Film-Tech Forum ARCHIVE: fathom sound only coming through 1 channel

This is topic fathom sound only coming through 1 channel in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=16;t=003800

Posted by David Gibbons (Member # 10887) on 09-18-2019, 08:50 PM:

as stated whenever we play a fathom event we are only getting audio through the right center speakers. this was setup before i became involved and its set up with HDMI to the projector. at the newer theater i was able to run an optical cable from the hopper to the sound rack but the other two theaters sound rack do not have optical in. also this isn't the greatest solution because before and after the movie has played the optical cable needs to be plugged in/unplugged or else the audio will still continue to play. is the setup with HDMI going to projector the correct way it should be setup?

Posted by Marcel Birgelen (Member # 6801) on 09-19-2019, 05:49 AM:

I've never seen one of those Fathom Events player boxes, but what I've heard about them is that they're essentially cheap, off-the-shelf streaming boxes.

But maybe you can explain your setup a little, like what projector or more importantly, wat IMS/server and sound processor you're using, that would help debugging the situation.

Personally, I'd start by connecting a known-to-be-good device to the HDMI port, like a Blu-Ray player and check if the surround sound is working as expected. This gives you an indication where it's going wrong.

Posted by David Gibbons (Member # 10887) on 09-19-2019, 10:22 PM:

yeah i guess that would be helpful wouldn't it lol. we have a combination of christie 2210,2220 and 2230 projectors and cp650 and 750 processors. as far as the imb i am not 100% sure but i will post that info when i can tonight

Posted by Paul Finn (Member # 10726) on 09-20-2019, 07:29 AM:

I have seen the Barco DP2K-20C only output L & R AES audio from the HDMI input. Maybe others are similar? With the CPs here, I would consider using the ext. six channel analog inputs sourced from an AV receiver or OPPO Blu-ray player with 5.1/7.1 analog outputs. Remove the HDMI audio in the receiver/player from the HDMI downstream output and only input HDMI video to the projector. I assume there is either two channel or 5.1/7.1 HDMI audio from Fathom.

Paul Finn

Posted by John Thomas (Member # 6509) on 09-20-2019, 11:15 AM:

The typical Fathom setup I have seen is an optical cable from the Fathom DVR to a USL ECI-60 (basically a DMA8) provided by Fathom, which outputs your 6-channel analog over a straight-through DB25 into the processor's 6-channel analog input. Video comes out of the DVR over HDMI and plugs into the projector's native DVI ports. No IMB involved at all.

If you are running the audio through the IMB's HDMI input then it is typical that only stereo PCM is happening. To only be getting the Right channel may be an indication that your Left channel isn't working at all, so I would suggest running a Channel ID DCP or pink noise from the processor to be sure that that the Left channel is working.

It's also possible that the source content may have only been 2-channel.

In any case, I would avoid trying to run audio through the IMB's HDMI input. A USL ECI-60 or a Dolby DMA8 or DMA8+ would be ideal here.

Posted by Bruce Cloutier (Member # 9615) on 09-20-2019, 03:23 PM:

I remember when you plugged into the RED jack and into the WHITE jack and there was instantly sound! And, always sound! Well, I guess, once and a while a cable went bad and you had a ground loop or some interference. This HDMI thing drives me nuts. It's cost me thousands updating equipment trying to get both 4K and sound reliably through everything. They kept changing the standard and the encryption. I finally gave up. It's my home theater and the finance minister started being a bigger concern. So, 4K content with awful stereo or 2K (nicely upscaled) with 9.1 surround. Beer helps.

Posted by Scott Christopher (Member # 834) on 09-21-2019, 09:49 PM:

I can confirm the Christie CP2210 with Doremi IMB does reproduce 6ch via HDMI.

Posted by David Gibbons (Member # 10887) on 09-22-2019, 08:24 PM:

scott any idea how to set that up, ive tried just about everything i can think of to make it work

Posted by Carsten Kurz (Member # 5396) on 09-23-2019, 10:53 AM:

I guess, in a case like this, as Marcel stated, I would first try to connect a different HDMI audio device to the IMB HDMI input. As far as I know, the IMB software still does not support special HDMI audio routing, so, whatever is set in general AES audio routing on that Doremi will be used for HDMI as well. Which SHOULD be okay for general setups.

Maybe you have a windows notebook with HDMI at hand. These will nowadays be able to output LPCM audio with the image. Windows has a simple setup GUI to configure the HDMI out to multichannel, and play test sounds through each channel. Maybe that will tell more. Have you looked into the HDMI/audio setup of the Fathom box, is it accessible at all?

I would assume this auditorium uses a CP650 (as CP750 do offer a TOSLINK/optical inout). If the CP650 is equipped with a CAT790/778, you may use the optical output from the Fathom box if you use a cheap TOSLINK->S/P-DIF(coax) converter box.

Normally I would prefer HDMI audio, but in this setup, Doremi IMB passthrough, routing issues and CP650, it may be wonky.

- Carsten

Posted by Dave Martinez (Member # 11013) on 09-24-2019, 09:14 AM:

David,
I am in charge of Technical Operations at Fathom Events. I will PM you with our contact information so we can assist with this issue.

The main problem is that the Doremi IMB does not have the ability to decode AC-3 Dolby Digital and the reason why only two channels of audio are being heard.

All Fathom content is delivered in AC-3 so a Dolby Digital decoder is a must in order to receive all available audio channels.

For the rest, our standard is generally to use the Toslink output to the Cinema Processor directly. We generally do not like to use HDMI direct due to the audio delay issues caused by the decoding. This is similar to what happens with using the HDMI input on a home monitor and then needing to adjust the delay due to decoding.

Thank you!

Posted by Bruce Cloutier (Member # 9615) on 09-24-2019, 11:14 AM:

Hello Dave, welcome to the forum!

Posted by Dave Martinez (Member # 11013) on 09-25-2019, 01:55 PM:

Thank you, Bruce!