[libbluray-devel] BD-J on UDF/ISO cannot read BDMV/STREAM

[Shaya Potter]

This prevents titles that have java code that validate via a stream
file to fail-close

Tried Mercy Street Season 1 (PBS, BD-J with an obfuscated Xlet). From
older AnyDVD use I already knew the Java title is not needed for
playback in the usual sense: it mainly writes a few GPRs and hands off
to HDMV. On libbluray the disc would not play correctly.

After tracing the Xlet, the failure was a FileNotFoundException
opening a file under BDMV/STREAM (here 00019.m2ts). That read is what
the protection seemingly uses to decide whether to publish the real
episode GPRs or dummy values that play wrong obfuscated playlists.

On a directory mount, I believe this is invisible: cacheAll is off and
Java can FileInputStream the host path. On ISO/UDF, bluray.vfs.root is
the VFS cache, and VFSCache skips BDMV/STREAM (so I believe it does
not want to copy multi-GB .m2ts into /tmp). Java then never sees the
file, the Xlet "fails", and the menu plays the wrong titles.

Once STREAM was readable from Java (without copying the clip into the
cache), the Xlet wrote the proper GPRs and the title played.

Suggested fix: keep “do not cache STREAM,” but implement
exists/length/FileInputStream for uncached STREAM via disc I/O
(disc_open_path / BD_FILE_H) instead of hiding the path. Copying
STREAM into VFSCache is not a real fix (feature .m2ts would dump
gigabytes into the cache).

After figuring this out and having my hacked up libbluray, I only then
tested with the mounted version, with a clean libbluray, which also
worked (hence the comment above).

This might explain in general misbehaviors between iso playback and
mounted playback.