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    Invelos Forums->General: General Home Theater Discussion Page: 1  Previous   Next
HD-DVD Audio Stream Decoding
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DVD Profiler Unlimited RegistrantStar Contributortweeter
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Registered: June 12, 2007
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I'm in the habit with DVDs of putting them in the main player and cycling thru the audio streams to verify them.  My receiver tells me the format and number of channels in use.  I can easily distinguish between Dolby Digital 2.0 and DD Surround (Pro Logic) for example.

I'm getting ready to do an update to The Fugitive on HD-DVD and dropped in my player to do the same thing.  The jacket claimed English in DD 5.1+ with French and Spanish in DD 2.0 and an unspecified commentary track.

When i cycled thru the streams they all report as DD 5.1.  I put a different disc in and got the same results.  Is this an HD thing?  Are all tracks encoded as surround even though they might be using only some of the channels?
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DVD Profiler Unlimited RegistrantMark Harrison
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Registered: March 13, 2007
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Quoting tweeter:
Quote:
I'm in the habit with DVDs of putting them in the main player and cycling thru the audio streams to verify them.  My receiver tells me the format and number of channels in use.  I can easily distinguish between Dolby Digital 2.0 and DD Surround (Pro Logic) for example.

I'm getting ready to do an update to The Fugitive on HD-DVD and dropped in my player to do the same thing.  The jacket claimed English in DD 5.1+ with French and Spanish in DD 2.0 and an unspecified commentary track.

When i cycled thru the streams they all report as DD 5.1.  I put a different disc in and got the same results.  Is this an HD thing?  Are all tracks encoded as surround even though they might be using only some of the channels?


Up until recently, all HD DVD players decoded the audio in the player itself and sent it as a PCM stream to the receiver (if you use an HDMI cable).  So your receiver can't tell what type of track it is.  Some of the more expensive players have a new update that will allow them to stream the encoded track to the receiver for decoding (again, only over HDMI).  I think the XA-2, A35 and maybe the A30 will do this.

Of course if you're not using HDMI, then things are different.  If you're using the optical connection, then the tracks will always be decoded in the player before being converted to either DD or DTS then sent out to the receiver.  I don't recall which convert to DD and which to DTS, but I know the A2 will convert it to DTS.  I believe these are 1.5mbs streams.  I'm not too sure what happens with the analog outs.

So I'll take a wild guess that hooked up through an optical cable and I'd also guess you have an A3?  If so, you're getting a plain old DD stream sent to the receiver that is the downconverted DD+ or DD TrueHD.

For the record, I believe a lot of the Blu-ray players work about the same way, although at least a few can also sent the stream to the receiver for decoding.  So it's not necessarily an HD DVD issue.

So, if you have HDMI, the track may be decoded on the player or the receiver (if you have the right equipment).  Either way you're hearing the DD+ or DD TrueHD track.  If you're going out over optical, you're hearing the DD+ or TrueHD track deocded, then downmixed to DD or DTS (at a very high bitrate).
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 Last edited: by Mark Harrison
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Sadly this house is still and HDMI-free zone.

The HD player is an A30 and is optically connected to my receiver for audio.  The receiver knows both DD 5.1 and DTS but is too old to know DD+ or DD TrueHD.

I don't have any DTS encoded HD DVD discs yet so i can't test that, but it appears all the DD tracks, regardless of the number of declared tracks are converted to DD 5.1.

The A30 book says with respect to the optical output: When you play a disc recorded in Dolby Digital Plus or Dolby TrueHD format Dolby Digital sound is output.

I was just surprised the tracks claimed as 2.0 on the jacket were converted (according to the receiver) to DD 5.1 also.  A regular DVD converted all tracks to the expected output (5.1, 2.0, Pro Logic, etc.)

This only really interferes with getting confirmation of contribution info.  I would only listen to the (down converted) DD 5.1 tracks if available, and i've noted they sound better on the whole than my DVD audio tracks.

Thanks for the info.  Yours was much clearer than the manuals.
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DVD Profiler Unlimited Registrantstefc
Registered: March 14, 2007
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It's a problem with all 1st and 2nd gen HD DVD players, including the 360 add on. Basically when you set the player to transcode to DD 5.1 or DTS 5.1, it will transcode EVERYTHING into a 5.1 signal. So a 2.0 stereo soundtrack will be encoded as the front left and front right channels of a 5.1 signal (with the centre, rear left, rear right and LFE channels being completely empty) and it sounds horrid. This also happens with advanced mode commentary tracks that are 2.0 tracks mixed over the films main 5.1 soundtrack. The workaround I use for extras or films with 2.0 sound is to go into the 360's HD DVD settings and change the transcode setting to 2.0 stereo. This sends my amp a Stereo track and lets my amp engage a 2.0 matrix format (DPL II in my case) and gives the desired results.

I brought up the issue with Andy Pennell from Microsoft on his blog and once he understood the problem he ignored me and felt "I was hearing a problem that no one else in the world is bothered by". 

I'm guessing the problem will occur over HDMI too due to HD DVD's advanced mode authoring that requires sound mixing to happen in the player before it gets encoded to PCM and sent to the amp.

I'd be interested to see how the new players that allow raw bitstream output to capable amps over HDMI will work with advanced mode mixing, my guess would be that it will only output the 2.0 commentary track and not the main 5.1 film track. I'm setting up an Onkyo 875 + Samsung BDU5000 for a friend after Xmas so I will know soon enough.
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