Premiere Pro provides a method for synchronizing audio and video called Merge Clips. This will streamline the process by which users can sync audio and video which have been recorded separately (a process sometimes called double-system recording). You’ll be able to select a video clip and synchronize it with up to 16 channels of audio by using the “Merge Clips” command. Clips which make up the merged clip are referred to as “component clips.”
Clips may be merged by group selecting them in the either the Project panel or the Timeline. The Merge Clips command may be invoked via either the Clip menu or a contextual menu. It is a contextual command, so more than one clip must be selected in order to enable it.
You may merge one or multiple audio clips to a single video or AV clip. The total number of audio tracks permissable in a merged clip is 16, including any combination of mono, stereo or surround 5.1 clips. A single mono clip counts as one track, a single stereo counts as two tracks, a 5.1 clip counts as six tracks.