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Old 05-05-2006, 12:59 PM
SFXPost SFXPost is offline
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Default Dolby Surround Tools encoding wrong?

I'm hoping you all can help us! We noticed recently that if we send audio to hard front left and hard front right, it gets DEcoded in the left, right, AND center or just in the center!? Even when it's two completely separate audio files (not just a mono file with center % 0 - although when doing that, the ENcoder says that it's in only the left and right channels, but when DEcoded it's in full center!)

We thought our routing had gotten screwed up, but we opened the Dolby template, it does the same thing with their busing as well! We're assuming that it's an ENcoding problem because we use the Dolby Surround DEcoder in one room, but in the other room we have a hardware SDU-4 and it's decoding it the same way.

Shouldn't the ENcoder and the DEcoder be showing the same thing?

I'm hoping someone can help please. Please let me know if I need to provide any more information to help you all solve this!

OSX 10.4.5
PT 7.1 cs6
Dolby Surround Tools 7.0

Holley
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Old 05-05-2006, 01:07 PM
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Default Re: Dolby Surround Tools encoding wrong?

is the L & R de-correlated?
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Old 05-05-2006, 01:12 PM
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Default Re: Dolby Surround Tools encoding wrong?

I'm not sure I know what you mean? If it's two completely seperate audio files, for example, tone on the left and dialogue on the right, then it will be DEcoded in the left, right, AND center. If it's just two channels of tone, one panned hard left, one panned hard right, then it gets DEcoded in only the center channel. (Even though in both cases, the ENcoder shows nothing going to the center channel)

If you mute one of the sides in both examples, then it gets DEcoded correctly in only the left or right, but when both are playing it doesn't match the encoder.
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Old 05-05-2006, 01:26 PM
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Default Re: Dolby Surround Tools encoding wrong?

i think you do get what i mean. two channels of tone are correlated.

are you doing 5.1 to LCRS?

and what is going 6-->4 (Enc) is correct, but the 2 (ltRt) DEcode is incorrect? is that what you are saying?

if it is a steering issue, then try some minimal EQ to one side to alter is phase slightly.

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Old 05-05-2006, 01:43 PM
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Default Re: Dolby Surround Tools encoding wrong?

We are not going from 5.1 to LCRS, we're just doing LCRS from the beginning.

I don't think it's a phase issue because even when putting tone on one side and dialogue on the other, it's still putting audio into the center channel. So even when there are two different audio files on each side, and the ENcoder is showing that there's nothing being sent to the center, the DEcoder is showing level coming out of all three. (left, right, and center)

Question: What about a mono channel? What is the point of the center% if even when you set it to 0 and the ENcoder is sending it to just the right and left channel, if the DEcoder puts it right back into the center?
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Old 05-05-2006, 01:48 PM
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Default Re: Dolby Surround Tools encoding wrong?

The Encoder and Decoder won't always show the same thing in this case - this is due to common information between your left and right channels.

Let me explain. no there is too much, let me sum up...

the decoder (kind of) works as follows:
All in phase common (ie, mono) information shared between the L/R of your post encoded file will decode in the center (ie, your tones)

All in phase stereo information will go the the L/R of your decode

All out of phase information will decode to the surround.

I understand that this is an opver-simplification of this, however...

As shown when you sent your in phase tones to both the left and right. Since there are in phase and mono to each other they will be decoded as mono. Something similar will happen when you encode and decode BGs(for example) that have a fairly narrow stereo spread. Even though they are panned hard right/left in your 5.1 or LCRS, since they share a large amount of in phase/mono information it will decode with some information to the L/R but with more information into the center. You will also see this with stereo music, which naturally has some mono information, and lots of in/out of phase information. Even though you might mix it to only be hard left/right after the encode/decode process it will decode in all four speakers (LCRS)

Hope this helps more than it confuses..

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Old 05-05-2006, 02:08 PM
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Default Re: Dolby Surround Tools encoding wrong?

Okay, that makes sense,

So then what is the point of the center % option?
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Old 05-05-2006, 03:38 PM
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Default Re: Dolby Surround Tools encoding wrong?

Quote:
So then what is the point of the center % option?
you mean in the panner window?

well, if mixing 5.1, you may chose to just send a sound to the L & R with a phantom center to make room for the dialogue which is in the Center, so, 0%. headroom.

but you know the problem of a phantom center in a theater? people sitting on the Left will hear it as coming from the Left. with the Center channel, your sound is anchored there and audience members sitting on the left hear the sound as coming from the center.
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Old 05-09-2006, 12:19 PM
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Default Re: Dolby Surround Tools encoding wrong?

Yes, exactly, I guess the flaw in my thinking was that the phantom center would also occur in ProLogic.

Thanks

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