Originally Posted by scottd327
What is the big need for PCM 7.1 capability? There are no movies mixed in 7.1.
Folks want to be prepared in case 7.1 mixes do show up. Is that so unreasonable?
Even if they eventually remix some older soundtracks in 7.1, how different would it be from applying PLIIx to 5.1 LPCM, which you can do now to derive 8-channel playback?
Probably not too different, though discrete channels always have the potential to sound better than matrix derived channels.
If you are already receiving 7.1 of uncompressed channels, what would Logic 7 do for that?
Aside from converting 2-channel and 5.1-channel material to 7 output channels (like PLIIx
does), LOGIC7 also steers the contents of discrete soundtracks based on where those sounds image (which PLIIx
doesn't do). This could be adapted for discrete 7.1 soundtracks.
For example: suppose you're listening to concert hi-def disc with a discrete 7.1-channel soundtrack, and suppose the recording engineer mixed the lead vocals in the front L/R channels instead of the centre (not uncommon with multi-channel music mixes). The vocals will image at the correct location (middle of the front soundstage) only for a listener in the sweet spot.
LOGIC7 will extract common mono information (like lead vocals) from the front L/R channels and steer it to the centre channel, where it is combined with the information in the existing discrete centre channel, before being sent to the centre speaker. Basically anything that would normally image at the centre of the soundstage, whether it is in the centre channel or in the front L/R channels, will end up being played back by the centre speaker. This way, no matter where you're sitting, those sounds always image at the correct/intended location. No collapsing to the nearest speaker.
The same thing is done with decorrelated (out of phase) sounds, which normally image outside the front soundstage. Those sounds are extracted from the L/R channels and steered to the surrounds, where they are combined with already existing discrete surround information, and output from the surround speakers.
So even with discrete 7.1 content, L7 could still do logic steering to place sounds where they would have phantom imaged. I say "could" because the L7 algorithm is currently designed for 5.1/6.1 discrete multi-channel sources. Like I said earlier, it would need to be updated for discrete 7.1-channel sources. But the same principles would apply.