Is it possible to decode LoRo?

[pechnatunk]

Not that I want to...

I'm finally getting over the whole Dolby brain explosion.
The revelation came with realising LtRt s purpose is pretty much purely to carry surround channels through existing stereo plugs. (oversimplified?)

Does this mean it will soon be redundant now with optical and HDMI?

I think my following questions are about to answer no to that anyway.


I'm doing a final mix for a film which is about to be sent to a film festival.
The only info I have yet is -

'We have digital projecton, so the hard drive route is a good one. Please make sure yoursound is rendered, there is noothing worse than an irate audience who complain about sound. Bear in mind we have 7.1 dolby surround. As a back up maybe you should also enclose a DVD version.'

My film is plain old, flush of the toilet stereo. Is there a way to bottle it so that it does not get decoded as LtRt?

There's no way I'm embarking on an unwrapping mission.
I only have two speakers anyway.
And if it is possible - can I do it without a Dolby encoder? (I'm risking the very silly question since I'm 99% sure there will not be budget for Dolby)

If not, how much does it affect the mix?
If dialogue is slightly off centre, will it be lost?

I'm also curious for multi-channel and metadata, what file format is generally used if being played off a drive - is it still AC3, or is that only for DVD authoring?

Thanks - a lot of questions there..

[philper]

Originally Posted by pechnatunk

Not that I want to...

I'm finally getting over the whole Dolby brain explosion.
The revelation came with realising LtRt s purpose is pretty much purely to carry surround channels through existing stereo plugs. (oversimplified?)

Does this mean it will soon be redundant now with optical and HDMI?

I think my following questions are about to answer no to that anyway.


I'm doing a final mix for a film which is about to be sent to a film festival.
The only info I have yet is -

'We have digital projecton, so the hard drive route is a good one. Please make sure yoursound is rendered, there is noothing worse than an irate audience who complain about sound. Bear in mind we have 7.1 dolby surround. As a back up maybe you should also enclose a DVD version.'

My film is plain old, flush of the toilet stereo. Is there a way to bottle it so that it does not get decoded as LtRt?

There's no way I'm embarking on an unwrapping mission.
I only have two speakers anyway.
And if it is possible - can I do it without a Dolby encoder? (I'm risking the very silly question since I'm 99% sure there will not be budget for Dolby)

If not, how much does it affect the mix?
If dialogue is slightly off centre, will it be lost?

I'm also curious for multi-channel and metadata, what file format is generally used if being played off a drive - is it still AC3, or is that only for DVD authoring?

Thanks - a lot of questions there..

You can send your LoRo mix out to festivals and it will probably be ok. We usually make LtRts because A: I like having the music and ambs. "wrap" the audience a little when surround and decoding is available and B: it is hard to know if you will have "steering" issues w/ uncorrelated stereo sources in your mix until you hear what a decoder does to the mix. My recent experience w/ festivals is that you cannot count on them changing their playback settings between films, and most 2 channel mixes they will get WILL be LtRts, so it is very likely that your mix will be sent thru the decoder anyhow. BTW, there is no charge from Dolby for making an LtRt, you are thinking of Dolby Digital etc which requires a license and a printmaster made in a Dolby-approved room. The best you can do with your LoRo is to make sure that it sums to mono w/o any cancellation, and check your stereo on a phase meter (plug or whatever) to make sure you don't have any interchannel phase issues (often the source of these is pop music recordings).

phil p

[pechnatunk]

Originally Posted by philper

BTW, there is no charge from Dolby for making an LtRt,

Thanks for the info.
Sorry - too many thoughts made my main question a little convoluted.

I was reading about the metadata in Geo's sticky.

"Channel
Mode
Setting Definition and Data Rate 1+1 Dual mono (not valid for DTV broadcast or DVD production)
1/0 Mono From 56 kbps, usually 96 kbps
2/0 Stereo From 96 kbps, usually 192 kbps
3/0 From 256 kbps
2/1 From 256 kbps
3/1 From 320 kbps
2/2 From 320 kbps
3/2 From 384 kbps, often 448 kbps"


Is it possible to encode 2/0 info on to my LoRo to ensure it plays back accordingly even through the decoder? For Free?
And if so, where should I start?
I should be able to get access to Final Cut Studio or possibly other programs - if they do it.
Or am I misunderstanding Geo's info?

[eoats]

I very much agree with Phil.

