Dolby Digital or DTS?

[BOLTS]

Which is better? I recently upgraded my receiver to a Marantz which handles both. Previously I had an older Onkyo that only did Pro-logic or DTS 5.1. Some dvd's such as the recently released James Bond box sets handle both. Is one preferred to the other when both are available on the dvd settings?

[drewface]

a lot of people seem to prefer dts. i've personally found i enjoy dolby digital using my yamaha's "movie: spectacle" sound processing format the best.

the best answer you can get on this, however, is trying both yourself and seeing which you prefer.

[shane55]

I don't think it's a matter of personal taste. I believe DTS is superior because it actually has a greater bandwidth, higher bit rate, or something like that (It's late and I'm brain dead).

And yes, I have always been able to tell a difference. Watch the opening of Saving Private Ryan in one then the other. A marked difference both tone and clarity. Same is true with the LOTR series.

shane

[MichaelG]

I listen to a lot of DVD concerts. DTS is always clearer and has a better soundstage when it is available. I haven't tried DD with my receiver sound processing though.

Michael

[Dread Pirate Robert]

Which is better? I recently upgraded my receiver to a Marantz which handles both. Previously I had an older Onkyo that only did Pro-logic or DTS 5.1. Some dvd's such as the recently released James Bond box sets handle both. Is one preferred to the other when both are available on the dvd settings?

On a technical level, they are extremely different codecs, although sonically they both are about equally capable of representing movie soundtracks at the most common bitrates used for each (448 kb/s for DD and 754 kb/s for DTS--actually, DD is slightly superior at 448 and closer to equal at 384). DD is the far more efficient and fully featured of the two, but the additional features that try to make it the one-size-fits-all codec have hurt its standing among home theater enthusiasts and audiophiles, and in some cases really do affect sound quality, making the simpler DTS the format of choice for those with decent audio equipment whenever there is a choice.

The problems with DD's features are a bit convoluted, but let's see if we can get through this. First, there's "dialogue normalization" which in theory simply introduces a bias to the main volume control (i.e. -12 dB really ends up being -16 dB) in order to allow producers to maintain a standard volume level for dialogue, independent of dynamic range, so that people would supposedly never have to adjust their volume control when they play different material. This was considered important back when DD was being considered as the standard for ATSC, which it is today. The problem is that in practice, this feature is never used correctly, if it is even a consideration at all, and most DVD producers, like everyone else, use the default value of -4 dB. I guess from an engineer's perspective, it was a good idea to leave a little wiggle room in the default value (it can't go higher than 0), but in this case, it means that with all else being equal, most DD soundtracks are played 4 dB more quietly than their DTS counterparts in direct comparisons, which would make most perceive DTS to be superior. People have known about this for a long time, and can make the appropriate compensation, but some DD decoders unfortunately do not bias the volume control but instead use DSP to reduce the volume of DD soundtracks, which can negatively impact sound quality. In short, although well intentioned, dialogue normalization turned out to be a useless feature that never helps and sometimes hurts.

The other major feature that works against DD is dynamic range compression. This is actually quite a useful feature for some people under some circumstances, but if it is mistakenly left on or is unwittingly defaulted to some nominal value in a receiver, then with all else being equal, DD soundtracks are going to sound less dynamic than their DTS counterparts. This is a fairly well known issue, but it's still not that simple. For one thing, some decoders unfortunately do not even have an option to turn this feature off, only allowing one to select from High, Medium, or Low, which means that DD's dynamic range will always be compromised when played on such equipment. For another, as I've previously explained in another thread, there is a different form of dynamic range compression encoded as parameters in the soundtrack itself that enforce compression when mixing down to a phantom center channel. Producers can choose to have no compression in this case, but as you can probably guess by now, most simply stick with the defaults, and the defaults are non-zero. The end result is that those who use a phantom center--which include many discriminating audiophiles who have very fine equipment--will have compromised dynamic range, and will most likely attribute this failing to the limitations of the DD codec itself, when in fact all of these issues could have been avoided completely with proper encoding and setup.

Thus far, I have made the assumption that all else is equal--the original uncompressed soundtrack in particular--but in actuality, this is rarely the case. On DVD titles that have both DD and DTS soundtracks, the DD soundtrack is often compromised (before encoding) to be less demanding on lesser equipment, which usually means speakers built into TVs. One probable reason that this is done would be simple opportunity--those who don't have home theater audio equipment usually have no choice but to play the DD track (that's all their players can decode), while others will use the uncompromised DTS track if they care about quality. This has nothing to do with DTS as a codec, but that's certainly what the end result looks like. There are also marketing reasons for using a more impressive mix for DTS. One is that because when properly encoded and set up, DD and DTS are usually hard to tell apart in overall quality, giving DTS a different and better mix adds value to DTS as a feature that can be sold to the public. Some studios don't even try to disguise this practice on some titles, such as Gladiator, which has a new mix only on DTS; yes, it's a discrete 6.1 mix, so it's justified, but they could have used the new mix in 5.1 form in DD, and chose not to (this studio has a stake in DTS, by the way). One very interesting example to consider is The Lion King, which also contains the original mix and an extremely different and far more impressive-sounding new mix in which everything sounds so much clearer, as well as more dynamic and enveloping. This is so interesting because I've seen a number of people refer to the new mix as the DTS track, when in fact it is marketed as the "Disney Enhanced Home Theater" soundtrack, and is, in fact, encoded in DD. :D

