Thanks, I always forget the Dolby Pro Logic matrix parameters. This document refreshed my understanding and if I read it correctly the Dolby Pro Logic does not support stereo surround speakers but a mono signal to both surround speakers. This means that Dolby Pro Logic is 4.1 max and IIRC the .1 lfe is not a discrete signal but a low frequency signal derived from the full signal. Does that sound about right?
--- In Avid-L2@yahoogroups.com, Andi Meek <kwikpasta@...> wrote:
>
>
> Hi John,
>
> Sorry to be a bit late to the party but I stumbled upon this description of Lo/Ro and Lt/Rt from the BBC and it reminded me of this thread. It's got quite a nice visual description of where the seperate tracks from the 5.1 mix go to when folded down. It's on page 21. It's also quite an interesting document on Dolby E generally.
>
> http://downloads.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP175.pdf
>
> Cheers,
>
> Andi
>
> To: Avid-L2@yahoogroups.com
> From: bigfish@...
> Date: Tue, 25 Oct 2011 21:22:27 +0000
> Subject: [Avid-L2] Re: Lt,Rt vs. Lo,Ro vs. Stereo L&R
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> I did label it as Stereo but they want either Lt,Rt or Lo,Ro. I've been told that because there is not dolby phase matrixing for the older dolby pro logic Lo,Ro is correct as in Left only and Right only. I still watch TV at home with my dolby pro logic receiver and it still works on prime time episodics and others so I believe it is still in use. I do agree stereo left and right is accurate but they want Lo,Ro and that's what they are going to get. If you ask me it's much to do about nothing but then they receive many different audio configurations depending on the requirements of a particular show and at least this way it will be consistent with the others and their cataloging of assests.
>
>
>
> --- In Avid-L2@yahoogroups.com, Dennis Degan <DennyD1@> wrote:
>
> >
>
> >
>
> > On Oct 24, 2011, at 4:05 PM, John Moore wrote:
>
> >
>
> > > In delivering a 2.0 mix that is not dolby pro logic a network wants
>
> > the channel assignment to reflect Lt,Rt or LoRo. Since we are not
>
> > doing any dolby matrixing on the mix the channels are really just
>
> > stereo left and right. I will therefore slate them as Lo,Ro. It just
>
> > seems to me that the Lo,Ro is for a downmix or fold down which we
>
> > haven't really done and seems inaccurate to label them Lo,Ro. Is
>
> > there any difference in Lo,Ro and stereo left,right?
>
> >
>
> > I say:
>
> >
>
> > I've never heard of "LoRo" before. If you're sending them a stereo
>
> > mix derived from a 5.1 mix, it should be labeled "LtRt" (assuming that
>
> > the mixdown contains all the tracks; front, center, rear surround and
>
> > LFE). The fact that it's not matrixed for Pro Logic shouldn't be an
>
> > issue.
>
> >
>
> > John also said:
>
> >
>
> > > Lt/Rt is a downmix suitable for decoding with a Dolby Pro Logic
>
> > upmixer to obtain 5.1 channels again. Lt/Rt is also suitable for
>
> > stereophonic sound playback on a hi-fi or on headphones as it is.
>
> > Lt = L + -3dB*C + -3dB*(-Ls -Rs)
>
> > Rt = R + -3dB*C + -3dB*(Ls + Rs)
>
> > (where Ls and Rs are phase shifted 90°)
>
> > [edit] Left only/Right only (Lo/Ro)
>
> > Lo/Ro is a downmix suitable when mono compatibility is required. Lo/Ro
>
> > destroys front/rear channel separation information and thus a Dolby
>
> > Pro Logic upmixer will not be able to properly extract 5.1 channels
>
> > again.
>
> >
>
> > I offer:
>
> >
>
> > Even though your above specifications appear to be accurate, I
>
> > wouldn't be so literal about it. Nobody uses Pro Logic anymore.
>
> > Further, Dolby Pro Logic (and its successor, Pro Logic II) do not
>
> > extract 5.1 channels from LtRt. Pro Logic only extracts L,R,C, and S;
>
> > only one surround channel and no separate LFE channel. You can never
>
> > get 5.1 from an LtRt Pro Logic mix.
>
> > Why not just label it as it is: "STEREO"? It's an accurate
>
> > description of the audio. Surely they have STEREO in the specs.
>
> >
>
> > Dennis Degan, Video Editor-Consultant-Knowledge Bank
>
> > NBC Today Show, New York
>
> >
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
No comments:
Post a Comment