OBD:Raw and separate file formats
Unless mentioned otherwise, this is about the PC retail .raw files.
- When mentioned otherwise, this can be about the .sep files as well.
Chunk offsets
This applies for .sep files as well
Alignment
- Although this may not be strictly required by the engine, the offsets of all original chunks start at 32-byte multiples.
- This implies a slight loss of space, but the storage is somewhat tidier that way. Easier to manipulate in hex editors ^^
- OUP will probably continue to store data that way. Storing things the way Bungie did is a way to avoid surprises.
Null offset
- At the start of the .raw or .sep file, there are 32-bytes of garbage
- That way, all meaningful raw/sep chunks start at offsets strictly greater than 0.
- If that wasn't the case, the null value of a raw/sep link would be ambiguous.
Differences across versions
Different content
Language versions
In this case the main difference in the .raw is due to the SNDD files.
Extra level0 textures
The level0_Final.raw of older versions stores a few megabytes worth of "obsolete" textures.
Texture compression
Depending on the version, the amount of textures stored in a lossy compressed format can be "most" to "almost none".
- This leads to dramatic variations in size for the .raw (over 10% of the total amount of game content).
Gaps
The original .raw are not packed as a compact sequence of 32-byte-aligned chunks.
- There are gaps of various sizes in every level, totalling up to 2 megabytes per level.
Interestingly, those gaps seem to be the same across version, even if other content differs.
- The content of those gaps is detailed below.
Skybox mipmaps
Those gaps occur in every level after each of the 5 skybox textures. They're filled with zeroes.
- Their size matches that required to store MIP map generations of the preceding TXMP chunk.
Orphaned chunks
Those seem to be mostly .raw parts of existing resources, orphaned at some point by the appending of a new version to the .raw.
- The pointer in the .dat got redirected to the new version, and the old version was lost.
So, either duplicates of existing resources, or obsolete versions reflecting development.
TRAM
Not too many of those. Always 32 bytes long. Probably always the same type. Content checking should tell.
OSBD
A few of those in level 0. Nothing but duplicates?
SNDD
Those make the most of the gap space. There seems to be ore than duplicates in the case of the SNDD.