Language Unit codes

[peppi_le_piou]

English is 25966. I have seen in a dvd 65535 (en) sometimes, what exactly is this and why is it used instead of 25966.

[Alex_ander]

65535 is the default (not set, 'undefined' is 0) value of audio language and subtitle language system registers (it's maximum value for any register). This value can often be seen in PGC' pre-commands and it probably comes from templates some authoring applications use for settiing audio or subtitle track. If the setting is not used at all, that command remains with default setting (also can be used for resetting after playback).

[peppi_le_piou]

So then, if 65535 is used then does that mean that there will only be one language on that dvd and it will be that in which country the dvd was pressed?

[Alex_ander]

Most likely there's a single language unit (by country or undefined), but having multiple audio/subtitle languages is still possible there by manual selection (65535 may be used e.g. to reset selection in the end). Multiple language units are used (not too often) to force automatic language settings by 'preferred_language' rewritten from player setup data. In this case playback goes to a certain language unit where it then finds forced settings for audio and subtitle language settings.
Where do you see 65535 (for language unit, for audio or subtitle)? I mainly deal with DVDRemake, where specifically for a language unit (unlike audio/subtitle) the direct number is hidden.

[blutach]

If there is only one LU, then it matters not one bit how it is identified - that's the one which will play.

However, this does not mean that there is only one language on the DVD - there can be 8 audio streams and 32 subpicture ones in each VTS - this just means there's only one set of menus (although in a LU marked "en", you often find 3 or 4 sets of menus in different languages, reachable depending on the value of a gprm).

Regards