzipped/CHRM_WAH.ZD2
--
Checksum Invalid: 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./G1X FOUR/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: 0xa0d735f6
0x0b000030 : ChromeWah (v1.50, 6.97%), ./G1X FOUR/unzipped/CHRM_WAH.ZD2
--
Checksum Invalid: 0x1f67920a
0x05000018 : MS4x12GB (v1.30, 9.02%), ./G1X FOUR/unzipped/MS4X12GB.ZD2
--
Checksum Invalid: 0x2384e91e
0x0500002b : FD MA2x12 (v1.30, 9.10%), ./G1X FOUR/unzipped/FDMA2X12.ZD2
--
Checksum Invalid: 0x8b69af12
0x05000040 : MK1 1x12 (v1.30, 8.84%), ./G1X FOUR/unzipped/MK1_1X12.ZD2
--
Checksum Invalid: 0xc8a2c0bc
0x030000f0 : BG GRID (v1.30, 16.40%), ./G1X FOUR/unzipped/BG_GRID.ZD2
--
Checksum Invalid: 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./G11/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: 0xa0d735f6
0x0b000030 : ChromeWah (v1.50, 6.97%), ./G11/unzipped/CHRM_WAH.ZD2
--
Checksum Invalid: 0x1f67920a
0x05000018 : MS4x12GB (v1.30, 9.02%), ./G11/unzipped/MS4X12GB.ZD2
--
Checksum Invalid: 0x2384e91e
0x0500002b : FD MA2x12 (v1.30, 9.10%), ./G11/unzipped/FDMA2X12.ZD2
--
Checksum Invalid: 0x8b69af12
0x05000040 : MK1 1x12 (v1.30, 8.84%), ./G11/unzipped/MK1_1X12.ZD2
--
Checksum Invalid: 0xb4385f36
0x06000170 : Duo Phase (v1.10, 9.84%), ./G11/unzipped/DUO_PHA.ZD2
--
Checksum Invalid: 0xc8a2c0bc
0x030000f0 : BG GRID (v1.30, 16.40%), ./G11/unzipped/BG_GRID.ZD2
--
Checksum Invalid: 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./B1X FOUR/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./G1 FOUR/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: 0x1f67920a
0x05000018 : MS4x12GB (v1.30, 9.02%), ./G1 FOUR/unzipped/MS4X12GB.ZD2
--
Checksum Invalid: 0x2384e91e
0x0500002b : FD MA2x12 (v1.30, 9.10%), ./G1 FOUR/unzipped/FDMA2X12.ZD2
--
Checksum Invalid: 0x8b69af12
0x05000040 : MK1 1x12 (v1.30, 8.84%), ./G1 FOUR/unzipped/MK1_1X12.ZD2
--
Checksum Invalid: 0xc8a2c0bc
0x030000f0 : BG GRID (v1.30, 16.40%), ./G1 FOUR/unzipped/BG_GRID.ZD2
--
Checksum Invalid: 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./B1 FOUR/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./G3n/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: 0xa0d735f6
0x0b000030 : ChromeWah (v1.50, 6.97%), ./G3n/unzipped/CHRM_WAH.ZD2
--
Checksum Invalid: 0x1f67920a
0x05000018 : MS4x12GB (v1.30, 9.02%), ./G3n/unzipped/MS4X12GB.ZD2
--
Checksum Invalid: 0x2384e91e
0x0500002b : FD MA2x12 (v1.30, 9.10%), ./G3n/unzipped/FDMA2X12.ZD2
--
Checksum Invalid: 0x8b69af12
0x05000040 : MK1 1x12 (v1.30, 8.84%), ./G3n/unzipped/MK1_1X12.ZD2
--
Checksum Invalid: 0xb4385f36
0x06000170 : Duo Phase (v1.10, 9.84%), ./G3n/unzipped/DUO_PHA.ZD2
--
Checksum Invalid: 0xc8a2c0bc
0x030000f0 : BG GRID (v1.30, 16.40%), ./G3n/unzipped/BG_GRID.ZD2
--
Checksum Invalid: 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./R20/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: 0x1f67920a
0x05000018 : MS4x12GB (v1.30, 9.02%), ./R20/unzipped/MS4X12GB.ZD2
--
Checksum Invalid: 0x2384e91e
0x0500002b : FD MA2x12 (v1.30, 9.10%), ./R20/unzipped/FDMA2X12.ZD2
--
Checksum Invalid: 0x8b69af12
0x05000040 : MK1 1x12 (v1.30, 8.84%), ./R20/unzipped/MK1_1X12.ZD2
--
Checksum Invalid: 0xc8a2c0bc
0x030000f0 : BG GRID (v1.30, 16.40%), ./R20/unzipped/BG_GRID.ZD2
--
Checksum Invalid: 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./B3n/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./G6/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: 0xa0d735f6
0x0b000030 : ChromeWah (v1.50, 6.97%), ./G6/unzipped/CHRM_WAH.ZD2
