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BD-R with UDF filesystem (Miscellaneous)

posted by Zyzzle, 22.12.2020, 04:44

> If you're wanting to read movie files from BD's, you're correct that the
> files sizes can be huge (far greater than FAT32 can handle). I was
> thinking more along the lines of using a BD (or DVD or CD) as a backup
> mechanism, or even a way to transfer files between computers. I don't know
> of a DOS program that will play BD movies (and I doubt that there ever will
> be one), but if you are treating a BD simply as a media storage device (and
> don't really care about the formatting) I think you could create something
> roughly equivalent to the DISKCOPY program that could copy the entire disk.
> Optical media has sectors much like magnetic media, though optical media
> is designed to be written serially rather than randomly, though I don't
> think it necessarily NEEDS to be that way.
>
> Another possibility is exFAT, though that is considered proprietary by MS.
> The point is that you don't need to limit yourself to UDF just because
> everybody else does -- I think FAT32 or exFAT would work just fine on
> optical media (but I could be wrong). However, you cannot simply treat it
> like a "big floppy" since you can only write a limited number of times to
> the disk, and every time you write a file you also need to modify the FAT.
> That's one of the ways that DVD-RAM is superior to the other optical
> alternaitves -- you can reliably write to a DVD-RAM many more times than
> you can other optical media. Essentially, you can treat a DVD-RAM as a
> really big floppy.
Khusraw's DOS port of MPLAYER can play (unencypted) Blu-ray discs, but only if formatted in ISO9660 standard, as there's no UDF driver. The problem is in MS-DOS, filesizes > 2GB aren't readable due to signed longint limitation.

There's an experimental exFAT reader for DOS as well, but the problem again is that filesizes > 2GB aren't readable, so that completely defeats the purpose of having an exFAT driver in the first place. The raw assembly code of MSDOS.SYS and / or IO.SYS needs to be modified somehow. Even if possible, I do not know if filesizes > 4GB can be directly supported.

Same issues for the R. Loew drivers (I think?), or did he somehow magically erase and / or patch the 32-bit longint limitations on filesizes as well as increase sector sizes and capacities of drives beyond the 2TB limit? I'm not sure, as I've not personally tested those drivers.

Backporting a *nix UDF driver to MS-DOS might work, if such a driver exists. I think by now, UDF standard isn't going to change very much. I think v. 2.6 is available now, but BD-Rs are written in v 2.5 anyway.

Thanks very much for pointing out how to patch MSDOS.sys file to support > 512 byte sector sizes. I figured it was probably a two-byte patch, but didn't know exactly *where* to patch, as I hadn't studied the code closely.

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