From Rolling Stone article:
Page first announced the reissues in November 2012. Each album will come out as a deluxe edition that he told Rolling Stone would include "added sonic and visual thrills." Page explained that he intended the reissues to include alternate mixes of the band's songs, as well as concert recordings that were never officially released. He also said that the albums will sound much better than the versions now available. "The catalog was last remastered 20 years ago," he said. "That's a long time. Everything is being transferred from analog to a higher-resolution digital format. That's one of the problems with the Zeppelin stuff. It sounds ridiculous on MP3. You can't hear what's there properly."
