DTS audio on HDTV - AVS Forum
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post #1 of 18 Old 06-03-2001, 08:50 AM - Thread Starter
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I like the sound of DTS 5.1 more than DD5.1. Is it possible to broadcast DTS instead of DD on satelitte and ota HDTV broadcasts?
Thomas DiCecco

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post #2 of 18 Old 06-03-2001, 09:47 PM
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DD is the official standard in the ATSC spec., so I doubt you'll ever see DTS in terrestrial HDTV.

I guess the sat providers could do what ever they want but they'll probably stick to DD as well . . . especially since DD is generally a smaller bitstream than DTS.
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post #3 of 18 Old 06-04-2001, 12:02 PM
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we can't even get 5.1 most of the time. DTS is not even an option for any broadcast. So no, you won't hear it any time soon.

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post #4 of 18 Old 06-04-2001, 04:29 PM
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Hello DTV pals.

You're right that Dolby Digital is the accepted standard for ATSC transmission, but you're also correct that the satellite providers could go their own way and broadcast DTS format audio if they chose to. They don't do this for a number of reasons, among them the lack of DTS broadcast equipment.

The main issue with the DTS algorithm in a broadcast environment is that the DTS data stream does not offer the flexibility of Dolby Digital. On the hardware side, DTS does not manufacture broadcast equipment, or much of anything else either. Most of DTS efforts focus on their licensing business in order to incorporate their technology into consumer equipment, thus achieving a revenue stream (as does Dolby) from each unit sold that incorporates their technology.

Dolby Digital was chosen, and is used as the broadcast standard for terrestrial, cable and satellite transmission of DTV because of three key features:
1. It provides high quality audio performance.
2. As a more efficient coding algorithm it offers substantial bandwidth savings over either baseband PCM digital audio or DTS.
3. It is scalable both in data rate and number of channels encoded, from a single mono signal up to a full 5.1 home theatre presentation.

Additionally, Dolby Digital offers a function called "downmixing" for those folks who do not own a full-blown home theatre (also for use in in-flight entertainment applications) but still want to enjoy a DVD or digital television broadcast over fewer speakers than was optimally intended. To listen to a DTS track, a full-blown home theatre system is required.

So, if a satellite provider chose to broadcast a DTS program (disregarding the fact that the equipment does not exist to multiplex the DTS stream into their ATSC broadcast encoder or to demux the stream at the receiving end), this program would be exclusive to only those folks who owned a full-blown home theatre, and everyone else would be left out.

These issues were also considered when the DVD-V standard was adopted, making Dolby Digital a mandatory audio track on all DVD-Vs, even those carrying a DTS track! However, since DTS takes up much more room on the DVD than Dolby Digital, a DD track on a DTS disk is often a stereo representation of the same multichannel DTS track, and thus it is seldom possible to compare the two tracks on the same disk.

Of course these issues are independent of any perceived difference in quality between the two coding algorithms. That issue is somewhat controversial and subject to personal preference.

You are welcome to contact me directly if you have any further questions or comments.

Best regards.
Mike
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post #5 of 18 Old 06-05-2001, 10:59 PM
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Mike is right on target with his comments but I'd like to offer an open suggestion. DD5.1 could be much improved on the HDTV channels if the broadcasters and transfer houses would stop using extensive audio compression that reduces the dynamic range of the DD5.1 for HDTV broadcast. This is the reason why most movies with DD5.1 on HDTV do not sound as impressive as their DD5.1 DVD counterparts. I know we will not have dts audio on HDTV broadcasts but at least we could have better dynamic range a la DVD quality on the HDTV movies and music concerts.

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post #6 of 18 Old 06-05-2001, 11:30 PM
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I question the sound quality even on standard digital programming. Nascar racing is family event at our house and Fox regularly does the "crank it up" feature where the announcers close their pie-holes for a lap or two and all the microphones are opened around the track. We are supposed to be enjoying surround sound, but there isn't any!