One minor nit; I was advised by a Dolby tech that any exhibition for a paying audience does require a license. Very often Dolby charges little or nothing for their "Festical rate" & they don't strictly enforce this, the law is on their side.

It would be on the exhibitor & venue to own up to Dolby if they 'mistakenly' decode your LoRo. I listen to all my mixes nearly all LoRo, to check for compatibility with being decoded.

Dolby - Apply for a License

[eoats]

Sorry, I kinda went off there.

It would seem trying to 'force' a Left-right playback of a 2 channel mix in a 5.1 template is not destined to end well. My thoughts are of someone in a projection booth or in front or their reciever/home theater trying to find the 'missing' Center & surround tracks that is indicated in the metadata but can't be seen or heard.

a LoRo being decoded as an LtRt would be much less painful.

My $.02

[mikevarela]

Originally Posted by philper

most 2 channel mixes they will get WILL be LtRts, so it is very likely that your mix will be sent thru the decoder anyhow.
phil p

Just to clarify the question/answer - wondering myself

If the Stereo mix gets sent through the box, what type of issues will it exhibit on playback. I've also mixed stereo for people that said it was destined for festivals (not sure if it got there). In any case, being that he's mixing stereo, would any issues arise on playback that you can think of - un-intended issues I mean for the listener

[pechnatunk]

Thanks Phil, I'll check it sums to mono nicely.
What exactly should I be looking for in a phase scope?

Thanks eoats, you're right - I think I'll just be making things more complicated.
I'll have to just make sure it's very well labeled and hope for the best.

[ErikG]

Answer to "what happens on decode":
Anything that's mixed mono in-phase and equally strong in both channels Will ens up in the center.
Anything that contains in-phase mono signal but purposely sent to Left/Right will end up in Center.
A lot of signals with a weak/narrow stereo signal will sound collapsed as it mostly ends up in Center.

Stereo signals with positive phase will mostly stay L/R but the part of the sound that's in phase and does not contain a lot of "width" will end up in center.

Any discretely panned sounds that's sent to only L Or R will stay there.

Any stereo signal will also contain some out of phase signal as well. The more out of phase it is it will start to go to the surrounds. If it's 100% out of phase it will ONLY go to the surrounds.

To conclude: most natural stereo material will collapse to the center somewhat but the reverbs in stereo and wide ambiences and music will spread from left and right to the surrounds and "envelop" the listeners.

The worst problems seem to come from electrnically widened signals from synths and some cheaper reverbs and doubling delays that ind up in sync but out of phase with the main signal, these signals will end up in the surrounds and might sound pretty weird.


My suggestion would be to find someone close by that have multichannel monitoring and encode/decode equipment and listen to it so it won't sound to bad in the cinema. If you can go to a proper dub stage you could also check and correct the mix level.

[ErikG]

The last post was a bit messy...

Mono signals that are panned will stay as they where but panned l-c-r instead of l-r. They will not collapse.

So a mono panned car pass will work as intended. But a stereo car pass might actually start and end in the surrounds, it will depend on how it was recorded/processed/time aligned etc.

So in general a stereo mix done by someone who's used to mixing for tv or film will quite likely work pretty ok.
a mix done by someone who is a hobbyist or music mixer will quite likely have some less desireable issues.

[mikevarela]

Thanks Eric, that's what i was looking for.

Cheers

[vudoo]

From experience, festival set up varied anywhere from ok to absolutely horrid.

Due to the above factor, i've had way more problems with LtRt as oppose to LoRo. I ususually provide a 5.1 and LoRo and have not had any playback issues even with crappy set up.

[pechnatunk]

Originally Posted by ErikG

The last post was a bit messy...

Mono signals that are panned will stay as they where but panned l-c-r instead of l-r. They will not collapse.

So a mono panned car pass will work as intended. But a stereo car pass might actually start and end in the surrounds, it will depend on how it was recorded/processed/time aligned etc.

That's great to know - all my SFX, although panned, have mono source.
Atmos is Stereo - but that would be good in the surrounds.

I don't mind having reverbs in the surrounds either.
I''ll just have to double check that I mono-ise anything stereo where I used Speakerphone - guessing that has some phasing effects.

Just to be certain - It doesn't change levels of the left and right?

I read that in the encoding process the Centre material is reduced: -3 dB.
Does this mean in decoding, with LoRo, anything equal L and R will be boosted 3 db?