I've gone into about as much detail as I think anyone can stand, so let me sum up the main points, in my view:

1) DD is often compromised for one reason or another, often deliberately, especially when a DTS soundtrack is also present, so when no details are known about the mixes and their mastering, one should always play the DTS soundtrack when given a choice.

2) DD is perfectly capable of matching or even exceeding the performance of DTS at the common, practical bitrates used...when properly encoded, that is. If a DVD of a movie with an impressive soundtrack only has a DD track, don't sweat it--if the producers care about quality, they'll give you the best soundtrack they can, and in these cases, it should be just as good as the DTS track they would have given you.

3) Use a good center speaker rather than a phantom center to avoid the pitfall of improperly encoded DD downmix parameters.


I don't think it's a matter of personal taste. I believe DTS is superior because it actually has a greater bandwidth, higher bit rate, or something like that (It's late and I'm brain dead).

DTS can have a bitrate as high as 1509 kb/s on DVD, in which case it operates in a different mode, and is clearly superior to DD at its maximum DVD bitrate of 448 kb/s (I don't know about DD at 640 kb/s, its maximum rate at the decoder). DTS should also sound superior on laserdisc at 1235 kb/s vis-à-vis DD at 384 kb/s on this format. That said, DTS almost always runs at 754 kb/s on DVD, in order to save space and bandwidth for the image, which forces it to make major compromises due to the lower efficiency of its encoding algorithms. DD at 448 kb/s easily measures better than DTS at 754 kb/s, and sounds better to me when properly encoded using the same master soundtrack (e.g. as on Fantasia 2000), however in the common case described above, the technical superiority of DD at lower bitrates is moot--with extremely rare exceptions, just select the DTS soundtrack when given a choice.


And yes, I have always been able to tell a difference. Watch the opening of Saving Private Ryan in one then the other. A marked difference both tone and clarity. Same is true with the LOTR series.

These are examples of using different mixes (Spielberg has a stake in DTS and New Line is a huge fan at the very least). The differences wouldn't be so pronounced, otherwise, and even in these cases are not nearly as pronounced as the differences between the two DD soundtracks on The Lion King (note that Disney, which also produced Fantasia 2000, referenced above, has NO stake in DTS [of which I'm aware]).


I listen to a lot of DVD concerts. DTS is always clearer and has a better soundstage when it is available.

I've found that DTS is most commonly encoded at 1509 kb/s in these cases, as opposed to movies, so for most concerts on DVD it really is a superior encoding, no question (not necessarily a superior codec in general, though--just throwing lots of bandwidth at a codec that's not doing much, relatively speaking ;) ).

By the way, DTS in commercial theaters is a completely different, less sophisticated format that doesn't even have a separate LFE (.1) channel (these effects are encoded in the surround channels and filtered out during decoding), so it's funny when I see people in other forums argue as if they were one in the same. :)

[chas]

Very informative reply Dread Pirate. Are you in the sound business?

[curtis]

That has got to be some of the best explaining I have read! Robert, who are you and what do you do? :)

[Dread Pirate Robert]

Very informative reply Dread Pirate.

Thanks, I hope that I got most of that right! :eek:


Are you in the sound business?

No, I'm a pirate, aren't I? Well, actually, I'm a software engineer...but I haven't gotten around to paying the shareware fee for the version of TextPad I've been using yet, so that sort of counts, doesn't it? Argh, matey...aaarrgh.... ;)

[shane55]

Mr. Dread...

Informative, concise and extremely detailed post.
Thanks!

shane

[MichaelG]

Wow Dread Pirate! That was an excellent explanation! Thanks for sharing your knowledge! I really appreciate it!

Michael

[drewface]

heh, i've noticed all your posts are usually quite lengthy, dread. thanks for all the info.

i got my system hooked up today at home and did a couple test runs with scenes from the lord of the rings (special extended edition), switching back and forth between DD and DTS. contrary to a comment you made in your post about DD tracks being played more quietly than DTS, i actually found the DTS to be softer (had to turn the volume up louder on the DTS mode to get the same perceived volume). i'm still undecided on which i prefer, although DTS did seem less harsh with the very high pitched effects like dragons shrieking and the like...

i think this is one of those things that everyone will have to experiment with and decide based on their personal preferences and the equipment they are using. i always used DD before today, but i'm gonna have to do some more comparisons before i make a final decision.

