DTS/DD vs. CD Audio quality-opinions?

[Sir Terrence the Terrible]

First I must say that while this is kind of interesting to compare all this, it really is a BAD test for so many reasons.

First to be more accurate in comparing these codecs, stereo versions of Dolby, DTS, and CD at max bit rates would be more fair. That isn't possible, so it's a funky way to compare everything at best.

Tony, in theory you are correct, however if you were to encode only two channels of Dts at full bit rate, it would be lossless when compared to the CD max bit rate. Dts carries a bit rate of 1.411kbps for the 44.1khz platform divided between six channels. CD also carries a maximum bit rate of 1.411kbps but with only two channels. With only two channels in operation, that would make Dts a coder, instead of a encoder. Dts could make a bit for bit copy without any loss whatsoever. Dolby digital in its current form is fixed at 192kbps per channel(384kbps total) in its two channel mode. So there is really no way in this case to make a fair comparison without compromising something in the process.

[quote]Next, it wasn't clear just what kind of Dolby and DTS tracks were compared. There are a lot of numbers being thrown around, but they are not set in stone. Yes DTS has a max bit rate of 1.5mb, and DD 448, (the higher one is never used). But for movies the 1.5mb rate is RARE! The rate most commonly used for DTS video is the 754K rate, not the 1.5mb. The max DTS bit rate on a movie would absolutely smoke up space like you wouldn't believe.[\quote]

You are correct about the variable data rates used on DVD. However depending on the length of the program, and how many audio tracks, Dts does occasionally use the full bit rate of 1509kbps for music video DVD's. DVD's that have classical music with video almost always use the highest bit rate.

No studio that I know of uses the 384kbps data rate for DD movies anymore. All the studios at the behest of Dolby use the 448kbps data rate now. Yes Dts full bit rate is a space hog on DVD's, but that can be conquered by using DVD-9, 14, 18, and a higher expense of course.

Next, the max for DD is 448, but the 348? rate is quite common as well.

Actually its the other way around as I stated above.

[quote]When comparing DTS to anything it should be made clear what kind of DTS disc is being used. If it's a concert DTS title, it might run at the 700+ K rate, not the max. A DTS music CD does run at over 1.4mb and that rate is fixed.[/qoute]

When you speak of concert titles, Dts could run at both rates. I know a few of their classical music videos do run at 1509kbps.

As for the compression techniques used, it goes far beyond simply being technically lossy. There are other tricks going on to compress the data while making the fewest changes to the sound (that can be percieved). I bet most people don't know that DD is no longer stereo past 15kHz. To save space, sounds above that become mono. Many would argue that at 15k sounds aren't as noticable. DTS has many similar tricks as well.

DD is no longer multichannel above 15khz, not stereo. But an argument could be made that its bit sharing process doesn't exactly make is discrete in the true since of the word. The only "tricks" to be found in the coherent acoustics codec is the roll off above 15khz at the 754kbps data rate to save data space. For film sound, that is not a problem at all. But for music this could present a problem for instruments with lots of high frequency harmonics or overtones.

[quote]I tend to shy away from DTS, MP3 etc based on theory alone. The very basis of these codecs is to CHANGE the sound to make other things possible. Whether or not I or anyone else can tell is kinda beside the point. For DVD movies DD and DTS work just fine. But in the case of music we now have SACD and DVD-A, so the CD vs DTS thing is Soooo late 1990's. Sorry I couldn't resist ;0)[/qoute]

You have a huge misunderstanding about how codecs work if you think they are designed to "change" things. The purpose of an audio codec is to more efficiently encode the audio, with little or no change in audio quality. Some audio codecs are better than others at reaching this goal. Dts IMO is the best because at its highest data rate, it A/B's with complete transparency when compared to the printmaster tape. No other codec(including half rate Dts) can do this. Both DVD-A and SACD still do not have nearly the market penitration of CD, DD, and Dts, so its not really soooo late 1990's to make this comparison.

[sslabs]

All points taken, but I still hold to the fact that DD, DTS and MP3 change the sound, in fact they all do, and the results can be measured, and in fact they have been discussed at great length many times in magazines and on the net, whether we can tell is another story. To say that I don't understand how codecs work, and that they merely pack the data more efficiently seems a little defensive rather than anything based on fact. MLP for DVD-A is a way to pack data more efficiently without currupting it. DD, and DTS are not.

By just pointing at how DD and DTS go from stereo to mono at certain freq ranges proves that the original input sound has been manipulated to something else. I need not point to another fact to make that point. But I'm not saying that it means it will sound horrible, just that it goes against what everyone here (I think) is about, being an audiophile.


Not trying to start a flame war here, just my honest feelings.

As for the 192K stereo rate for dolby, I believe you are incorrect to double the number.

When the data rate is displayed at say 348 that's for all six channels (5.1) when that rate is displayed for stereo, (192) that should be the total, or 96k per channel, isn't that correct? I could be wrong but that would seem to be right.

As for market penetration, DTS shouldn't even be in the argument. There are more DVD-A and SACDs floating around out there than DTS music CDs.


Anyway, great conversation starter, but an uneven test at best. But I must admit that in this case it's all about the 'conversation' otherwise nobody would be hangin' out here at all right?