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post #7 of 18 Old 06-06-2001, 07:59 PM
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Mike-

While what you said is correct as far as the theoretical side of dolby AC-3 encoding and receiver decoding is concerned but I have been told by dolby engineers at NAB, direcTV engineers, and a rep from DishNetwork that they all apply some line leveling compression to keep the volume excursions to a minimum. I'm not sure at what point in the decoded stage this is applied but it was my understanding that this compression is not part of the dolby process but sets the maximum dynamic range the transmission will achieve before encoding.
The guy from DishNetwork(Dan) told me they also have a demo loop channel that we cannot get that has a dolby DD5.1 with true non-compressed AC-3. It is available to dealers I understand but I have not been to a dealer that can demo that. He claimed that demo is true DVD quality but admitted HBO and Showtime and their PPV has some line leveling added. I also know that our cable company applies line leveling across the board on all channels. My cable tv channels all sound as uniform as AM radio!

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post #8 of 18 Old 06-06-2001, 09:42 PM
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While the cinema industry has had the advantage of providing multichannel audio for many years now, television audio engineers are still learning the appropriate techniques for multichannel mixing. One of the major challenges the broadcast audio engineer faces is that many of the broadcasts (NASCAR for example) are done live. This adds a bit of the "seat of your pants" factor to live multichannel broadcasts. It is understandable that live events use some amount of pre-processing prior to encoding into the Dolby Digital transport data stream, and could result in the audio compression you describe.

Keep in mind that the Dolby Digital encoding process performs no pre-processing on the original audio content whatsoever. Any dynamic range processing is user selectable and is performed within the decoder at home.

For full dynamic range listening, be sure to check your decoder or integrated amplifier to make sure that any dynamic range control is turned off. This feature may be called different things on different consumer electronic gear, so it's best to refer to your owner's manual. In general however, maximum dynamic range control (what we call "RF Mode" in the encoding world) is called "Midnight Mode" in many consumer electronics. A variable dynamic range mode is known as "Line Mode" in the encoding world, and can be called any number of things in consumer gear.

Also, bear in mind that if you are downmixing (i.e. listening to a 5.1 broadcast through a 2-channel stereo system for example), dynamic range control is automatically applied by the decoder to help avoid the possibility of clipping and distortion.

Regards.
Mike
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post #9 of 18 Old 06-07-2001, 11:25 AM
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Don, as I mentioned in my previous posting, broadcasters may add some preprocessing to the audio signal in order to prevent overloading. While this is common on live events, as you mention you may also encounter it on prepackaged programming. The Dolby Digital encoding process adds no preprocessing to the audio whatsoever, and any compression or other processing on the source audio prior to encoding is entirely at the mercy of the broadcaster's standards and practices.

I agree that prepackaged programming, primarily theatrical presentations, should require little or no preprocessing at all, and I would venture to guess that many broadcasters are unnecessarily performing the same routine audio processing duties that they have done on their analog broadcasts. Hopefully diligent and vocal consumers combined with responsible manufacturers like Dolby Labs can help to prod the DTV beast along the path towards full dynamic range digital audio presentations that rival the cinema experience.

Regarding Dolby as a monopoly, the very nature of standards require a uniform selection within a designated region. Around the world, the two competing digital broadcast standards are DVB and ATSC. Dolby Digital is compatible with both and is the standard for use in ATSC compatible broadcasts. The dts algorithm was not chosen for a number of reasons that I detailed earlier, but perhaps I didn't highlight a main reason: Their lack of participation or desire for inclusion in the broadcast standard.

dts has chosen to focus their efforts on licensing their technology in consumer equipment and not on manufacturing products. It's not a question of whether Dolby is a monopoly or not, the fact is that dts has chosen not to enter the broadcast market.

Personal preference aside, dts and Dolby Digital technology both sound good. It's just that Dolby Laboratories manufactures equipment for the professional broadcast industry as well as licenses it to consumer manufacturers. Therefore, Dolby Digital crosses more boundaries and is flexible for use in all the various applications found in digital television broadcast, DVD postproduction and cinema.