[Dread Pirate Robert]

That has got to be some of the best explaining I have read!

I'm glad it turned out so well, which is not always the case for me. :)


Robert, who are you and what do you do? :)

I'm not an audio expert and am still a neophyte at Hi-Fi audio, but codecs are right up my alley as a computer programmer. I've been involved in HT for a long time, although I've sort of disappeared over the past several years. I used to post as Robert Cook (my real name), although I go under a number of different user names now. :)


heh, i've noticed all your posts are usually quite lengthy, dread. thanks for all the info.

I know, it tends to drive people crazy after a while, actually. But enough about me....


i got my system hooked up today at home and did a couple test runs with scenes from the lord of the rings (special extended edition), switching back and forth between DD and DTS. contrary to a comment you made in your post about DD tracks being played more quietly than DTS, i actually found the DTS to be softer (had to turn the volume up louder on the DTS mode to get the same perceived volume).

Although I tried to cover as many practical points as I reasonably could, my post was mostly about the theory behind comparing these codecs, which assumed "all else being equal." If, for example, a more dynamic mix is used for DTS than DD, the dialogue and much of the rest of the soundtrack could be mixed at a lower level in the DTS master, which gives it more headroom to work with for especially bombastic effects, and consequently forces you to turn up the volume, even past where you'd have it for the less dynamic DD mix. This would especially be true if the DVD producer is knowledgeable and chooses to set the DD dialogue normalization to 0 dB attenuation, which an increasing number of them appear to be doing of late.

Obviously, this is a very complex issue, and one of my main points was that in cases like this, while DD at 448 kb/s is capable of the same dynamic range and a similar level of quality as DTS at 754 kb/s, in the end, it's DTS that almost always gets the "better" mix. From this you can probably infer that for most practical purposes, I consider DTS a marketing tool and a waste of space at 754 kb/s (just encode the best mix in DD and be done with it!), although it's great at 1509 kb/s when space and bandwidth allow. This doesn't change the fact that the DTS track should almost always be selected in order to hear the superior mix, of course.


i'm still undecided on which i prefer, although DTS did seem less harsh with the very high pitched effects like dragons shrieking and the like...

Well, this mostly depends on how the soundtracks are mixed, but DTS does begin to roll off the treble at 15 kHz, while DD at 448 kb/s is pretty flat up to 20 kHz. I can't say whether the latter makes a difference in this case, since most people can't hear much past 15 kHz in any case, but there are differences in how the codecs handle certain sounds, and some people may slightly prefer either to the other. At least on paper, DD at 448 kb/s is relatively well supplied with bits most of the time, while DTS is starving at 754 kb/s due to the differences in coding. While it's quite possible that many if not most people would prefer the changes (based on a perceptual model of human hearing) that DTS is forced to make to the sound at half-bitrate, DD is theoretically and measurably making fewer changes.


i think this is one of those things that everyone will have to experiment with and decide based on their personal preferences and the equipment they are using. i always used DD before today, but i'm gonna have to do some more comparisons before i make a final decision.

That's good advice in general, although I'm pretty sure that most people who have home theater surround systems with subwoofers and enjoy the sometimes ridiculous dynamics of movie soundtracks would prefer the DTS tracks in virtually every case, if for no other reason than that better mixes are often used and they are never compromised for limited equipment, as DD mixes often are.

[clarke68]

Very helpful and informative post...with a little tidying up, you could sell that one of the home theater magazines for $1/word!

Quick question: how can I tell in what bitrate my DVD soundtracks are encoded? I've never seen it printed on the box, is there a website somewhere that puts out DVD publisher inside info?

Thanks!

[Dread Pirate Robert]

Very helpful and informative post...with a little tidying up, you could sell that one of the home theater magazines for $1/word!

Thanks for the kind words. Hmmm...just thinking about that second thing you said.... :)


Quick question: how can I tell in what bitrate my DVD soundtracks are encoded? I've never seen it printed on the box,

My DVD player happens to show the bitrate on one of its on-screen displays, and some receivers may do the same, so you'll want to consult your user manuals to see whether this feature is available. If it isn't, then there are other ways to tell that should not be discussed on public forums. ;)


is there a website somewhere that puts out DVD publisher inside info?

The following page has a fairly comprehensive list of DTS bitrates:

http://www.spannerworks.net/reference/10_6a.asp

Most 5.1 DD soundtracks have a bitrate of 448 kb/s, which has been the case for a long time now, but 384 kb/s doesn't sound all that different most of the time, so it's not as significant as 1509 kb/s versus 754 kb/s for DTS, and I couldn't find any lists of DD bitrates. DD is rarely encoded with a bitrate lower than 384 kb/s, although I have seen 256 kb/s on some documentary titles.