Georgia Hilton MPE CAS MPSE Prod/Dir/Editor

Film Services Professional ( Producing / Editing / Delivery )

Blog

Stereo downmixes (or fold-downs)

Posted on February 28, 2010 at 1:00 AM

Stereo downmixes (or fold-downs)

Left total/Right total (Lt/Rt)

Lt/Rt is a downmix suitable for decoding with a Dolby

Lt = L + -3dBC - -3dB(Ls + Rs)

Rt = R + -3dBC + -3dB(Ls + Rs)

(Ls,Rs 90-degree phase shifted)

Left only/Right only (Lo/Ro)

Lo/Ro is a downmix suitable for stereo playback

Lo = L + -3dBC + attLs

Ro = R + -3dBC + attRs

(att=-3dB or -6dB or -9dB or 0)

5.1 downmix

5.1 to LR Ls to L drop 6 db (.5) , Rs to R drop 6 db (.5), C to L & R drop 3db (.707) , lose the sub.

or

Lt = FL + s*SL + c*C

Rt = FR + s*SR + c*C

where s (=surround mix) is usually something between 0.5 and 1

and c (=center mix) is usually 0.7. This would be a "normal" stereo downmix.

or

Lt = FL + s*(SL+SR) + c*C

Rt = FR - s*(SL+SR) + c*C // 180° phase shift SL+SR

with s=0.5 and c=0.7.

cheers

geo __________________

ms georgia hilton mpse cas


Categories: None