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  #11  
Old 12-03-2019, 04:38 AM
Cheesehead Cheesehead is offline
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Default Re: Having issues with LtRt downmix

You're right of course, it upmixes rather than decodes, but it still sounds ok.
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  #12  
Old 12-03-2019, 10:58 AM
Leverson Leverson is offline
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Default Re: Having issues with LtRt downmix

Adding my voice to the chorus that hates LtRt's. They were ingenious during a time when 6-channel mixes had to be stored on 2-channels of analog tape, but they really do compromise the sound. I much rather prefer the sound of a discrete 5.1 mix and a 2.0 LoRo mix.

I'm also happy to see them slowly be phased out (excuse the pun) of most specs.

But if you are still in a position where the spec sheet demands an LtRt, I generally use Minnetonka SurCode, although I'm sure Neyrinck SoundCode works just as well.

However in any case you will need to monitor the decoded signal (original 5.1 ---> Encoded Stereo ---> Decoded surround) and make adjustments in your mix to help correct steering issues. You will always have some bleed between all the channels, it's the nature of the beast, but often with aggressive music or panned sound effects you might get weird steering 'pulls' where a sound jumps to the fronts or surrounds in a way that doesn't sound good.

Be especially careful with any kind of music that uses any kind of phase trickery like stereo wideners. I hate those things. They, and anything else that plays with phase, will wreak havoc on your LtRt, since it's a phase-encoded medium. The only solution I've found is to narrow the music down so it isn't as wide, until it stops pulling funky. (So if any composers are reading this please don't use any sort of artificial widener or phase trickery on your score tracks).

It's a bummer to have to reduce width or make pans less aggressive and generally make your surround mix more mono, but that is life with LtRt's. I can't wait for a future where they are dead technology and gone from every spec sheet.
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  #13  
Old 12-03-2019, 01:10 PM
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spoons spoons is offline
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Default Re: Having issues with LtRt downmix

Genuine question. Who’s actually listening to the LtRt decoded ?
I assume the HD broadcast uses my 5.1 discrete mix and a stereo mixdown for anyone listening in stereo.
Am I right in saying my LtRt will only be listened to decoded by someone who has a pro-logic system and is listening to the SD broadcast ?


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  #14  
Old 12-04-2019, 01:07 AM
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neilwilkes neilwilkes is offline
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Default Re: Having issues with LtRt downmix

Quote:
Originally Posted by spoons View Post
Genuine question. Who’s actually listening to the LtRt decoded ?
I assume the HD broadcast uses my 5.1 discrete mix and a stereo mixdown for anyone listening in stereo.
Am I right in saying my LtRt will only be listened to decoded by someone who has a pro-logic system and is listening to the SD broadcast ?
Sadly more common than you might think.
With TV the "standard" for HDTV is AC3 but again if the system is set up to defaults it will be stereo, meaning LtRt at best as things like the Sky HD Q box are never set to Dolby Digital by default, but stereo only as most people hook up the TV box straight to the TV via an HDMI line which out of the box is always, always set to stereo (the idea supposedly being setups are defaulted to get sound & picture up for as wide a range of hardware options as possible in order to allow the user to set it up properly from there).
Unless things have been set up by the end user to discrete 5.1, it will be an upmix or an LtRt, depending on the source.

It's even more complicated with optical discs - I still have in my emails a support request we got asking why the user was not getting the 5.1 output promised on the disc. A few questions asked revealed he did have a 5.1 setup - sort of (Sub/Satellite system) but it was actually connected up with RCA type connectors - Red & White. In short, he had a stereo output connected to a sub satellite system and genuinely did not understand why this would not work. I kept the email as a reminder of what can go wrong, even when a customer pays the store for installation.

Regarding monitoring, I am not familiar with Neyrinck as they seem to only cater for Mac OS (I run a PC) but they seem to know what they are doing and are properly licensed too. For DPL II and other Dolby Matrix systems I use the Minnetonka Audio DPL II encoder/decoder plugin (as well as the standalone one) and usually render out the export in real time, tracking this straight back in to the project for comparative tests in both stereo & surround modes.
Matrix surround always has been and still is a compromise - there is simply no getting away from this. That said, AC3 also downmixes automatically so be careful with the metadata there or you can ruin your mix ever so easily - dialnorm must be set correctly for the content, and adding "production information" metadata can also bring the hammer down on your mixes as well. DTS-HD Master Audio also has the option to embed an LtRt in the stream, and this should always be used if only because someone playing a 5.1 mix - or trying to - on a stereo only system may well get just front left/right and nothing else even if a separate dedicated stereo mix has been supplied and if 2 streams are included, default to the stereo one on optical discs - just in case.
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