Film-Tech Forum ARCHIVE: Help with digital L&R for centre-channel reproduction.

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Posted by Rick Long (Member # 213) on 04-05-2003, 09:20 PM:

CP-500
Video projector with L & R outputs.

I have a show tommorrow using video with L and R channels. I understand there is a way to decode this for centre channel reproduction as well.

At the Toronto Film Festival, I saw Keith Madden do this by copying the 05 format, but was distracted before I got to see him finish the process. I beleive he used non-sync inputs for this.

Anyone got the programming I need to do this?

Thanks.

Posted by Daryl C. W. O'Shea (Member # 1303) on 04-05-2003, 09:31 PM:

Using the build custom format menu and selecting a copy of either 60 or 61 (non-sync 1 or 2) and unmuting the centre channel in that custom format should do what you want.

Alternatively using a copy of 05 and selecting non-sync 1 or non-sync 2 as the source would achieve similar results, in fact I'd try this way first.

Can't remember the key sequences from memory though, sorry.

edit: BTW, if the video source doesn't have a matrixed audio track it could sound pretty bad.

[ 04-05-2003, 10:38 PM: Message edited by: Daryl C. W. O'Shea ]

Posted by Michael Schaffer (Member # 1204) on 04-06-2003, 07:15 AM:

Menu > System Setup > Format Config > Build Custom Format > Copy From Existing Format.
Select a user format number that will not be confused with other already existing custom formats. Copy from Format 05.
Then go to NR source and select the N/S input. Go to NR type and select None since the audio on the video is most likely not SR-encoded. You can still test it with SR if you like and hear what it sounds like though.

Go to Optical Decoder Configuaration > Decoder mode and select ProLogic. This will enable the matrix decoding which unfolds the 2 channels to 4.
In this menu and in Equalizer config there are also buttons you can push to enable and config the subwoofer if you like. You could also build the format from an N/S format, but those are sometimes configured to send L and R to the surrounds and then you would have to reroute the channels. Which ís done in the X-Point menu.

Save the new format!
Sink on the carpet, face east and thank me.

Posted by Brad Miller (Member # 2) on 04-06-2003, 04:25 PM:

Easiest to start from non-sync and add pro logic matrix to it. You can leave the surrounds on or turn them off (same for sub), which just depends on your preference and how good/bad the mix is.

Do not use any form of NR...especially SR. It will sound bad.

Posted by Rick Long (Member # 213) on 04-06-2003, 11:56 PM:

Lets assume, for a moment, that a director arrives with his stereo (L R)print, in which he wishes us to use centre channel. A-type noise reduction is out of the question here.

As we have know for years, a person sitting equi-distant between two speakers, listening to a stereo recording, will hear a non-existant centre channel where there is in-phase information from both L and R channels. Is there a way to do this by-passing any noise reduction or is this an option in the set-up?

Gotta go vacuum my carpets. Thanks for the advice.

Posted by Michael Schaffer (Member # 1204) on 04-07-2003, 06:53 AM:

quote:
Is there a way to do this by-passing any noise reduction or is this an option in the set-up?

Rick, why do I sit down at the computer, put on my new glasses and type the procedure in step by step from the default screen when you don`t even read it? [Frown]

Some tapes come from the studio SR-encoded. Hopefully the director will know if it is or not, or there is info about it on the cassette, but in many cases the director unfortunately has no clue...

Once during the Berlin International Film Festival, we had a documentary on digi beta (SR-encoded, BTW). There is always a quick test run immediately before the show.
The dialogue was on the left channel, the athmosphere sounds on the right. The studio had sent the pre-mix tape. The director and producer got angry and said our sound systems were "broken". I had to have them and one of the official festival guys come up to the booth where I played the tape. I indicated the level readings on the player and switched off the two channels alternatively to demonstrate to them that it was like that on the tape. Then I told them we could set the CP500 to mono so we would have an instant mix. We also had a patch bay and mixer in the rack, so I offered them to sent the athmo to L and R, and the dialogue to C, and they were content.
I explained to the director and producer in detail what the problem was and how it was solved for this show.
There was a lot of nodding and aaaahhhh.

I knew that the docu would be played in another location the next day, so I put a note into the box explaining what the problem was and how it could be solved. Obviously that note got lost, because later I heard that they had test-run the tape and, of course, found the same problem. The producer freaked completely out before they had a chance to offer a solution and said the tape had worked at our location, so their sound systems must be "broken". Then he rushed off to complain to the festival office about the catastrophic technical problems of the festival locations...

Posted by Steve Kraus (Member # 476) on 04-07-2003, 07:28 AM:

Rick, just follow Michael's instructions to BUILD CUSTOM FORMAT copying from Format 5 but with the source set to one or the other Non Sync inputs and noise reduction turned off. Then go to the BUILD FORMAT SELECTOR to assign this custom format to a button.

Now do it all a second time with a different custom format number but this time go into Optical Decoder Config and set it to Lt / Rt Direct. Assign this format to a different button. You would use the first format for matrix playback. The second format is for a track not intended for playing through the matrix utilizing the phantom center as you mention. If music is bunching up in the center when using Pro Logic then it's a good bet that you want the left / right direct mode.

You may also try each of these with SR NR enabled.

Posted by Michael Schaffer (Member # 1204) on 04-07-2003, 07:45 AM:

quote:
Then go to the BUILD FORMAT SELECTOR to assign this custom format to a button.

Oh yes, I had forgotten that. What use is the most wondeful custum format when you can`t select it!
To distinguish between the center effect with two channels and three channels, it is customary to call the first "phantom", the second "hard" center.

Posted by Rick Long (Member # 213) on 04-08-2003, 09:01 PM:

My sincere apologies, Micheal. I did indeed read, and copy your post for future use.

As for the second post of mine, I admit it was after the show, and, feeling patriotic, I spent the late part of the evening with my friends Canadian Club and Canada Dry.

In any event, thanks to all who replied.

Now could someone point me East?