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A strange problem with LtRt
Old 16th December 2010
  #1
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danijel's Avatar
A strange problem with LtRt

I just had a call from the producer who attended a festival screening today - he reported a strange problem with our LtRt sound, which was already experienced twice in different festivals before, thus making this fatal enough for me to post the problem here.
It seems that on _some_ systems, center is reproduced very low - ie - voices sound 'roomy', music is louder in relation to dialog to the point that the dialog is unintelligible at places, while the music is ripping the ears off (note: we never have dialog and music at the same time). That is, at least, what the producer and the director have experienced, I haven't been to any of the problematic screenings myself. One of the theaters in question played the LtRt from the optical track on 35mm, while the other two played from HDCAM. We are assuming that the other films played normal in the same rooms (we were told so), but I can't confirm that. This same LtRt decoded perfect on one of the screenings that I've been to (while it played _mono_ at two other screenings I attended, even if the Dolby processors were set to de-matrix, but that's another story!)
My first impulse was to accuse the room of having a broken center channel, but now that it's happened for the third time, I'm really confused, and I'm starting to believe there's something I don't know.... They've spoken to the projectionist today, and he said that he noticed the problem and checked everything, and it's not up to them, but something's wrong with the copy.....
My only theory right now is that L and R channels were somehow misaligned by a couple of 10ths of milliseconds while being copied to the tape, so that the decoder has gone mad, but in that case, I'd expect the center information to go to the surrounds, not disappear alltogether.....
I know it's a long shot, but does anyone have some other crazy theory?
Old 16th December 2010
  #2
Quote:
Originally Posted by danijel View Post
My only theory right now is that L and R channels were somehow misaligned by a couple of 10ths of milliseconds while being copied to the tape
No way! I know there are panned dialogues in your film - was there a difference when these travelled from channel to channel? Not to mention that I heard your film in an average theatre in Estoril, played back from a HDCam tape, and it sounded very balanced.

OTOH, you'd be surprised finding out how many misaligned replay systems exist out there...

Try to arrange another screening in that room (btw, which one was that?) to hear the problem yourself, it's really difficult to guess without even hearing it!
Old 16th December 2010
  #3
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Quote:
Originally Posted by danijel View Post
I just had a call from the producer who attended a festival screening today - he reported a strange problem with our LtRt sound, which was already experienced twice in different festivals before, thus making this fatal enough for me to post the problem here.
It seems that on _some_ systems, center is reproduced very low - ie - voices sound 'roomy', music is louder in relation to dialog to the point that the dialog is unintelligible at places, while the music is ripping the ears off (note: we never have dialog and music at the same time). That is, at least, what the producer and the director have experienced, I haven't been to any of the problematic screenings myself. One of the theaters in question played the LtRt from the optical track on 35mm, while the other two played from HDCAM. We are assuming that the other films played normal in the same rooms (we were told so), but I can't confirm that. This same LtRt decoded perfect on one of the screenings that I've been to (while it played _mono_ at two other screenings I attended, even if the Dolby processors were set to de-matrix, but that's another story!)
My first impulse was to accuse the room of having a broken center channel, but now that it's happened for the third time, I'm really confused, and I'm starting to believe there's something I don't know.... They've spoken to the projectionist today, and he said that he noticed the problem and checked everything, and it's not up to them, but something's wrong with the copy.....
My only theory right now is that L and R channels were somehow misaligned by a couple of 10ths of milliseconds while being copied to the tape, so that the decoder has gone mad, but in that case, I'd expect the center information to go to the surrounds, not disappear alltogether.....
I know it's a long shot, but does anyone have some other crazy theory?
Was your LtRt mix file delivered as a 2 tr poly or two discrete tracks? How did the files get copied onto the HDCAM, ie how did the playout work? What sort of deliverables were given to the people who made the soundtrack neg? What happens to that mix when it is played as straight stereo w/ no Dolby decode? How about in MONO?

phil p
Old 16th December 2010
  #4
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danijel's Avatar
Thanks guys, I guess my post was more a desperate howl, because as Philip points out, there are obviously missing info - ie, I never checked the tape itself, nor did anyone else listen to it through a decoder - as always, we did everything at the last minute (BTW, I delivered split stereo to the video house; mono and stereo also play back great - that's why I've told them to ask the festival to play it in mono tonight, at the second screening.)
Branko, that is a good piece of information - hopefully, the tape in question will be the same one that played back in Estoril, so it will still be down to those playback systems. I'll PM you the names of the places, so as to not to make a big deal about it
Old 16th December 2010
  #5
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If this was a copy of what you did, it could possibly be that they flopped the L/R phase in the transfer. That would play hell with Lt/Rt.
Old 16th December 2010
  #6
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Quote:
Originally Posted by Rick Sanchez View Post
If this was a copy of what you did, it could possibly be that they flopped the L/R phase in the transfer. That would play hell with Lt/Rt.
If they flopped the phase of one channel, then the dialogue would be coming out of the surrounds. It sounds like an alignment/level issue really.

Randall
Old 16th December 2010
  #7
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If the fest plays it in mono and the dub has a misalignment between the chan then the results could be very ugly. They need to get that tape or print to another venue and try it there... Instead of summing the stereo to mono for a desperation screening, it would be safer to have mono by playing only ONE of your channels to the LCR speakers only....since there seems to be an unpleasant interaction between the channels.

phil p
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