Having issues with LtRt downmix
 

I'm currently downmixing a documentary from 5.1 to LtRt using Neyrinck SoundCode with the PL2 Encoder. (I haven't done this encoding myself before)

The downmix sounds good but I'm not so happy with the decoded 5.1 version.

When decoded, pretty much all the channels are all smeared together a bit. Music is bleeding into the centre from the L and R. Dialog and Narration are bleeding into the LR a bit, and it sounds phasey.

I don't know if this is pretty standard for decoded LtRt or if I'm messing something up.

If not, are there some ways to improve the decoded outcome?

Re: Having issues with LtRt downmix
 

Matrixed surround is always a compromise, and you will never get an Lt/Rt downmix to sound as good as the original 5.1 discrete mix when run through anything, and with DPL II your settings are critical to standing a chance.
Can you please tell me what your DPL II settings are?

Re: Having issues with LtRt downmix
 

LtRt should be retired IMHO.
It was a technology for a time when bandwidth wasn't available/ allotted for discreet surround channels.
Not only is the decoded signal often unsatisfying in surround, but it also to my ears makes the encoded stereo version lack definition.
It was great and clever for its time.

I don't see it being asked for so much on deliverables any more thankfully.
I hope it will gradually disappear.

Re: Having issues with LtRt downmix
 

Ok, thanks for clarifying that. I've since turned down the LSRS in Neyrinck which seems to be helping, The current settings I'm using are:

LR=0 C=-3 LSRS=-6 LFE=-3

Re: Having issues with LtRt downmix
 

No one is asking for LTRT anymore.
Im down mixing LoRo for the 2 channel mix.

Re: Having issues with LtRt downmix
 

Just starting a series for Disney Channel. The abc cable networks spec they sent me still has a LtRt as the 2 channel mix needed along with the 5.1. I queried it but they said it’s required.
Thinking of using the Atmos production suite to make them but there’s no way of listening back to check it.



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Re: Having issues with LtRt downmix
 

The thing to always bear in mind is that this will always be a compromise. Whilst there is an amount of wishful thinking that it is no longer required, this is not yet the case. Although it is indeed true that the 5.1 specs for HDTV are Dolby Digital, which is discrete (as far as it goes, anyway) plus has it's own downmix metadata it is still a good idea to know how to do this "old school" as only last year I was asked to supply a 5.1 & an LtRt - on DTRS of all things!!

Your settings are very similar to the default setup in a Dolby Digital encoder so should be an acceptable starting point but the only way to know you have it right for your mix is to constantly check, check, check. It's a double compromise too as you first have to compromise your 5.1 mix to a Matrixed Lt/Rt stream & check the decoded version in 5.1 (and this is hard enough) but you also have to compromise your stereo - and for me this was always the biggest problem as it is a serious compromise and a dedicated stereo mix will always sound better (at least to my ears it does).

I can highly recommend the RPGA Surround document as a good start point.

Re: Having issues with LtRt downmix
 

I was about to write more or less exactly the same thing.

Re: Having issues with LtRt downmix
 

The last 2 films I did they only asked for stereo so I gave them LoRo because it sounds better. So if you're seeing the same thing we can only hope it will spread out elsewhere?


LoRo usually sounds pretty good decoded to 5.1 anyway.

Re: Having issues with LtRt downmix
 

A LoRo will only upmix into faux surround - it will not decode because there is nothing to decode.