Stereo TrueHD over SPDIF

[s162216]

Hi,

From what I have read on the internet, if I put a Bluray drive in my PC and use optical SPDIF, then windvd or powerdvd will downmix TrueHd or DTS MA to stereo PCM as there is enough bandwidth over toslink.
If this is true, whats to stop me from using Pro Logic II to create the surround sound again from the stereo PCM or will this not work.

Also will if this works will it only work over optical as at the moment my computers onboard Nvidia Soundstorm only has coax but there is a card I could get that has both optical and coax. I am assuming there will be no problems with HDCP though.

 

[rnatalli]

It is true. Optical does not have the bandwidth to carry all the channels and will downmix to 2-channel PCM. I suppose you can apply Dolby to it, but you aren't getting lossless, discrete sound that way.

 

[lsiberian]

The toslink used doesn't have the bandwidth, but I'm certian this is because of the receivers not the cable. That being said. The decision was to go with HDMI instead of higher capacity fiber. I think it was a good choice long term. Even with some of the issues HDMI has experienced. reducing the cables is an advancement IMO.

 

[s162216]

Should be Good Though

It is true. Optical does not have the bandwidth to carry all the channels and will downmix to 2-channel PCM. I suppose you can apply Dolby to it, but you aren't getting lossless, discrete sound that way.

Although it won't be discrete sound it will proberly be of quite good quality even if its not lossless.

Will this only work over OPTICAL though not COAXIAL as at the moment I only have coax.

 

[j_garcia]

I believe that optical and coaxial (which are identical in what they carry) are both capable of carrying the signal, but the specification and as mentioned, decoding at the receiver, is not there and won't ever be.

I tried lossless and TrueHD over optical and the resulting stereo does sound good, but it also sort of defeats the purpose.

 

[s162216]

Doesn't Really Answer My Question

I believe that optical and coaxial (which are identical in what they carry) are both capable of carrying the signal, but the specification and as mentioned, decoding at the receiver, is not there and won't ever be.

I tried lossless and TrueHD over optical and the resulting stereo does sound good, but it also sort of defeats the purpose.

But can COAX actually do this as well as OPTICAL????
As far as I know the only difference between the two is that light and a light sensor are used instead of electricity, but is there a difference in bandwidth???

 

[rnatalli]

Although it won't be discrete sound it will proberly be of quite good quality even if its not lossless.

Will this only work over OPTICAL though not COAXIAL as at the moment I only have coax.

What's the point of sending TrueHD then? You'd be better off using standard DD/DTS.

Coax and Toslink are basically the same when it comes to capabilities. They transmit data different and have a different connector. That's it really.

 

[sparky77]

I don't yet know of an encoder that can downmix to pcm encoded as ac3, otherwise it would yield a decent sounding surround mix decoded by PLII, as of yet the ac3 decoderonly handles dts and ac3.

 

[s162216]

I don't yet know of an encoder that can downmix to pcm encoded as ac3, otherwise it would yield a decent sounding surround mix decoded by PLII, as of yet the ac3 decoderonly handles dts and ac3.

Technically I can as my motherboard has Nvidia Soundstorm built in with an early form of Dolby Digital Live, so the sounds from will go to the reciever as AC3.

 

[lsiberian]

What's the point of sending TrueHD then? You'd be better off using standard DD/DTS.

Coax and Toslink are basically the same when it comes to capabilities. They transmit data different and have a different connector. That's it really.

I'm not sure on this. I think their are differences at certain lengths. If I had a choice I would go with a standard RCA cable using the coax plugs.

 

[s162216]

Thats good

I'm not sure on this. I think their are differences at certain lengths. If I had a choice I would go with a standard RCA cable using the coax plugs.

Thats what I would have to use anyway, as my motherboard only has coax unless I manage to find one of the Asus SPDIF cards that could be brought as an optional accessory and had coax and optical inputs and outputs.

 

[j_garcia]

I'm not sure on this. I think their are differences at certain lengths. If I had a choice I would go with a standard RCA cable using the coax plugs.

They are identical in terms of the digital data transmitted, both follow the same specification - as mentioned, the only difference is how they transmit it. Length could be a factor, but for all intents and purposes in the typical HT, it won't matter. I prefer coaxial because it is a much more solid connection type. I've never had a coax cable come out, but I have had optical cables fall out.