Regards,
Mike
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post #10 of 18 Old 06-07-2001, 09:14 PM
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I have a 7.1 (6.1) receiver and I enjoy the dts-ex over the dd for obvious reasons. Can dd be considered a monopoly on broadcasts and be forced to let dts and any other future formats get on board?

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post #11 of 18 Old 06-08-2001, 07:24 AM
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Mike,
thanks for the insight. Will there be any broadcasts on dbs of dd ex or dts ex?


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post #12 of 18 Old 06-08-2001, 07:40 AM
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Mike- I did not mean to imply that the dolby process does add compression in the AC-3 encoding stage. I have read your many pdf files on your equipment and understand exactly what you said, twice. I apologize if it came out that way. You did understand that the broadcasters, possibly the transfer houses and dub houses are the likely guilty parties in sabotaging the great DD5.1 dynamic range capability. It is unfortunate that when this compression is done to the audio before DD processing we have no way to remove it. I can also say that with respect to DVD's this is also the case but not in all. I have purchased some dts and DD5.1 DVDs just to make the comparison. One of the best comparisons was the dts and DD versions of Saving Private Ryan. I have both DVDs and I have a real tough time telling them apart as the DD5.1 nearly matches the sound of the dts version. I have others where the dts is strikingly different and one dts DVD where the dts is so bad "The Shadow" and the DD5.1 DVD is not good but a tad better than the dynamic range of the dts. To my way of understanding, this is simply an operator tinkering that we can not change as in the dolby standard.
While I don't wish to point out all the exceptions to the rule I have heard, I do agree with the original poster that dts, for the most part, offers a wider dynamic range on non-broadcast media than DD5.1. However, Dolby DD5.1 is the encoding that is the standard, therefore I feel that we all should concentrate on making the DBS and broadcasters give us all that DD5.1 can offer and I think those who want dts will be surprised at how much better it can sound if they allow the sound to pass from the film print to the DD encoder without pre compression/ expansion and limiting, dbx line leveling and whatever else they may have at their fingertips. We're not listening to Voice of America. Someone should give them a clue.

One other thing, Mike. When do you think DirecTV group in LABC will ever figure out how to spec their demo loop on channel 199 so that it is either DD5.1 or DD2.0 ? http://www.avsforum.com/ubb/frown.gif


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post #13 of 18 Old 06-11-2001, 12:21 PM
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Kipp:
Dolby Surround EX is not being used in broadcasts yet. It is a simple matter to include it at some point in the future, but for now we're helping the broadcasters to get on the air with 5.1, so we're going to lay off the EX stuff for now. There's no need to confuse the issue at this early stage.

Don:
Thank you for your considered response. I'd like to point out that comparing dts and DD soundtracks is quite a bit more complex than switching between tracks on a DVD. Ken Pohlmann wrote a very interesting article about this exact topic called "Dolby Digital vs dts...Which is better?" that is posted at http://www.soundandvisionmag.com/Sou...352_1,00.html.
There is also a link to the article on Dolby's web site at: http://www.dolby.com/pro/#guides.

It is important to realize that simply requiring more space does not make dts "better" than Dolby Digital. In fact, it is interesting to note that dts recently introduced an option whereby DVD authors can cut the dts data rate requirement in half (still more than twice Dolby Digital's data rate) by reducing the frequency response, leading a reasonable person to conclude that dts would jump at the chance to lower their data rate requirements if they could do so without seriously effecting the quality of their audio.

Dolby Digital is simply a more efficient coding algorithm, and that's not even getting into the cross-platform flexibility of the technology to be received and enjoyed in the home through the use of varied media.

Regarding our pals at DirecTV, I'm unaware of the problem you are describing, but if you'd like to contact me directly in more detail, I'll see what I can do to help get it straightened out.

Regards.
Mike
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post #14 of 18 Old 06-11-2001, 02:41 PM
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Mike, I sent you an e-mail giving you some background on what the problem is. If you want more specifics, let me know.

