Hit a couple snags, the zlib compression in esp/esm seems different.
That and the BSA format seems to have changed and Visilli's BSA Commander
doesn't work.

Interestingly, BSA Commander seems to work for packing bsa files. I've used it to pack and the files work fine in Fallout 3.

However, when I couldn't extract from Fallout 3's own bsa files, I turned to FOMM.

There's no change in the esm compression; the only format change is an extra 4 bytes in each group and record header. The rest is just changes to the contents of records.

Fallout can read oblivion format bsa's. Fallout format bsa's have a higher version number in their header (0x68 instead of 0x67) and a few of the flags have different meanings. In particular there's one flag which means that complete file names are stored at the start of the each file data block in addition to the usual separate folder and file name blocks. (Used by the vanilla textures bsa.) bsa commander refuses to open the bsa when it hits the increased version number, but if you hex edit it back to 0x67 then it'll open everything except for the textures bsa.

Why not just use FOMM for packing and unpacking the fallout BSA's? Or is there something I missed?

Not really, just commenting on the (lack of) differences between the oblivion and fallout formats.

Here is the definition of the record header for FO3:

  wbMainRecordHeader := wbStruct('Record Header', [	wbString('Signature', 4, cpCritical),	wbInteger('Data Size', itU32, nil, cpIgnore),	wbRecordFlags,	wbFormID('FormID', cpCritical),	wbByteArray('Version Control Info 1', 4, cpIgnore),	wbInteger('Form Version', itU16, nil, cpBenign),	wbByteArray('Version Control Info 2', 2, cpIgnore)  ]);

The 4 bytes at the end are new. The first 2 bytes are a record version number, the next 2 are used as flags for Beth's VCS (just like the 4 bytes in front which already existed in TES4).

The current version for all record types as it's currently saved by GECK seems to be 15. But Fallout3.esm contains records with pretty much all version numbers between 0 and 15 (and older versions usually have some structural differences to version 15 records of the same type).

Awesome. I've been really hanging out for a one-click packaging tool for FO3. TES4FILES was great and easy to use. Can't wait to get FO3FILES

Oh thank god, you are doing this. I was thinking of asking about it, but now I don't have to.

:wub:

New release V3.3 of TES4Files has "beta fallout3 support"....

:twirl:

I realize it's beta support, but I just wanted to report that it misses textures/interface/icons/ and shellcasing nifs. Thanks very much MentalElf!