PSISOIMG0000

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ISO.BIN structure

All offsets are in little endian (except in the last table where there are two counters in decimal) 

1 block = 1024 bytes (0x400)
1 cluster = 16 blocks = 1024*16 bytes =16384 bytes (0x4000)

disc_starts ----------> 0x000400 (disc1), 0x100400 (disc2), 0x200400 (disc3), 0x300400 (disc4), etc...
disc_tocs -----------> 0x000C00 (disc1), 0x100C00 (disc2), 0x200C00 (disc3), 0x300C00 (disc4), etc...
disc_map_tables ----> 0x004400 (disc1), 0x104400 (disc2), 0x204400 (disc3), 0x304400 (disc4), etc...

Header (optional)

1 block = 1024 bytes (0x400)

Always exists in PS1 classic multidiscs (the example below is from ff8), in the official PS1 classics single disc doesnt exists, but the custom PS1 classics single discs can use it (there are custom tools that adds it in all cases)

Block Nº Offset Length Name Example Description
0
common_header		 0x0000 0x10 (16 bytes) magic PSTITLEIMG000000
0x0010 0x1F0 (496 bytes) padding
0x0200 0x64 (100 bytes) discs_start_offsets 00 04 00 00 25 chunks of 4 bytes ... each chunk = start position of each disc, in games with only 1 disc only the first 4 bytes are used
0x0264 0x10 (16 bytes) game_id _SLES_12345 common identifyer for all discs
0x0274 0x18C (396 bytes) padding

Section

64 clusters, 1024 blocks, 10485576 bytes (0x100000)

This structure is repeated one time for every disc of the game all them joined together consecutivelys (the example below is from ff8), the whole space is reserved even when there is no data used

Cluster Nº Block Nº Offset Length Name Example Notes
0
Disc map header		 1 0x0000 0x00C (12 bytes) magic PSISOIMG0000
0x000C 0x004 (4 bytes) section size Offset from the start of the PSISOIMG section to the next section
For uncompressed images this is usually 0x100000 + size of iso-image padded to 0x9300
If the disc contains CD-DA tracks then this number will also include all the ATRACK encoded audio that follows after the disk image.
0x0010 0x3F0 (1008 bytes) padding
2 0x0400 0x010 (16 bytes) disc id _SLES_12345 in games with several discs each disc has a different id
0x0410 0x14 (20 bytes) padding
0x0420 0x4 (4 bytes) ps1 config firmware 0x06070070 config revision in little endian.
0x0424 0x4 (4 bytes) ps1 config firmware 0x06060000 config revision in little endian.
0x0428 0x84 (132 bytes) ps1 configs 1 0x00104500 Ad hoc game configs in little endian. Single config is 4 bytes param.
0x04AC 0x84 (132 bytes) ps1 configs 2 0x00104500 Ad hoc game configs in little endian. Single config is 4 bytes param.
3 0x0800 0x3FС (1020 bytes) Disc toc table variable Table of content, like CUE sheet, supports upto 99 entries (102 entries total)
0x0BFC 0x004 (4 bytes) disc start offset 0x100000
4 0x0C00 0x400 (1024 bytes) Audio tracks table Datas of audio tracks (2-65). offset, size, and more
5 0x1000 0x220 (544 bytes) Audio tracks table Datas of audio tracks (66-99). offset, size, and more
0x122C 0x080 (128 bytes) unknown Memory card related, probably custom path for external card.
0x12AC 0x004 (4 bytes) unknown Latest POPS read value but never use it, maybe some leftover from older version.
0x12B0 0x004 (4 bytes) Libcrypt Magic Word 0x1234 Little endian. Magic word is used as an answer to COP0 BPC reads for libcrypt games.
0x12B4 0x004 (4 bytes) unknown Emulator test if value is greater than 0, but value itself is not used (works like bool).
0x12D4 0x004 (4 bytes) subchannel offset 0x100400 Offset to where subchannel data is stored. This is used with libcrypt.
0x12D8 0x004 (4 bytes) subchannel count 0x178 Number of subchannel blocks. Each block is 12 bytes.
0x12DC 0x124 (292 bytes) padding
6 0x1400 0x400 (1024 bytes) not used
7 0x1800 0x400 (1024 bytes) not used
8 0x1C00 0x400 (1024 bytes) not used
9 0x2000 0x400 (1024 bytes) not used
10 0x2400 0x400 (1024 bytes) not used
11 0x2800 0x400 (1024 bytes) not used
12 0x2C00 0x400 (1024 bytes) not used
13 0x3000 0x400 (1024 bytes) not used
14 0x3400 0x400 (1024 bytes) not used
15 0x3800 0x400 (1024 bytes) not used
16 0x3C00 0x010 (16 bytes) checksum 0x1CCE0033... It seems to be the checksum of this block, and because this block is always unused the checksum is always 1CCE003360C6E8A6B36A972D00EAFDBF
0x3C10 0x3F0 (1008 bytes) padding
1
Disc map table		 17 0x4000 variable Disc map table Divided in chunks of 32 bytes
Up to 32
Up to 64
Disc map table

