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Post #1074585

Author
yotsuya
Parent topic
Info Wanted: Is there 5.1 surround sound on the Despecialized Editions?
Link to post in topic
https://originaltrilogy.com/post/id/1074585/action/topic#1074585
Date created
9-May-2017, 12:28 PM

junh1024 said:

Anyways, I think using the Dolby Pro Logic IIx 6.1 decoder will yield better results even for mono surrounds than Dolby Pro Logic II 5.1 or Dolby Pro Logic 4.0.

Not necessarily. Decoders/upscalers decode to whatever output config you select.

The upscalers have NO KNOWLEDGE of the config of the source material, all they get is 2ch something. And they WILL upscale to any number of speakers you select.

DPL2x is 6.1 OR 7.1 (Again, whatever you select). DPL2x will (generally) NOT increase the discreteness of your upscale by a large amount, because there is only so much info you can store in (matrixed) 2ch (in fact, the most sortove discrete ch you can store in 2ch is 3ch with the best DPL2 decoding, you can only get more with extremely controlled synthetic conditions.). Using professional 5.1>7.1 upmixers, what’s in the back 4 is basically the same as the previous 2.

You can>: decode to 5.1 (DPL2) and mono the rears. OR decode to 4ch (DPL1) and stereoize the back.

That is not quite correct. The original Dolby Stereo (the 4 channel matrix encoding) contains 4 distinct channels. Sounds can be directed to any channel. Using Dolby Prologic II decoding may produce 5 channels, but the two surround channels are identical if the source only had 4 channels. When Dolby updated their encoding in the 80’s, they found a way to encode stereo surround channels. Dolby Prologic II decoding produces 5 distinct channels. Now there may be some crosstalk between channels that interferes with the purity of the mix, but anyone who did a matrixed mix should be paying attention to how it comes out of the decoder and there should be nothing significant. And the way Dolby decided to encode the LFE was to use the surround channels below 120 Hz. That gives you the full 5.1 channels from a 2 channel source.

Now when you apply this to Star Wars, the sources for the 77 and 85 mixes are not complete. True they are only missing a few frames, but to avoid any issue between 4 and 5 channels is to create a 4.1 or 5.1 mix where you can down convert the stereo surround of the 93 mix (the most complete) to the mono of the 77 mix. But you can never upconvert that mono surround to be anything else. You can apply a stereo field effect to it, but all that does is broaden the sound (I’ve played with this quite a bit to make a mono song not feel so out of place among stereo songs). You are limited by the source and the decoder. Whichever uses the fewest channels is what you get for output. It doesn’t matter how many surround speakers you have, the sound will be the same.