3D

(?<=\b[12]\d{3}\b).*\b((Blu[-]?ray|BD)?3D|((H(alf)?|F(ull)?).?)?(O(ver)?.?U(nder)?|S(ide)?[\W_]?B(y)?.?S(ide)?))\b

Matches 3D stereoscopic format tags in two branches.

1. 3D tag - matches 3D optionally prefixed with Bluray or BD.

2. Stereoscopic packing format - matches Over-Under and Side-by-Side tags with an optional size prefix.

• The prefix group (H(alf)?|F(ull)?) recognises Half/H and Full/F as size indicators. The entire prefix is optional, so bare formats like SBS or OU match without one. Each optional suffix (alf, ull, ver, nder, ide, y) allows both short and long forms to match from a single pattern, e.g. O(ver)?.?U(nder)? matches OU, Over.Under, and mixed forms like Over.U or O.Under.

• Word boundaries \b at the start and end of the pattern prevent matches against substrings within larger words. For example, HOURS contains OU but has no word boundary between O and the preceding H or between U and the following R, so it does not match. Similarly HOUSE contains HOU but the trailing SE prevents a word boundary after U.

• Separators between components use .? (any single optional character) except between S(ide) and B(y) in the Side-by-Side pattern, which uses [\W_]? (non-word character or underscore). This is because .? would allow an alphabetic character in that position, causing false matches where a letter between S and B forms an unintended word. For example, SOBS would match as S[O]B[]S with .? consuming the O. Using [\W_]? restricts that position to only non-alphanumeric separators like dots, hyphens, spaces and underscores.

• Note that because the prefix is fully optional, double separators like H..OU or Half..SBS will still match. The prefixed path fails because .? only allows one separator character, but the engine falls back to matching bare OU or SBS at the end of the string where valid word boundaries exist.

• A year lookbehind (?<=\b[12]\d{3}\b) ensures the pattern only matches after a four-digit year in the filename. This is needed because 3D appears in actual movie titles (e.g. "Step Up 3D", "Jaws 3D", "Amityville 3D") and should not be matched as a format tag when it comes before the year. The lookbehind applies to the entire pattern rather than just the 3D branch to keep the regex simpler. In practice this has no effect on stereoscopic tags like SBS or OU since they do not appear in movie titles.