Here is a second video laying groundwork for a discussion of style.
Another example of stylistic shift over time affecting pronunciation and thus meter.
Of particular interest here, is the letter "thorn", a strange letter that looks like a lowercase "b" mashed with a "P" (check the video for an example). This letter did not survive the onset of printing, as, much as English printers tended to replace German umlauts with uncontracted vowels "ae", "oe", and "ue", Continental printers replaced the thorn with y. So "thee" and "thou" turned into "ye" and "you" on the page, obscuring the last remnants of the informal "you" grammar inherited from Anglo-Saxon. (It wouldn't surprise me to learn that it sped up the elimination of the informal tense as thee and thou became ye and you, and eventually just you.)