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
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