--
Checksum Invalid: 0x1f67920a
0x05000018 : MS4x12GB (v1.30, 9.02%), ./G6/unzipped/MS4X12GB.ZD2
--
Checksum Invalid: 0x2384e91e
0x0500002b : FD MA2x12 (v1.30, 9.10%), ./G6/unzipped/FDMA2X12.ZD2
--
Checksum Invalid: 0x8b69af12
0x05000040 : MK1 1x12 (v1.30, 8.84%), ./G6/unzipped/MK1_1X12.ZD2
--
Checksum Invalid: 0xc8a2c0bc
0x030000f0 : BG GRID (v1.30, 16.40%), ./G6/unzipped/BG_GRID.ZD2
--
Checksum Invalid: should be 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./G5n/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: should be 0xa0d735f6
0x0b000030 : ChromeWah (v1.50, 6.97%), ./G5n/unzipped/CHRM_WAH.ZD2
--
Checksum Invalid: should be 0x1f67920a
0x05000018 : MS4x12GB (v1.30, 9.02%), ./G5n/unzipped/MS4X12GB.ZD2
--
Checksum Invalid: should be 0x2384e91e
0x0500002b : FD MA2x12 (v1.30, 9.10%), ./G5n/unzipped/FDMA2X12.ZD2
--
Checksum Invalid: should be 0x8b69af12
0x05000040 : MK1 1x12 (v1.30, 8.84%), ./G5n/unzipped/MK1_1X12.ZD2
--
Checksum Invalid: should be 0xb4385f36
0x06000170 : Duo Phase (v1.10, 9.84%), ./G5n/unzipped/DUO_PHA.ZD2
--
Checksum Invalid: should be 0xc8a2c0bc
0x030000f0 : BG GRID (v1.30, 16.40%), ./G5n/unzipped/BG_GRID.ZD2
--
Checksum Invalid: should be 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./H8/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: should be 0x1f67920a
0x05000018 : MS4x12GB (v1.30, 9.02%), ./H8/unzipped/MS4X12GB.ZD2
--
Checksum Invalid: should be 0x2384e91e
0x0500002b : FD MA2x12 (v1.30, 9.10%), ./H8/unzipped/FDMA2X12.ZD2
--
Checksum Invalid: should be 0x8b69af12
0x05000040 : MK1 1x12 (v1.30, 8.84%), ./H8/unzipped/MK1_1X12.ZD2
--
Checksum Invalid: should be 0xc8a2c0bc
0x030000f0 : BG GRID (v1.30, 16.40%), ./H8/unzipped/BG_GRID.ZD2
--
Checksum Invalid: should be 0x3c4ebb35
0x01000080 : OptComp (v1.50, 12.72%), ./G3Xn/unzipped/OPTCOMP.ZD2
--
Checksum Invalid: should be 0xa0d735f6
0x0b000030 : ChromeWah (v1.50, 6.97%), ./G3Xn/unzipped/CHRM_WAH.ZD2
--
Checksum Invalid: should be 0x1f67920a
0x05000018 : MS4x12GB (v1.30, 9.02%), ./G3Xn/unzipped/MS4X12GB.ZD2
--
Checksum Invalid: should be 0x2384e91e
0x0500002b : FD MA2x12 (v1.30, 9.10%), ./G3Xn/unzipped/FDMA2X12.ZD2
--
Checksum Invalid: should be 0x8b69af12
0x05000040 : MK1 1x12 (v1.30, 8.84%), ./G3Xn/unzipped/MK1_1X12.ZD2
--
Checksum Invalid: should be 0xb4385f36
0x06000170 : Duo Phase (v1.10, 9.84%), ./G3Xn/unzipped/DUO_PHA.ZD2
--
Checksum Invalid: should be 0xc8a2c0bc
0x030000f0 : BG GRID (v1.30, 16.40%), ./G3Xn/unzipped/BG_GRID.ZD2
...Confirmed, these are a CRC32 checksum. Of the Bytes 12 through to -16 bytes from end of file. I'll add this functionality to the main code.
Nice find. Can you give an explicit example of the matching bytes and the CRC32 result? Say, you can use any of the AIR.ZD2 versions.
In general this indeed could be the case, as the trailing 16 bytes of ZD2 are the ones which are also differing between the versions of the effect's ZD2. However, while these are different between v1.30 and v1.40, these trailing bytes are the same between v1.40 and v1.50.
| filename | version | trailing bytes [0x3B5D-0x3B6C] |
|---|---|---|
| AIR.ZD2 | v1.50 | [29 23 BE 84 E1 6C D6 AE 52 90 49 F1 F1 BB E9 EB] |
| AIR.ZD2 | v1.40 | [29 23 BE 84 E1 6C D6 AE 52 90 49 F1 F1 BB E9 EB] |
| AIR.ZD2 | v1.30 | [5F C5 17 C5 3E FC 33 63 C3 84 92 AB 08 A3 AA 3F] |
I tried to make sense out of the CRC32 matching you've done just to understand the actual values in ZD2 that match.
