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Dolby TrueHD vs. DTS-HD Master Audio on HD DVD/Blu-Ray (1 Viewer)

Dan Hitchman

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All of Sony's Blu-Ray titles (and the early MGM and Lionsgate titles via Sony), some of Disney's, and I believe, all of Warner Brothers.

They need to be consistant... they need to be master grade lossless!
 

DaViD Boulet

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Actually, I think that almost all of the 16 bit Dolby Digital Plus and Dolby True HD encodings on HD DVD and BD are downconversions from higher-resolution source PCM masters. Most mixing/mastering has been in at least 20/48 for quite a few years. Oh, I see (after posting) that Dan just said more or less the same thing.
 

cegko

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Originally Posted by Pete T C

Although we haven't heard any DTS-HD Master Audio lossless discs yet, I'd like to get everyone's opinion on which codec they prefer in terms of theory.

Here is how I understand it. First, Dolby TrueHD (being based on MLP) is not backwards compatible with Dolby Digital Plus/Dolby Digital, meaning that if you playback a TrueHD signal on a device without TrueHD decoding you will get no sound even if that device has standard DD decoding. DTS-HD Master Audio is backwards compatible with DTS, meaning that if you playback a DTS-HD Master Audio soundtrack on a device without DTS-HD Master Audio decoding, you will get standard DTS sound so long as the device can decode standard DTS - but at what cost?

Let's say "X" is the Master.

Dolby TrueHD encodes "X" into a lossless signal which is decoded by a TrueHD decoder during playback. Fairly straightforward.

DTS-HD Master Audio encodes "X" into a lossy signal "Y" and stores the information normally thrown away during lossy encoding as "Z". When played back on a standard DTS decoder, all you hear is "Y", and "Z" is ignored. When played back on a DTS-HD Master Audio decoder, "Z" is added to "Y", theoretically giving you the original signal "X" (hence lossless). One big problem I see with this. Since Standard DTS is a lossy signal, it is likely some artifacts will be present in the lossy "Y," however those artifacts obviously can't be removed for DTS-HD Master Audio since the original lossy signal "Y" plays the biggest role (I would wager 90%+ of audible information) in assembling the "lossless" signal. Therefore what you are essentially getting with DTS-HD Master Audio is [COLOR= rgb(255, 0, 0)]a signal that is not truly lossless[/COLOR], as the lossy signal is in reality the bulk of the the "lossless" signal and the artifacts in that lossy signal are carried over into the "lossless" signal. Also, despite this DTS-HD Master Audio actually takes up more space than Dolby TrueHD.

Despite its appearance of being inferior sonically on paper, DTS-HD Master Audio's backwards compatibility is a massive booster to that format on Blu-Ray as Dolby TrueHD decoding is *not* mandatory for Blu-Ray players. Because of this, studios will hesitate in using TrueHD on Blu-Ray releases, since there will be no standalones that can actually play the tracks. However, by using a DTS-HD Master Audio track Blu-Ray studios can placate both the customers who want "lossless" sound while ensuring everyone will at least get Standard DTS. This has already happened, with several Fox titles set for DTS-HD Master Audio on Blu-Ray and zero TrueHD titles. On the other hand, with HD DVD we already see many TrueHD titles since TrueHD decoding in the player is mandatory on HD DVD.

So, while DTS offered higher bitrates that generally resulted in better sound on standard DVD, in the high definition realm their codec falls significantly short of Dolby's IMO. Thoughts?
htf_images_smilies_smile.gif
...I have to confute the statement in red...

Hi everyone,
I don't know if someone has already mathematically tried the "lossless" compression of DTS Master Audio, since the criticism made on the type of this compression (lossy core + stream extension), and I know it may be more useful to geeks than to normal people, anyway i'm writing this post to blow every doubt away.
I started with the decoding of a multichannel FLAC Track (5.1 96 kHz 24 bit) into separate wavs, with eac3to 3.24. After that, I encoded the 6 tracks into one .dtshd file, with DTS Master Audio Suite, and, after having removed the "bad" header from the dtshd file (making a demux of it with tsmuxer, in order the output to be recognized by eac3to), I extracted again the 6 tracks, now from the new dtshd file, with eac3to (using Arcsoft DTS decoder).
The surprise was: the 6 original tracks weren't identical to the new ones, but I didn't stop here.
Using Ultraedit, I opened both the left channel tracks (obviously, it could be any of the 6!) and I noticed a lot of null bytes at the beginning of new.L.wav...
Moreover, I performed a HEX search of a random 16 byte string of the old track into the new one, and the seek was successful. So, I tried to remove all the null bytes at the beginning of the new track. Now, the only difference present after an eye-comparison were two bytes of the WAV headers (that were a "(" in the old file, compared to a "@" in the new one). After replacing one of the two symbol with the other (in both bytes) and saving the modified file, a check on the file dimensions and a MD5 checksum made me sure the two files were now physically identical. Ergo, [COLOR= rgb(0, 0, 255)][SIZE= 18px]DTS MA is truly lossless[/COLOR][/SIZE], despite the 2 different bytes in header and the "enormous" and useless zero-padding at the beginning.

Even better, DTS MA, contrarily to every expectation, [COLOR= rgb(255, 0, 0)]effectively takes up less space than Dolby TrueHD[/COLOR]: in fact, TrueHD uses a lossy core, plus the TOTAL information encoded in MLP Lossless, without a smart stream extension (try it yourself if you don't believe it... I saw this comparing DTS MA with 1536k core and TrueHD with 640k core).
So, if someone is still confused between lossless HD audio formats, this can bring to the conclusion they are totally equivalent for keeping the original audio signal.

In attachment the screenshots of the operations made...

Regards


DTS Really.zip1251540k .zip file
 

Todd Erwin

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Dolby TrueHD does not have a lossy core, which is one of the reasons most studios have switched to DTS-HD MA, so they do not have to include and program a separate (and often hidden) lossy Dolby Digital track.
 

cegko

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sure... for "core" in truehd streams I meant the lossy embedded track...
 

MrHookup 1

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Jeff
I am enjoying the new Lossless Formats so far; but only have a handful of discs. I prefer the DTS HD Master Audio format. I am using my Integra DTC 9.8 Processor, etc. I would like to find more lossless discs, especially Concerts, Rock Music, etc. So far, I have Jeff Beck Live @ Ronnie Scott's (the best so far), Tom Petty & the Heartbreaker's MOJO, Rush Moving Pictures. Dolby True HD: The Dark Knight (Hits you like a hammer!) Please let me know about other lossless discs that you may know about in these catagories. Amazon, B & N, Border's does not seem to have their act togeather in terms of Lossless Discs. Big dissappointment.
 

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