One of the biggest, conceptual changes introduced with Blu-ray discs (and continued with UHD Blu-ray discs) was the idea the Studio could include computer program code -- software -- ON the disc, which would load and run whenever you played that disc, and which would CONTROL that playback.  No longer would disc playback be strictly limited to the "user interface" features implemented by each, different, Blu-ray player!  So long as the player could run the on-disc software, the DISC could invent its OWN user interface!  There was nothing like this for prior, SD-DVD discs.

This on-disc software would be written in a variant of the Java programming language to be called "BD-J" (Blu-ray Disc Java).  The expectations for how Studios would use BD Java were truly grand -- to begin with.  All sorts of fancy features were proposed to "enhance" the customer value of these discs.  The actual result has been rather a mixed bag.  In particular, some Studios seem to be most keen on how BD Java can be used to make a disc really difficult to copy -- something which has NOTHING to do with the customer’s experience.

In this post I'll talk about BD Java, and how it relates to the perennial complaint: My disc player won't let me do Resume Play on my movie!