Dolby True HD 2.0 channel??

[admin_exported]

I'll start by saying how much I enjoyed the show and how much I was impressed by the What Hifi demo with the clip from 'Transformers'. I first put this question to the guys who did the demo (sorry but I can't remember your names), and they told me to put it in a post to remind them, so here it is:

I understand that on a standard DVD player, the analogue two channel (left and right) audio outputs are capable of outputting a 2.0 channel form of Dolby Digital; 'downmixed' in terms of the number of channels but not in quality. I have been wondering about the analogue two channel outputs on a HD-DVD or Blu-ray player that is capable of the new HD audio formats; Dolby Digital Plus, DTS HD, Dolby True HD, etc. What I would like to know is whether they can output a 2.0 channel version of an HD format; so that the higher 'HD' quality of the sound is retained - just without it being surround sound, or, if they completely 'downmix' the signal to the ordinary and lower quality (non HD) Dolby Digital stereo.

I would much appreciate knowing the answer to this as I am planning on bringing high-def vision to a fairly small room, and think that 2 speakers is the maximum for the amount of space I have. I also very much value the quality of my stereo music, and have previously found that even a stereo hifi seperates system can still produce a 'big' sound for movies.

 

[Anonymous]

Alright I've just read my post again and its kind of long winded so here's a simplified version:

What type and quality of signal exactly comes out of the 2 channel (left and right) analogue audio outputs on a Blu-ray or HD-DVD player? Could it be a 2.0 channel version of one of the uncompressed (or less compressed) HD formats (Dolby Digital Plus, Dolby True HD, etc.) which could be plugged into the aux. input of a stereo amplifier and still have the higher resolution, dynamics, etc. due to it being (originally) of a higher bandwidth (like when the 5.1 or 7.1 outputs can carry HD audio to the multi-channel inputs of a non-HD decoding multichannel receiver)? Or will the player only output bog standard Dolby Digital stereo? Or an even lower quality than that?

If anyone from the What Hi-fi team could answer this I would be very grateful.

 

[Anonymous]

The question I'm asking is basically this:

What is the best audio format that can come out of the 2 channel analogue outputs on a Blu-ray or HD DVD player that has onboard HD surround decoding; Dolby Digital Plus 2.0? Dolby True HD 2.0? DTS HD 2.0? Or is this just wishful thinking? I just thought that if these players can output HD sound via their analogue 5.1 channel outputs, then it would (theoretically) be possible for them to output a 2.0 channel version. Or would it?

Please someone answer me. Nice one.

 

[Andy TW]

I believe that the analogue outputs are limited to "CD quality" 44/48khz PCM audio.However it should be remembered that the Dolby Digital and DTS formats used on DVD were compressed formats wheras some (all?) of the new HD formats use uncompressed PCM audio. Therefore the 2.0 output from the HD formats should be of higher quality compared to the 2.0 output you get with standard DD/DTS.

 

[Anonymous]

Andy were you just talking about the stereo analogue outputs? Because the 5.1 analogue outputs can't be limited to CD quality 44/48khz PCM audio, because I know that it's possible for an HD DVD or Blu-ray player with an internal Dolby True HD or DTS HD decoder to send HD audio, via its analogue 5.1 ouputs, to any multi-channel receiver with the corresponding analogue 5.1 inputs? And I know that those analogue 5.1 outputs are capable of sending higher than CD quality audio because at the What Hi-Fi demo at the show, they demonstrated a system in which Dolby Digital Plus was sent from the 5.1 analogue outputs of an HD DVD player to a the 5.1 analogue inputs of a receiver, and the sound was most certainly much higher than CD quality!

Anyway, why do the stereo outputs have to be limited to CD quality?

 

[Andy TW]

Sorry I got my digital and analogue stereo mixed up (many stereo digital connections are max. 48Khz).As an analogue connection the stereo outputs should in theory get the same higher quality audio as the 5.1 outputs. Any limitation in the analogue signal should be due to the components involved and not the (digital) frequency of the original signal.