Multichannel audio tracks contain an individual channel for each signal in the track (for example, a 5.1 track would have six channels for left, center, right, left surround, right surround, and LFE).
5.1 format audio files and tracks conform to the Film track layout standard. Regardless of path assignments in the I/O Setup dialog, all 5.1 format audio tracks and meters follow the Film standard track layout:
Multichannel audio tracks are not required to mix in multichannel formats. Mono, stereo, and all supported track formats can be mixed using Pro Tools track outputs and sends (see
Multichannel Signal Routing).