To recap:
- ZD2 file is split into 3 parts:
- head:
[0x00:0x0b], the last 4-bytes store acrc32_checksumvalue - body:
[0x0c:(end-0x10)] - tail:
[(end-0x0F):end], the last 16-bytes of the ZD2 file
- CRC32 checksum is calculated over the body
- resulting CRC32 checksum value is inverted:
crcValue ^ 0xFFFFFFFF - the inverted CRC32 value is matching the 4-byte integer at the end of header section:
crc32_checksum
tail -c +13 -${version}/${zd2_file} | head -c -16 > zd2_body.bin
crc32 zd2_body.bin
For "AIR.ZD2" effect this yields:
| filename | version | bytes [0x8:0xB] | body [0x0C:(end-0x10)] | CRC32(body) | CRC32 ^0xFFFFFFFF |
|---|---|---|---|---|---|
| AIR.ZD2 | v1.50 | [19 EB FF B4] |
[07 ... 0A] |
0x4B0014E6 |
0xB4FFEB19 |
| AIR.ZD2 | v1.40 | [89 4B 53 4B] |
[03 ... 0A] |
0xB4ACB476 |
0x4B534B89 |
| AIR.ZD2 | v1.30 | [D3 19 D6 C4] |
[03 ... 0A] |
0x3B29E62C |
0xC4D619D3 |
... Seems not all the effects pass the checksum validation
I looked into OPTCOMP.ZD2 versions.
Curiously, two recent versions (1.40, 1.50) list the same values in the checksum field ([f9 7d 83 4d]), yet these have different inverted-CRC32 checksum for their "body" (0x490f713c, 0x3c4ebb35). Neither matches. While the checksums in the file version 1.30 seem to match according to the algorithm above.
The only two parts where the v1.40 and v1.50 differ are the version string and the first byte of the "body" ( 0x03 vs. 0x07) which, as we established, seems to be some kind of bit-field.
Similar situation is with MS4X12GB.ZD2 (v1.20 vs. 1.30)
colordiff -y <(xxd v1.20/MS4X12GB.ZD2) <(xxd v1.30/MS4X12GB.ZD2)
00000000: 5a44 4c46 7800 0000 cf2f e257 0300 0000 ZDLFx..../ | 00000000: 5a44 4c46 7800 0000 cf2f e257 0700 0000 ZDLFx..../
00000010: 0100 0000 0000 0000 8000 0000 0000 0000 .......... 00000010: 0100 0000 0000 0000 8000 0000 0000 0000 ..........
...
00000050: 0000 0000 0000 0000 0131 2e32 3000 0005 .........1 | 00000050: 0000 0000 0000 0000 0131 2e33 3000 0005 .........1
Not sure if this is just a human edit error or the algorithm above takes some additional details. As an idea, you may try to check if all of the mismatching effects/versions as well have 0x07 value following the checksum bytes.
Your understanding of the CR32 coding is correct.
Further the body is split in to the sections which start with the markers "ICON", "TXJ1", "TXE1", "INFO", "DATA", "PRMJ" and "PRME".
I pushed a couple of quick changes to help experimentation, though since I was already creating ZD2 by patching others together I don't think that the pedal actually checks the CRC32. Since we know about it, it's better to correct the parameter when writing ZD2 file....
I also suspect that the incorrect CRC32 seen in the official ZD2 is some sloppiness within Zoom. Maybe they had to fix something, and took a shortcut?
While most of the "Invalid" have 07, a couple have 05. And there are lots of "Valid" which have 07. I don't think these things are connected.
checksum_validation.txt
Well, 0x05 and 0x07 both have the upper bit set, unlike 0x03. It's quite possible that the upper bit describes the type of the update. In those cases that have 0x07 (that I checked) the update introduced by the version was just the version number bump, that is there was no actual code/description changes. Meanwhile, versions with 0x03 (or lower??) do have differences in the code sections.
In that sense, the checksum may be directly pointing to the version of the effect's code, almost like a version-control hash. Though it's not clear why would one want to promote the version number without actual code changes.
When I mentioned that maybe Zoom took a shortcut, I meant that maybe an engineer just fixed an issue with the data by hand editing the file (or maybe skipped some part of the process to re-create the checksum).... these things happen in production.
I'm not convinced that changing the parts of the file that the CRC32 applies would have any benefit. I can run the same "find the checksum-ed block" test on a Invalid checksum, to see if it's another block of the file... I doubt it.
I'm under the impression that sections of the ZD2 (other than 'code'), are actually just for GuitarLab to do it's thing (display ICON, description, etc). I don't know whether the pedal actually does anything with them.... can check by changing and seeing if pedal behavior remains the same.