Film-Tech Forum ARCHIVE: Dolby CP650 and DVDs Losing Audio

This is topic Dolby CP650 and DVDs Losing Audio in forum Film Handlers' 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=1;t=011826

Posted by Tim Schroepfer (Member # 8746) on 05-11-2015, 02:31 PM:

All-

I'm new to this world and I'm looking for your help with a recurring issue with playing DVDs. When I cue up a DVD for playback the CP650 locks onto whatever signal the trailers and or title menu on the DVD player is spitting out. When we hit the feature (which often has the audio encoded differently) we lose audio. If I unplug the input and plug it back in the CP650 locks to the new format. Is this normal? If so is there a way to force the CP650 to switch formats on the fly or do I need to setup a user present for each format regardless of if it is coming in on the same input?

Thanks for your help!

Tim

Posted by Mike Blakesley (Member # 26) on 05-11-2015, 02:55 PM:

I have a CP650 here and it doesn't "lock on" to anything unless it's told to by the automation, so you might have some kind of an automation issue. As for switching on the fly - it has the buttons on the front panel whereby you can do that. If you're playing a DVD it's probably set up on either the U1 or U2 buttons (or possibly NS, although not too likely). If you want to switch to digital cinema then that would probably be the "11" button.

I write all this assuming your CP650 is set up in a standard movie theater application -- if it isn't, then none of the above might apply, so your mileage may vary.

Posted by Marcel Birgelen (Member # 6801) on 05-11-2015, 03:17 PM:

It might be worth explaining to us how your DVD player is hooked up to the CP650.

Also, make sure your DVD player isn't switching outputs between formats. Most menus are just plain stereo, whereas features often carry a Dolby Digital or DTS track or even multiple tracks. Maybe your DVD player switches to something like S/PDIF once it hits one of those formats.

Posted by Mike Blakesley (Member # 26) on 05-11-2015, 03:38 PM:

Good point - the problem could be in the DVD player itself. In fact I'll bet that's the problem, more likely than an automation problem.

Has the system been running correctly up to this point or has this problem been continuous?

Posted by Steve Moore (Member # 4753) on 05-11-2015, 03:54 PM:

What exactly does the CP650 lock onto when you unplug and re-plug? Having not used a 650 and gone from CP65s to CP750, I don't know if it works the same way; but the issue i get is that in the UK all our trailers are in Dolby digital, but features (if blu ray) are DTS only, and the CP750 wont do DTS, hence I get not audio on a feature.

My only option is to switch my player so DTS sends over the digital lead in stereo, hence the CP decodes in pro logic or send it to a separate DTS converter I have and send that into the CP750 in multi in analog.

I was just wondering if this is a similar issue you have here.

Posted by Tim Schroepfer (Member # 8746) on 05-11-2015, 04:10 PM:

All-

We strip audio from HDMI which then goes S/PDIF into the CP650. The problem as far as I can tell is with the CP650. As far as I know the CP650 has always done this.

We are a multiuse venue (1905 Vaudeville house) and host theater and film events. We have a discreet film system from our theater system and my understanding is that the film component is setup as was common and standard for the mid 2000s.

When the error occurs our Denon Blu-ray players indicate on the front panel that we are switching audio formats as we transition from trailers/ top menu to the actual film content. My desire is to have the CP650 just sense the new format and roll with it, but perhaps this is not how these units are designed? Perhaps I need to program one of the user format keys to be the proper format for the film and key it when we transition?

Sorry if these are very basic questions. I come from video projection for theater and corporate events and the Dolby is throwing me.

Thanks!

Posted by Scott Norwood (Member # 30) on 05-11-2015, 05:25 PM:

Are you using format 80 ("master digital in") on the CP650? This should just work, although some CP650s will make a "pop" when they start receiving word clock on the digital input. Note that the digital output of the player needs to be set to either "bitstream" or "PCM," though I can never remember which (you may need to try both).

Honestly, the best way to do this is to get an Oppo Blu-Ray player or any other player with a discrete 6-channel analog output and connect that to the external 6-channel input on the CP650. That solves a bunch of problems at once and the Oppo (and some others) will decode DTS tracks internally.

Posted by Marcel Birgelen (Member # 6801) on 05-11-2015, 05:54 PM:

quote: Tim Schroepfer
My desire is to have the CP650 just sense the new format and roll with it, but perhaps this is not how these units are designed? Perhaps I need to program one of the user format keys to be the proper format for the film and key it when we transition?

The CP650 isn't your average home receiver, it doesn't do much of the automatic format detection your AVR will. Furthermore, Format 80 on your CP650 will only take either plain LPCM or Dolby Digital AC-3 (and none of the fancy new formats, although they're also not supported over S/PDIF) via AES or S/PDIF. It will do nothing if you feed it DTS for example.

Like Scott mentioned, the safest way to connect your Blu-Ray player is via the 6-channel analog input on your CP650. Your player will do the decoding internally and you essentially got your "atomatic format switching". You should check if your Blu-Ray player supports this and get a proper cable. If not, consider buying a new player which will do it. The Oppo Blu-Ray player, while somewhat expensive for a Blu-Ray player, will do so.

This way, you will also bypass flaky HDMI->S/PDIF audio splitters. If the EDID negotiation on one of the devices fails (not uncommon), your player could end up trying to feed a format like Dolby TrueHD or DTS MA-HD to your converter/splitter, which will never work.

Posted by Stephan Shelley (Member # 8587) on 05-13-2015, 05:51 PM:

Another thing to check is to make sure digital mute is disabled. If it is enabled the 650 will only play ac3 in format 80.

Posted by Tim Schroepfer (Member # 8746) on 05-14-2015, 09:33 AM: