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Dolby TrueHD

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Old 02-11-2008, 09:48 PM   #1  
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Default Dolby TrueHD

Can Dolby Digital Plus, Dolby TrueHD and DTS-HD decoding be passed through a coax or optical cable? Or only by HDMI cable?
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Old 02-12-2008, 08:34 AM   #2  
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By design it is passed through HDMI although in some cases it can be captured via coax or optical digital connections, depending on the equipment.
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Old 02-12-2008, 12:03 PM   #3  
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Originally Posted by Loves2Watch View Post
By design it is passed through HDMI although in some cases it can be captured via coax or optical digital connections, depending on the equipment.
Since when can Dolby TrueHD, Dolby Digital Plus, or DTS-HD signals be passed over optical or coax? I've read everywhere that these cables do not have a high enough bandwidth.

According to Dolby's web site (www(DOT)dolby(DOT)com/promo/hd/connector_diagrams.html), they only list Dolby Digital Plus or Dolby TrueHD as transmittable over HDMI or 5.1/7.1 analog (RCA).
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Old 02-12-2008, 03:25 PM   #4  
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My bad, I did mean analog 5.1 or 7.1. Please excuse the error.
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Old 02-12-2008, 03:38 PM   #5  
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Since when can Dolby TrueHD, Dolby Digital Plus, or DTS-HD signals be passed over optical or coax? I've read everywhere that these cables do not have a high enough bandwidth.
There is no reason why either optical or coax could not support these formats in terms of bandwidth.
Both cable types probably have at least 10 times the bandwidth capability of HDMI.
It's got to be codec and equipment related.

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According to Dolby's web site (www(DOT)dolby(DOT)com/promo/hd/connector_diagrams.html), they only list Dolby Digital Plus or Dolby TrueHD as transmittable over HDMI or 5.1/7.1 analog (RCA).
That was my understanding - the question is, what's the reason?
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Old 02-12-2008, 05:36 PM   #6  
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There is no reason why either optical or coax could not support these formats in terms of bandwidth.
Both cable types probably have at least 10 times the bandwidth capability of HDMI.
It's got to be codec and equipment related.

Nope, an optical cable only can deliver up to 1.5 Mbps. It is impossible to deliver lossless audio via S/PDIF. It really is the limitation of the cable. (bandwidth) Here is an awesome explanation of HD audio.http://www./news/show/Joshua_Zyber/H...Explained/1064

Last edited by Scoob; 02-12-2008 at 05:41 PM..
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Old 02-12-2008, 06:06 PM   #7  
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Bad link dude.
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Old 02-12-2008, 06:45 PM   #8  
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Yes, bad link - must say, I would like to read it - always willing to learn.

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Nope, an optical cable only can deliver up to 1.5 Mbps. It is impossible to deliver lossless audio via S/PDIF. It really is the limitation of the cable. (bandwidth)
Actually, 1.5Mbps is not "bandwidth" - that is "data rate", and they are very different things.

The fact remains that optical fiber will almost always have a much higher "bandwidth" than coaxial cable which will always have a much higher bandwidth than HDMI cable.

Point of information:
An average RG59 coaxial cable has a bandwidth of about 1.0 gHz.
The bandwidth required to carry a full 1080i HD signal (including audio) is about 35 mHz.
Coax has no bandwidth limitations as regards carrying a little audio.

The same signal capability applies to data rates as well.
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Old 02-12-2008, 07:04 PM   #9  
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Actually, 1.5Mbps is not "bandwidth" - that is "data rate", and they are very different things.
Sorry, let me rephrase. Optical cables cannot exceed a datarate of 1.5 Mbps. Therefore cannot carry lossless sound.http://www.engadgethd.com/2008/01/22...hd-and-dts-hd/
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Old 02-12-2008, 07:34 PM   #10  
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http://www.dtsonline.com/media/DTS-HD_WhitePaper.pdf Scroll down a bit , it spells it out here as well.
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Old 02-12-2008, 08:18 PM   #11  
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Sorry, let me rephrase. Optical cables cannot exceed a datarate of 1.5 Mbps. Therefore cannot carry lossless sound.
Clearly, the existing toslink standard/specification, or whatever seems to be limited to a datarate of 1.5Mbps -
not unlike the HDMI standard had "limitations" prior to 1.3a; what changed was not the HDMI cable, but the standard and certifications procedures and implimentation.

Also, I readily admit the I am not an authority on this matter beyond the basic knowledge that optical fiber has greater bandwidth and datarate capability than either coaxial cable or HDMI.
Which leads to my reiteration that it is not the "cable"; it must be other factors and I would like to learn more.

I believe toslink can provide implimentations at least up to 150Mbps - according to Toshiba:

http://www.toshiba.com/taec/componen...de/toslink.pdf

so what puzzles me is why the pundits tell us that the datarate is limited to 1.5Mbps - and I have not been able to find the answer.

Last edited by Scottnot; 02-12-2008 at 08:21 PM..
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Old 02-12-2008, 08:51 PM   #12  
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Quote:
Originally Posted by Scottnot View Post
Clearly, the existing toslink standard/specification, or whatever seems to be limited to a datarate of 1.5Mbps -
not unlike the HDMI standard had "limitations" prior to 1.3a; what changed was not the HDMI cable, but the standard and certifications procedures and implimentation.

Also, I readily admit the I am not an authority on this matter beyond the basic knowledge that optical fiber has greater bandwidth and datarate capability than either coaxial cable or HDMI.
Which leads to my reiteration that it is not the "cable"; it must be other factors and I would like to learn more.

I believe toslink can provide implimentations at least up to 150Mbps - according to Toshiba:

http://www.toshiba.com/taec/componen...de/toslink.pdf

so what puzzles me is why the pundits tell us that the datarate is limited to 1.5Mbps - and I have not been able to find the answer.
Well here is what I do know. When I used to have my HD DVD and Blu ray players hooked up via optical, I would select Dolby True HD via the menu and the core would only play.(DD 5.1) at a much lower bitrate. The same is true when you select DTS-HD Ma, only the core is extracted. (DTS) After reading extensively about lossless audio since April of 06, it is common knowledge in all of the publications that optical cables do not deliver lossless audio. Maybe optical cables in theory (if built to different specifications) could support it as you are saying, but I have NEVER read it in print. Maybe you should call Toshiba and ask them.......maybe they could shed some light on the subject. Also, I'm sorry that that link didn't work earlier. You should give it a read sometime. Just google "HD DVD and Blu-ray audio explained" by Josh Zyber.

Last edited by Scoob; 02-12-2008 at 08:55 PM..
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Old 02-13-2008, 08:16 AM   #13  
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Originally Posted by Scoob View Post
After reading extensively about lossless audio since April of 06, it is common knowledge in all of the publications that optical cables do not deliver lossless audio..
Agreed.

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Maybe optical cables in theory (if built to different specifications) could support it as you are saying, but I have NEVER read it in print..
Once again, it's not the cables - which have gigabit capability.
Obviously "one" of the limiting elements would be the "transceivers" used at either end of the cable; and I suspect that is the issue in this case.

Quote:
Maybe you should call Toshiba and ask them.......maybe they could shed some light on the subject.
Actually, page 10 of their product guide makes it pretty clear that the capability exists.
"Operating at a data rate of 15 Mb/s allows the modules to be used in
digital audio equipment such as DVD players, which uses a sampling
frequency of 96 kHz, as well as the conventional audio application,
such as CD players and mini disc players.
Since these modules conform to the JEITA digital audio interface
standard, they can be combined with existing digital audio TOSLINK
products."

Quote:
Also, I'm sorry that that link didn't work earlier. You should give it a read sometime. Just google "HD DVD and Blu-ray audio explained" by Josh Zyber.
Thanks, I was able to find it by googleing.
Josh seems to be well informed and a pretty good technical writer as well.
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Old 02-14-2008, 02:17 PM   #14  
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Guys, optical cable CAN transmit very high data rates. It is done in the professional world, where standard TOSLINK cables are used with ADAT equipment, providing 8 channels of 24 bit uncompressed audio using the same connector and cable.

The thing is that it is not implemented in our consumer equipment and is not a part of the new specification for the high end audio formats...

It is a mystery to me why consumer manufactures and Dolby / DTS have not implemented the ADAT standard. It is right there, can transmit enough channels and is dead cheap technology that have been around for the past 10 years in the pro world. Made simple, it is just a matter of transmitting the light different" in the same cable and connector as we know as toslink...

A reason might be that the ADAT standard can not transmit 8 channels of 96khz audio ( it can, but will be limited to 4 channels in a so called SMUX) maybe that was why they decided on HDMI to be the carrier?

Never the less, HDMI is genius and in a few years this will be on all consumer gear and we will love its simplicity of carrying picture, audio and control signals og pristine quality.
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Old 02-14-2008, 07:07 PM   #15  
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Never the less, HDMI is genius and in a few years this will be on all consumer gear and we will love its simplicity of carrying picture, audio and control signals og pristine quality.
And locked, pay for content as well as regional lockouts and other orwellian control measures to make the studios richer.
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