Zhèbù diànyǐng de zhǔyǎn shì shéi, zǎoyǐ jìnrénjiēzhī.
Who stars in this film has long been common knowledge.
Tips
usage
Formal alternative to 人人皆知. Typically introduces a fact so obvious the speaker wants to dismiss argument about it. Compare 众所周知 (widely known) which is slightly more common in written style.
grammar
尽 here means 'all, every' - read jìn (not jǐn). Often functions as 定语 before a noun: 尽人皆知的秘密 'an open secret known to all.'