Thanks for the links, I'll get to them a little later.

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post #15 of 18 Old 06-11-2001, 03:26 PM
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>>Moreover, although other factors may have influenced my preference, in each of the four blind trials, with each of the three titles, using two different playback setups and two different main speakers, I consistently preferred source A. In the end, David revealed that version A was the Dolby Digital soundtrack.<< excerpted from your link.


Well the above paragraph explains how the whole test was flawed. We all know that the largest coloration to any sound, next to the listening room are the speakers. Why did they use two different main speakers? I think he was judging speakers, not dts vs, dolby digital preference.

MY preference would be to run the test in an intended listening environment with one set of speakers, amp, and two DVD players feeding this "preferred system" The reason is that the difference is admitted subtle. This means that the real proof is what it sounds like on your own preferred sound system. Level the playing field and then choose which sounds to your liking on your own listening environment.


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post #16 of 18 Old 06-11-2001, 05:04 PM
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Hi Don.

If you look at the article again, I think that you'll find that what Ken was speaking to in that excerpt is the fact that they performed the complete tests with two different systems in order to minimize the effect of any equipment preference.

Ken Pohlmann is a respected expert in the field of digital audio and the author of "Principles of Digital Audio".

Regards.
Mike
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post #17 of 18 Old 06-11-2001, 05:35 PM
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I understand. They used just two systems and felt that these two points were enough to justify the elimination of system preference. I don't think so! If you want to do that, many more systems must be run to make the claim that the difference is independent of systems. I will admit that one could safely say that in the two systems they chose to evaluate on the results were similar. My point was that with the variety of systems out more and different system configurations should be tested to be statistically significant, not just two. I just thought that part of the test was flawed. In the case of dts and DD there are only two being tested so no other variation need be considered. This is why I would have a preferred system and then run the A/B test. Then, which ever wins is the clear choice for that system. This is different than claiming a universal result. In my case the clear choice would be dts as the best way I can explain it is dts sounds more expansive, making the room sound bigger without artificial sounding reverberations. The worst dts DVD I have is The Shadow. The best DD5.1 I have is SPR but the dts version is considered a small fraction better. Both are very well done. I do treat my ears to the special dts versions of DVD's once in awhile and except for the movie The Shadow, I am rarely disappointed.

With DD5.1, I come to expect a standard of quality that doesn't change much. I know it is the most compatible and the broadcast standard for many reaons. I suspect that some of that expansive sound I describe has to do with some phasing as discussed in one of those articles. I also wonder if the bass of dts is peaked in the subsonic range which gives that blow you away feel. DD5.1 comes close to that in the SPR (Saving Private Ryan)

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post #18 of 18 Old 06-12-2001, 12:53 PM
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Hi Don.

Like my girlfriend who like anchovies on her pizza, I'm not going to say that your personal preference for dts is wrong.

If you look at Ken's article carefully, you will see that he comments on the difficulty and the extensive variables found in attempting to test the two algorithms in a blind manner. In fact, his results that you quote are given with disclaimers and reservations that you did not relay.

As Ken mentions in the article, to make a more careful and definitive evaluation of the two algorithms, more detailed testing is necessary. Indeed, up until just a few months ago, in order to encode a dts track an engineer had to take his source audio to one of about five locations in the country that had a dts-owned encoder. In contrast, Dolby has been selling professional Dolby Digital encoders and decoders for more two years now. This lack of dts hardware made Ken's attempt at evaulating the two systems nearly impossible, since the task he undertook was to evaluate the <u>encoding algorithm</u> and not the consumer equipment relaying it or the mixing techniques used in creating the source audio.

Now however, dts has made commercial versions of their encoder and decoder available for purchase. Hopefully with this new hardware, someone like Ken, or perhaps yourself, will make another attempt to resolve this controversial issue about which algorithm sounds "better" once and for all.

I for one, having had the opportunity to listen to both in a professional environment, think they both sound good, it's just that Dolby Digital takes less room to do it.

Best.
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