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vanilla stereo versus dolby prologic II

ssj

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was wondering if someone more knowledg. . . knowlejubble. . . fuck it, smarter than i could weigh in, please.

i'm editing a movie with a mono soundtrack and adding a stereo score. i don't know whether this matters, but the project in my NLE is in 5.1, but only the center channel has original audio.

the core questions: in my final encoding, should i output to stereo or dolby prologic 2? is there an advantage of one over the other?

and for stereo audio, will 5.1 audio systems automatically convert the stereo signal to one that utilizes all sound channels, or does the sound remain limited to only two of the available speakers?

senkyu in ardvaance.
 

Captain Khajiit

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If you want 2.0 output (as I believe you should in this instance), I don't understand why you say that the project in your NLE is 5.1.  Set it to stereo.

ssj said:
and for stereo audio, will 5.1 audio systems automatically convert the stereo signal to one that utilizes all sound channels, or does the sound remain limited to only two of the available speakers?

It depends on the format of the 2.0 audio.  When you encode 2.0 to AC-3, you have option of setting a flag to signal whether the stream is pure stereo or DPL.  If you flag the track as surround encoded, the A/V receiver should pick up this flag and upmix the audio automatically.  PCM has no such flag, so the user normally has to select upmixing manually.  This addresses your core questions too, I believe.

Why don't you use the 3.0 audio that you mentioned in your thread?  Obviously, the studio took the mono mix and manipulated it to produce directionality, so it's not real 3.0, but the result will almost certainly be better than a fan-made attempt and should integrate with a stereo score far more smoothly than the mono.
 

ssj

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thanks, cap K.

long story short: i thought i had 3.0 audio, which meant utilizing three of the surround channels during editing. later i learned there was some unspecified issue in FCP X, so i was reduced to true mono for the film audio.

by then, i'd already made countless changes to the audio, so swapping from mono to 3.0 was something I didn't want to fathom.

so the verdict is plain ol' stereo, si? senkyu, feline captain.
 

Captain Khajiit

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so the verdict is plain ol' stereo, si?

I don't understand what the unspecified issue in FCP was, so it's hard for me to envisage what you're dealing with.  If you ended up using the mono track from the disc, then your project is going to have dual mono with sections from your score that are true stereo (unless. of course, you downmix those to mono as well.)  While I understand that you don't want to re-do extensive work, I don't see how you're going to implement a solution without some changes to your workflow.

If I were embarking on a project like yours, I should downmix the 3.0 to 2.0 (pure stereo)  and integrate it with the stereo score.  An alternative solution would be to downmix the stereo score to mono in order to integrate it with the film's mono track, ensure that both are dual mono, and then set up a stereo project  (unless FCP happens to have a dual-mono option).
 

ssj

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I truly have no idea what FCP did. I thought I imported 3.0 audio, but since it gave me mono, I'll make my lemonade with it—it works well enough. Before export/downmixing, I've got film mono in the center track, and Star Wars stereo audio in the left and right channels.

I appreciate your advice, cap K. lessons for next time—turn 3.0 into stereo, edit from there.
 

ssj

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Thanks, man!

Losing 2/3 of the 3.0 audio is only slightly disappointing. Since those two thirds don't contain any discrete information unavailable in the original mono, it's not that much of a loss.

It's as if I edited the original mono track from the start. At least that's the perspective I want to maintain.
 

Captain Khajiit

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That's true.  You might want to look at the options in FCP to see if there's one that converts 1.0 to dual mono.  There ought to be, and it should help.  In Vegas, it's a matter of right-clicking on the audio track, selecting the track that does contain audio, and choosing to use only that one; thereafter, one should have dual mono.

EDIT:  For future reference, here's how to downmix 3.0 to true stereo.

Code:
function Dmix3Stereo(clip a) { # 3 Channels L,R,C or L,R,S
 flr = GetChannel(a, 1, 2)
 fcc = GetChannel(a, 3, 3)
 return MixAudio(flr, fcc, 0.5858, 0.4142)
}
 

Neglify

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ThrowgnCpr said:
chocolate stereo or GTFO

025c1691-5863-4969-811b-03f1482126ab.jpg
 
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