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Discussion Starter · #1 ·
I am reposting here some comments originally posted on another forum (probably "off-topic" in the original location). The topic is comparative listening to different areas of the Grateful Dead "American Beauty" DVD-Audio disk. (Original motivation for my post was that someone else reported hearing "distortion" of DVD-Audio recordings with the same player as mine, a Pioneer DV-578A, so I decided to try a subjective, "sighted", comparative listening test of DVD-Audio and other areas on a single disk.) The disk contains:


DVD-Audio: 24bit/96kHz 5.1 channel PCM

DVD-Audio: 24bit/192kHz 2 channel PCM

Dolby Digital, 5.1 channel

CD: 16bit/44.1kHz 2 channel PCM (on the flip side of the dual disk)


My previous comments:


The audio path was through the two-channel analog output of the player, via the "pure direct mode" of a Marantz 5500 receiver, to Beyer DT-880 headphones. I listened to several songs in stereo DVD-A, stereo CD, and 5.1 Dolby Digital downmixed to stereo in the player. I thought the DVD-A stereo version was absolutely outstanding. Vocals and instruments sounded much more lifelike and natural on the DVD-A than the other mixes, also the "headphone soundstage" was more realistic and less fatiguing on the DVD-A. In particular, on the CD, stereo separation effects seemed excessive, as if the vocalists were sometimes shouting in my left ear, sometimes shouting in my right ear, and were sometimes in the middle of my head (such effects are not unusual in headphone listening).


I don't believe my test was a true "format to format" comparison of DVD-A vs. Dolby Digital vs. CD, because each mix may sound different as a result of decisions made by the mixing engineers, rather than for reasons inherent to the digital format. I do think the test suggests that the stereo DVD-A playback on my player is free of serious problems.
 

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Discussion Starter · #2 ·
Krabapple wrote (in response to my post quoted above):

Quote:
I would think the DD mixes (if not the sound) would be the same as the DVD-A mixes, on the DVD-A disc, and thus it's available to anyone with a DVD player. My main concern in comparing them would be matching output levels (and ideally the comparison would be blind).

I'm aware that blind, level-matched, fast-switching comparisons (of different versions of a recording, or playback of a single recording on different gear) are considered the most accurate scientific tests of "hearing differences". But I'm not set up to do that, so I'm only reported subjective, sighted comparisons. And my player won't let me do "fast switching" between DVD-Audio and DD!


My previous comparison of the DVD-Audio 2.0 and DD 5.1 (on headphones) had a flaw: too many things were varying. In particular, the DVD-Audio 2.0 is a "dedicated" two-channel mix by recording engineers (in this case, including one of the original artists), while the DD 5.1 was downmixed to two-channel in the player, presumably following simple "one size fits all recordings" rules. So it isn't surprising that the "dedicated" two-channel mix (based on decisions by people who know something about the music and recording) would sound better than the player downmix (based on simple, preprogrammed rules).


I therefore did another comparison, listening to the DVD-Audio 5.1 through the speaker system in my room (via 5.1 channel analog outs on player to receiver), and listening to the DD 5.1 the same way (via coax digital out on player, with decoding in receiver). I agree that the "surround mix" (how sounds were divided among the various speakers) was the same (as far as I could tell) for DVD-Audio 5.1 and DD 5.1. But overall, the DVD-Audio still sounded noticeably better than the DD. What I mean is that, on the DVD-Audio, vocals sounded more natural (more like voices of people in the room with me), and acoustic instrumentals sounded more realistic and "detailed". On the DD, acoustic instruments (guitar, percussion, mandolin ...) sometimes had a "synthesized" quality. Further, the "contrast" in sound between electric guitars (on "Sugar Magnolia", for example) and acoustic instruments (on other tracks) seemed greater on the DVD-Audio than on the DD.


In addition, I discovered that I preferred to listen to the DVD-Audio louder (peak level about 84 dB) than the DD (peak level about 80 dB). The DD started to sound unpleasantly loud above 80 dB, while I wanted to turn up the DVD-Audio to better hear fine detail in the instrumental sounds. I was able to quantify my preferred peak levels because I had the Radio Shack digital SPL set up during the comparison. I listened to both the DVD-Audio and DD with peak levels between 80 dB and 84 dB, so the same range of levels was covered for both.


