Film-Tech Forum ARCHIVE: Dolby E track configurations

This is topic Dolby E track configurations in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Scott Norwood (Member # 30) on 05-05-2013, 10:02 AM:

As with everything else, there are multiple standards for this, and some tapes are completely non-standard.

How does everyone deal with this in a festival environment?

The CP750 software makes it easy to switch the input configuration on the external 6-channel input (where the DMA8 connects), but it requires a laptop and isn't really convenient to change between shows. I don't remember if the CP650 allows for this or not (the only Dolby E tape I have played in a CP650 house was made to the Dolby standard). Older processors like the CP65 with the DA20 cable definitely do not.

I made a couple of DB25->XLR cables that could be used to connect a DMA8 to a cinema processor, and which would allow swapping channels by disconnecting and re-connecting the XLRs, but that seems clunky to me.

I'm mostly just curious as to how everyone else is handling this.

What makes matters worse is that few tapes have the track assignments written on the labels, and the only way to find the correct configuration is by trial and error (if dialogue is coming through the right channel, then the channel configuration is set wrong). I don't typically trust the information on tape labels, anyway, as the labs often get this wrong, but it would be helpful as a starting point.

Also, is there supposed to be a standard delay setting for Dolby E, or does it always need to be adjusted from tape to tape?

Posted by Steve Guttag (Member # 268) on 05-05-2013, 10:15 AM:

The CP650 should not be considered a Dolby-E decoder (and no you couldn't change the channel assignments)...the last version of the CP650 software that supported Dolby-E was 2.1.9.0 and remember, you had to have Dolby give you the password to turn the option on and that was dependent on the MAC address of the processor...it was going to be a $$$ option.

For our Dolby-E type customers, we generally have a Crestron system and the channel configurations can be changed via single button push. The three popular ones are already configured. You do have to use the DMA8 (Plus) input 1 to handle the channel reassignments.

Honestly, the standard 5.1 configuration is what I've encountered on 99.9% of the tapes that have come through (L/R, C/SW, Ls/Rs) in a 5.1 or a 5.1 +2 configuration.

As to delay...part of what Dolby E should bring to the table is keeping the audio latency under control since on the encode side, the encoders are designed to add audio latency to keep it in time with the video processing. A typical lip sync delay for Dolby -E tapes on DCinema equipment is on the order of 65msec. Again, via Crestron, we normally have delay buttons that increment in frames so the operator cna quickly adjust lip sync if there is an issue (with any video). If the tape is previewed then the correct sync can be written down and changed when the video is started.

Posted by Scott Norwood (Member # 30) on 05-05-2013, 10:18 AM:

To clarify: I was using a DMA8 Plus to feed the CP650 and CP750 through the external 6-channel input. I was feeding one of the BNC inputs on the DMA8 and using the CP750 software to change the input configuration for the 6-channel input. Probably not the best method, but it worked.

My need for this is for temporary festival screenings and special events, not for a permanent install, so Crestron and the like is out of the question (more-or-less).

Posted by Steve Guttag (Member # 268) on 05-05-2013, 09:50 PM:

If you have a DMA8 Plus...the Digital 1 input also has three preset channel assignments that can be swapped with just a point/click.

Posted by Scott Norwood (Member # 30) on 05-06-2013, 10:10 AM:

Hmm...the CP750 has a similar interface for reassigning the inputs on the analog 6-channel connector, but it seems cleaner and easier to do the channel reassignments in the DMA8 Plus itself.

I suppose that the best approach, then, would be to use the digital 1 input and have three buttons to select the preferred channel assignment by sending RS232 commands to the DMA8 Plus. That would solve the majority of use cases without needing a full-blown automation system. I don't love the idea of needing a laptop to do this.

Obviously, this would only work in environments where the DMA8 is not also being used for D-cinema D/A conversion....

- Scott