Film-Tech Forum ARCHIVE: Dolby True Hd over HDMI

This is topic Dolby True Hd over HDMI in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Paul Looker (Member # 5420) on 12-22-2014, 05:18 PM:

Hi all, we do a lot of kiddie shows for local youth groups and I have no problem with DTS HD Master audio, or any DTS for that matter, but when trying to play Dolby Audio the sound will be out of sync with the picture. I Have an NEC NC900C with a GDC IMB. And our processor is a USL JSD-60. I run the HDMI right into the IMB and run sound on the processor on the same channel as any normal feature with the audio output that is already coming from the projector. It says Dolby digital right on the processor so I figure there has to be some way. I can't figure what that way is though. Any thoughts?

Posted by Marcel Birgelen (Member # 6801) on 12-22-2014, 05:31 PM:

You should be able to configure audio delay per format in miliseconds in the JSD-60. Check the manual for the actual settings.

I suppose you're playing it from BluRay? So alternatively you can also try to set the lip-sync delay in there. Not all players support it but most of the better players do.

Posted by Harold Hallikainen (Member # 5405) on 12-22-2014, 06:28 PM:

Where is the Dolby Digital decoding taking place? The JSD-60 can decode Dolby Digital or DTS streams on the coax or TOSLINK inputs. If you're coming in AES, the decoding has to happen somewhere before that.

Harold

Posted by Paul Looker (Member # 5420) on 12-22-2014, 07:12 PM:

I feel like I didn't have any luck with the coax before. I will try it again though. I had been looking into toslink but I thought I saw on the net today that to slink wouldn't support the hd audio.

Posted by Chris Slycord (Member # 4239) on 12-22-2014, 09:28 PM:

Toslink doesn't support the HD audio formats. It supports up to 5.1. So you'd be stuck with Dolby Digital.

Posted by Harold Hallikainen (Member # 5405) on 12-22-2014, 10:39 PM:

And the JSD-60 with the DI-84 board supports basic Dobly Digital (AC-3) and basic DTS decoding. Since I doubt the IMB does any audio decoding, you may want to do the decoding to analog in the player, then use the JSD-60 6 channel analog input.

Good luck!

Harold

Posted by Steve Guttag (Member # 268) on 12-23-2014, 05:38 AM:

To the best of my knowledge...NOBODY's mediablock (IMB) will do DTS/DOLBY audio decoding, at this time. They can take in LPCM and that is it. As Harold says, it would have to happen upstream (say in your BluRay player). Furthermore, decoders like the Gefen A/V Pro III don't handle the high bandwidth audio either...you'll get the low bandwidth DTS or Dolby decoding (e.g. AC-3). To get the high bandwidth, you either need the source device to do the decoding (e.g. Oppo BDP-103 BluRay), use a consumer A/V receiver/preamp or (consumes massive rackspace but lots of bang for the buck), in the pro world, the Crestron HD-XSP (small, but only controllable by Crestron).

There are Cinema Processors that decode one or the other in high bandwidth. Datasat AP20 handles DTS Master Audio but only AC3 from Dolby...conversely, the CP850 handles Dolby True HD but no DTS on its HDMI inputs.

It is one reason I've moved towards using just the Oppo in smaller A/V systems (it has two HDMI inputs with dual HDMI outputs) or jump into using the Crestron HD-XSP for larger systems.

HDMI can be a pain...watch out for settings in your devices where it will let HDMI to set lip sync...this may be what is throwing your sync off if something is broadcasting something funny to make the source think it needs to apply some delay. Try to set your delay yourself based on actual tests. The EDID of each HDMI device in the signal path can also alter what you think you may be getting as each device gets to say what it is capable of handling and if the "Sink" doesn't call for Dolby True HD or DTS Master Audio...they won't be on the cable...it will be the least common denominator of ALL devices on the HDMI party line.

Posted by Carsten Kurz (Member # 5396) on 12-26-2014, 02:54 PM:

Some players can decode all multichannel formats to 6/8ch LPCM, they would then work with all audio codecs towards Doremi and Dolby IMB HDMI inputs. The problem is, this feature has no standard function name assigned, so you may have to dig into manuals or HomeVideoGroups to find out which player supports it.

BTW - some current LG or Samsung players have options to re-encode to either DTS OR AC3 for Toslink/SP-DIF output. So, there are solutions, even cheap ones, you just need to spend some time to find out which player best fits your needs.

And yes, if you spend some more money, an Oppo will leave no problem unsolved, after they finally decided to allow the OSD to be disabled completely a while ago.

- Carsten

Posted by Jarod Reddig (Member # 6363) on 12-26-2014, 03:30 PM:

Definitly agree on just getting an Oppo BD player.

Posted by Steve Guttag (Member # 268) on 12-26-2014, 08:06 PM:

Note, the Oppo does decode just about everything from BluRay...if you are using it as a decoder for something upstream...say a satellite receiver, it will only decode the low bandwidth audio on its HDMI inputs.