Why is it so difficult to shift subtitles on Blu-ray?
Although it is possible to shift subtitles on DVD, this is much more difficult on Blu-ray. Subtitles are part of the “protected video path” which is cryptographically protected. A vendor would need permission and certified code from the BDA to break into the path and adjust the subtitles. So far, this support has not been forthcoming. It is another consequence of Digital Rights Management. Since subtitles occupy a tiny amount of disc space, the studios could easily provide alternative subtitle tracks shifted into the image area, but this practice has not been widely adopted. Immortal Beloved is a title that does it this way.
