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Decoding a Height Channel

Discussion in 'AV Receivers & Amplifiers' started by Stuart M. Robinson, Mar 2, 2003.

  1. Stuart M. Robinson

    Stuart M. Robinson

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    It might be worthwhile clearing up some confusion over the availability of an encoded height channel on a couple of DVDs, specifically ‘We Were Soldiers’ (2002, Paramount), now that TAG have produced a product with a specifically designed “height channel”.

    Currently, there are no DVDs with a height channel, ‘We Were Soldiers’ included.

    Roger Dressler (Dolby):

    “On the ‘We Were Soldiers’ DVD, the encoding used for the height channel was, err, nothing. There is no height channel on this DVD, as it was not made from the soundtrack version produced after initial release and used in a couple of theaters with height speakers.”

    There is also an interesting AVS thread on the subject, in which the movie’s sound re-recording mixer comments upon the soundtrack:

    Marc Fishman (Sound Re-recording Mixer):

    “I was the dialog and music re-recording mixer on ‘We Were Soldiers’. I was involved in the overhead mix from the planning stages. Our first idea was to release the film theatrically with the overhead mix in the DTS format, since they could carry the surround information discretely. When we first mixed the film, we mixed in the Dolby EX extended surround format. For the overhead mix, new sound elements were added and some of the existing mix was folded into the center channel. Dolby heard about the idea and contacted us with their idea. The Dolby EX encoder/decoder process is a modified matrix process. It differs from the normal matrix in that it knows that if there is mono information sent to both surrounds, they will remain ‘on the wall’ and will not bunch up to the rear surround. Dolby further modified this process, so the surround array becomes a 2 channel encoded Lt/Rt, as it is in the EX version, but instead of LS/CS/RS only, we also derive the OH from where the surround info would normally live on the Lt/Rt....

    “Regarding the DVD: It is my understanding that the DVD used the 24bit Dolby EX encoded master that was used for the theatrical release. We didn’t do the Overhead mix until July, and there was no new print master struck for reels 1 and 7 since we added no new material to those reels.... so while there was a limited release in Arizona of the overhead mix, I believe that outside of that, no one else has heard that mix.

    In a later follow-up message, Marc confirmed:

    “We never turned over materials for video mastering that were encoded with anything other than the Dolby Digital EX printmaster for ‘We Were Soldiers’. When we made the Overhead version, all we created was a new overhead channel which was mixed into the existing 6.1 channel discrete printmaster. We never made a new encoded printmaster.... we handed over the elements to Dolby and they did all of the OH encoding in house for the theatrical re-release....”

    So, in short, any content in TAG’s (or Circle’s) height channel is currently ‘accidental’ (similar to applying Dolby Pro Logic to non-encoded material) and not by design, even with the ‘We Were Soldiers’ disc. Just like matrix EX, sometimes the results may be desirable while at others far from ideal. Your mileage may vary, as they say.

    Stuart M. Robinson
    SMR Group – http://www.smr-group.co.uk/

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