Finally, although it has probably been done posted before somewhere, I will post a comparison of the total bit rate (bits per second, all channels summed together) for the following digital formats:

(A) Multichannel DVD-Audio, with 96kHz/24bit 5.1 channel

(B) Hypothetical "CD quality" multichannel, 44.1/16 5.1 ch

(C) Dolby Digital 5.1 ch, maximum bit rate (on standard DVDs)

(D) Dolby Digital 5.1 ch, typical bit rate

I will also give variants of the higher-resolution formats, (A) and (B), that assume only 1% as many bits are used for the LFE channel as for the others. This is my idea, to give a fairer comparison of the "useable bit rate" for all channels summed together, because the LFE only needs to pass frequencies to 200 Hz, while the others need to pass frequencies to 20,000 Hz (hence it is "wasteful" to allocate as many bits to the LFE channel as to the others). Ratios of the bit rate for the other formats to the bit rate for the "CD quality" option will also be stated.


(A1) Multichannel DVD-Audio (with "full LFE"): 13824 kb/s

(A2) Multichannel DVD-Audio (with "1% LFE"): 11543 kb/s

(B1) "CD quality" multichannel (with "full LFE"): 4234 kb/s

(B2) "CD quality" multichannel (with "1% LFE"): 3535 kb/s

(C) Dolby Digital 5.1, maximum (on std DVD): 448 kb/S (all channels together)

(D) Dolby Digital 5.1, typical (on std DVD): 384 kb/S (all channels together)


RATIOS

(A1)/(B2) = 3.91

(A2)/(B2) = 3.27

(B1)/(B2) = 1.20

(B2)/(B2) = 1.00 [that's re-assuring
]

(C)/(B2) = 0.127

(D)/(B2) = 0.109


To summarize, DD provides a far lower bit rate than a hypothetical "CD quality" multichannel format, so even if CD quality is "as good as we can hear", DD may well have audible imperfections.


Link to Dolby Laboratories technical documents library (great source of information about all Dolby formats past and present): http://dolby.com/resources/tech_library/index.cfm
 

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Quote:
Originally Posted by Sonic icons /forum/post/0


DVD-Audio: 24bit/96kHz 5.1 channel PCM

DVD-Audio: 24bit/192kHz 2 channel PCM

Dolby Digital, 5.1 channel

CD: 16bit/44.1kHz 2 channel PCM (on the flip side of the dual disk)

The case on my Rhino Dual Disc "American Beauty" says the DVD-A stereo mix is 192kHz/24 bit resolution. But, both of my players (Denon 2900 and Panasonic S97) say the 2 channel track is only 96/24. Has anyone found a disc with the full 192kHz track?
 

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Quote:
Originally Posted by BIslander /forum/post/0


The case on my Rhino Dual Disc "American Beauty" says the DVD-A stereo mix is 192kHz/24 bit resolution. But, both of my players (Denon 2900 and Panasonic S97) say the 2 channel track is only 96/24. Has anyone found a disc with the full 192kHz track?

Maybe only the original DVD-A has the 192KHz tracks, and for DualDisc they had to scale it back to fit............................?
 

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Discussion Starter · #5 ·

Quote:
Originally Posted by oblio98 /forum/post/0


Maybe only the original DVD-A has the 192KHz tracks, and for DualDisc they had to scale it back to fit............................?

Very likely, because the DVD layer on a Dualdisc can hold only about half as many bits as the two layers on a "pure" DVD-A. (see for example "technical details" in this Wikipedia article on DualDisc)

http://en.wikipedia.org/wiki/Dual_disc
 

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Discussion Starter · #7 ·
The case and booklet (in the DualDisc release) show "Advanced Resolution 96kHz/24-bit surround, Advanced Resolution 192kHz/24 bit stereo". It seems odd that the producers of the disc would tell us that, if none of the releases (either original DVD-A or later DualDisc) actually had 192kHz/24 bit stereo.


(BTW, I'm skeptical of audible improvement from ultra-high PCM sampling rates, but for some reason I get interested in technical details like "is the stereo layer 192 kHz or 96 kHz" when people start to discuss it.)
 
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