- Tony

[jeskibuff]

Someday, if I ever get the time (seems to be in short supply these days), I plan on dubbing some hi-res DVD-A and SACD stereo tracks to a recordable CD. Then, play the original source and the recording back simultaneously, volume matched to provide a good A/B comparison. This seems about the best way to compare the difference between the formats, as we can't rely on the recording companies to provide us with equivalent recordings in various formats.

Sure, there should be an expected degradation of the signal due to the reconversion of the analog signal back to digital (for recording), then back to analog again during playback, but will that be more severe than the supposed "graininess" of the PCM format as described by vinyl afficionados? I anticipate that there really won't be a big difference, but I think it will be a good experiment. Has anyone tried this yet?

[Sir Terrence the Terrible]

All points taken, but I still hold to the fact that DD, DTS and MP3 change the sound, in fact they all do, and the results can be measured, and in fact they have been discussed at great length many times in magazines and on the net, whether we can tell is another story.

I will give you the fact that MP3 and DD do alter the sound, and yes its very audible. But I know for a fact the Dts at its highest bit rate does not audibly alter the sound at all. While the encoding process does alter the original wave form to a degree(that's what happens when you remove inaudible data), its only when it degrades the audio enough to be heard that it becomes an issue.

To say that I don't understand how codecs work, and that they merely pack the data more efficiently seems a little defensive rather than anything based on fact. MLP for DVD-A is a way to pack data more efficiently without currupting it. DD, and DTS are not..

I think you are misusing the word defensive. I am not defending anything. I am stating facts, and only facts. Now let's look at the facts; DD and Dts(to a lesser degree) does remove noise, redundant and inaudible signals, stuff we wouldn't hear anyway. Dts encodes the data that's left at 20bit resolution, DD and about 18bits. So I am correct in saying it more effeciently packs data. And by the way, it doesn't "corrupt" the data as you insinuate. MLP doesn't even belong in this discussion because it is not a codec, you can't "play" anything on MLP.

By just pointing at how DD and DTS go from stereo to mono at certain freq ranges proves that the original input sound has been manipulated to something else. I need not point to another fact to make that point. But I'm not saying that it means it will sound horrible, just that it goes against what everyone here (I think) is about, being an audiophile. ..

Dts does not at any stage go to mono. It is a true discrete system. Also, it might be a stretch to say encoding audio into DD and Dts is manipulating the signal into something else. You room acoustics do it, do you stay away from it?
The same notes are being played, encoding doesn't alter pitch or time, or change any performance aspect whatsoever. All they do is remove what you already cannot hear. If you cannot hear it, then the process is benign. What degradation that does occur(mostly with DD or Dts half bit rate to a lesser degree) is minimal, and room acoustics will probably mask that. I fear room acoustics more than I fear what is coming from the output buffer of a Dts decoder.

Not trying to start a flame war here, just my honest feelings.

No flame war here, feelings are good. Facts are better.

As for the 192K stereo rate for dolby, I believe you are incorrect to double the number.

No, I am very correct. Since I own a professional encoder and decoder from both DD and Dts, I am well aware of all bit rates supported by both formats

When the data rate is displayed at say 348 that's for all six channels (5.1) when that rate is displayed for stereo, (192) that should be the total, or 96k per channel, isn't that correct? I could be wrong but that would seem to be right.

You are wrong. When the data rate says 448kbps for DD, that is for six channels(studios do not encode film soundtracks at 384kbps anymore) For stereo, its 192kbps for each channel for a combined total of 384kbps. DD is scalable from 32kbps(for voice only) to 640kbps(no current decoder supports this data rate)

As for market penetration, DTS shouldn't even be in the argument. There are more DVD-A and SACDs floating around out there than DTS music CDs.

Wrong again. There are over 200 million Dts decoders out there to support not only movies with Dts encoded soundtracks, but those DVD-A, music video's and CD that contain Dts tracks. Last time I checked, there were only about 500,000+ DVD players sold world wide that are capable of playing either SACD or DVD-A disc. That makes it still a niche product. The software end does not drive the hardware, the hardware drives the software.

[sfunches]

i know this is an older post,but ive just got a chance to read it. in each response i have heard nothing of how the music was recorded in the frist place.each recording is recorded differently some use aad, ada ,etc. some of my favorites were in ddd and add. telark make some of the finest recordings around even their sacds have a better sound better than most.george duke records his cds in ddd and it is spetacular. stealy dan(donald f) often uses aad or add,which makes his recordings so warm and detailed. cassandra wilson recoreded a cd called (full moon daughter) that will test what you have, it is a excellent recordng. so sacd,dvda,dts and dd doesnt mean anything if the original is not a good recording. oh, if you have heard the fleetwood macs greatest hits, the sound is very warm and detailed because it derived from an excellent analog recording transfered to digital,but still staying faithful to the analog recording.

[Francois1968]

Just the other day I compared some DVD stereo recordings with the good old CD's and found the CD sounded way better. I played the DVD's on the Arcam DV88+ en the CD's on the Arcam CD192, both components were connected analogue.
DVD's played in DTS were louder than the CD playback, but not better.
In my opinion DVD and DTS is not really an improvement. In terms of a pure audio sound I prefere CD's.