Disc toc table

Entry structure:

Entry Nº Offset Length Name Example Notes
1 0x00 0x01 (1 byte) TYPE 0x41/0x01 entry flags
0x01 0x01 (1 byte) TNO 00 always zero
0x02 0x01 (1 byte) POINT 0xA0/0xA1/0xA2/0x01/0x02/0x03/etc increases
0x03 0x01 (1 byte) MIN varies decimal
0x04 0x01 (1 byte) SEC varies decimal
0x05 0x01 (1 byte) FRAME varies decimal
0x06 0x01 (1 byte) ZERO 00 always zero
0x07 0x01 (1 byte) PMIN varies decimal
0x08 0x01 (1 byte) PSEC varies decimal
0x09 0x01 (1 byte) PFRAME varies decimal
Up to 102 same structure than the previous entry

Audio tracks table

Entry structure:

Entry Nº Offset Length Name Example Notes
1 0x00 0x04 (4 bytes) offset
0x04 0x04 (4 bytes) size
0x08 0x04 (4 bytes) unknown_0 always zeroed
0x0C 0x04 (4 bytes) enc_key encryption key (or 0 if not encrypted)
Up to 98 same structure than the previous entry

The audio tracks themselves are raw ATRAC3 streams without a header. One way to create such blobs is to use the atracdenc encoder and strip of the first 0x60 bytes which is the header. The resulting blob is what the Audio tracks table entries will point to.

Disc map table

The table has an area reserved of 1032192 bytes. Divided in 32256 entries, of 32 bytes each entry. The number of used entryes in the file_table can vary (seems to be dependant of the .iso contents). The number of entries availables to store data is affected by a checksum (16 bytes) that is present only in the the last block of each cluster (in block nº16 of every cluster) When this checksum is between used entryes... his length is 32 bytes (it "steals" the area of one entry) Seems to be a checksum of this block... when the block is filled with zeroes the checksum is : 1CCE0033 60C6E8A6 B36A972D 00EAFDBF

The first 4 bytes of each entry (file offset from start of .iso root) increases for each entry in a amount of bytes determined by the previous entryes.... in other words... the second file in the .iso is displaced the number of bytes used by the first file... and the third file is displaced in a amount of bytes used by the addition of the sizes of first and second file

Entry Nº Offset Length Name Example Notes
1 0x00 0x04 (4 bytes) file_offset 0 file offset from start of .iso root (for the first entry is always 0)
0x04 0x02 (2 bytes) file_size variable this size determines the displacement of the next file (in the next entry)
0x06 0x02 (2 bytes) file_type ? 01 00 usually 1... and 0 for the last entry
0x08 0x10 (16 bytes) file_checksum variable First 16 bytes of the sha1 of the uncompressed data
0x18 0x08 (8 bytes) padding
Up to 32256 same structure than the previous entry

Common Disc table

Composed by a variable number of entries (depends of the number of files/folders inside the discs), 12 bytes each entry

Entry Nº Offset Length Name Example Notes
1 0x00 0x04 (4 bytes) file_offset ? 0 always increases
0x04 0x02 (2 bytes) file_type ? 01 01 always 01 01
0x06 0x03 (3 bytes) counter 1 some kind of counter, in decimal, always increases <-------- related with "sectors" inside the .iso ?
0x09 0x03 (3 bytes) counter 2 another counter, in decimal, always increases, its in relationship with the previous counter (this one is always 200 bytes bigger than the previous one)
Up to ? same structure than the previous entry

Subchannel data

This is data stored in separate .pgd in psar (0xED4 [0x12D4] in ISO header point to it if available), should be required only for games that use libcrypt protection (LC2 and higher). Header of decrypted file is FFFFFFFF 00000000 FFFFFFFF, end of file is marked by FFFFFFFF FFFFFFFF FFFFFFFF. Values are always 150 sectors lower than real disc sector (pregap?). Values are in little endian (sector only actually, others are 1 byte values). See section below for example code on how to generate this table.

Entry Nº Name Offset Size (bytes) Example Notes
1 or 2? Sector 0x00 4 Sector number - 150
Track Number 0x04 1 0x01 Always 0x01
Index 0x05 1 0x01 Always 0x01
Pmin(relative) 0x06 1
Psec(relative) 0x07 1
Pframe(relative) 0x08 1
Amin (Absolute) 0x09 1
Asec (Absolute) 0x0A 1
Aframe (Absolute) 0x0B 1
Up to 1024 or up to 1022? (minus header/footer) same structure than the previous entry
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