LD PCM vs. DVD audio quality comparison

Discussion in 'DVD' started by BrianBo, Jun 25, 2005.

  1. BrianBo

    BrianBo Stunt Coordinator

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    My priority when watching movies on my HT is definitely sound quality.

    Some of the PCM tracks on LD that I would like opinions on are Falling Down, Heat, Commando, The Game, Seven, Miller's Crossing, etc.

    I would also like some recommendations on other LD PCM tracks that smoke their DVD counterpart.
     
  2. Grant B

    Grant B Producer

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    Early On; I had Stargate both on DVD & LD. Even though the AC3 LD should have been the same as the DVD.....it wasn't. Switching between the 2; the LD won by a landslide
     
  3. Kevin M

    Kevin M Producer

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    Kind of a moot point IMO (LD-PCM having better over all SQ while 5.1 formats have a much wider soundstage, and LD being dead as disco)....however one of my favorite LD PCM tracks is on Criterion's 1993 title This Is Spinal Tap, the film's music tracks have a higher fidelity than even the CD/LP did, a robust track.
     
  4. Jeff_HR

    Jeff_HR Producer

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    As along as people still play LDs & purchase them from places like eBay, they are not DEAD!
     
  5. Kevin M

    Kevin M Producer

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    (shrugs shoulders) I love my LD collection but as a produced and evolving format...it is dead, sorry.
     
  6. Tom Brennan

    Tom Brennan Screenwriter

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    It's really not dead, as long as we remember it.
     
  7. Kevin M

    Kevin M Producer

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    Not at all, I'm just saying that IMO it is moot because newer formats evolve, this one won't, it is dead from a product point of view. From a user POV...I have 73 LD's and I actually watch quite a few of them from time to time so it isn't dead from that standpoint but as a format that can compete with newer video/audio formats it is out of the game.

    But for this thread's topic it still can compete in one way with today's DVD standards, IMO the PCM tracks on the first releases of Jurassic Park (for example) are still WAY above the DTS & DD 5.1 tracks in pure gusto, the bass in the PCM tracks is a real gut buster compared to it's 5.1 counterparts...then again I have always wished for more PCM tracks on DVD titles. The argument against it being one of bit space on a DVD...that didn't stop The Wall from having a very good PCM track AND fairly good PQ plus quite a few extras...just imagine what Two discs could offer. That's an argument for another thread...or is it connected?
     
  8. Steve Tannehill

    Steve Tannehill Ambassador

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    The DTS track from Jurassic Park on LD tripped the breaker on a 15-amp dedicated line in my home theater. Ouch!

    - Steve
     
  9. Kevin M

    Kevin M Producer

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    I was talking about the DVD's DTS track, the LD's DTS track is a hyper sweetened bass heavy monster as well but I still didn't think it was as robust as the PCM track.
     
  10. Ken_McAlinden

    Ken_McAlinden Producer
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    I think the Miller's Crossing LD PCM track is superior to the DVD 4.0 track. The DVD sounds like some dynamic range compression was applied compared to the pro-logic track. I like the LD PCM track on Beauty and the Beast better than the DD5.1 remix on the DVD, mostly due to musical fidelity. The same goes for The Lion King and The Little Mermaid, although in the case of The Lion King, I'm only talking about the original theatrical mix, not the Disney Enhanced Home Theater mix, which is a lot more active and is a fun listen on the DVD.

    With The Lion King and The Little Mermaid, I even like the PCM tracks more than the 5.1 tracks on the laserdiscs themeselves.

    Regards,
     
  11. MikeEckman

    MikeEckman Screenwriter

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    I just dont understand why Dolby 2.0 tracks on DVDs cant be as good as their PCM counterparts.

    I can take an audio CD and rip it to my computer in PCM format, and then compress that data to a 192kbit MP3 and keep the sound almost identical. What barely audible differences there are between a 192kbit MP3 and an original PCM audio track isnt anywhere near the huge differences between LD PCM tracks and corresponding Dolby 2.0 tracks on DVD.

    Can anyone explan what the difference is?
     
  12. ChristopherDAC

    ChristopherDAC Producer

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    Well, firstly, I'm guessing that you don't play your MP3s at the incredibly loud "reference level" some people maintain in their home theatres. That really does make a difference in terms of detecting compression artefacts. Secondly, if you are listening to most popular music produced today, its dynamic range has been severely restricted in the mixing process to make it sound "hot", which makes things much easier on the compression algorithm. Motion-picture soundtracks, on the other hand, frequently have quite a bit of dynamic range, so if "reference level" were not set so high there would be some difficulty hearing quiet sounds. Thirdly, if the audio was originally mixed in Dolby Stereo Surround, there are phase-shifts and other information embedded in the audio stream for the decoder [your Pro-Logic reciever, typically] to rebuild the 4.0 channel mix from; the various clever techniques which AC-3 [the Dolby Digital codec used on DVDs and to an extent LDs] uses to keep down the bitrate can play hob with these cues, particularly its trick of mixing together the high frequencies under certain circumstances. 2.0 channel AC-3 at 384 kbps, the typical bitrate for 5.1, should be indistinguishable in practice from PCM, but it is rarely used.
     
  13. Simon Howson

    Simon Howson Screenwriter

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    I thought hot mastered audio was harder to compress, and achieve transperancy. For example I back up a lot of CDs using FLAC and to LAME MP3. My classical and jazz CDs compress a lot better than a newly made rock music CD. I'm lucky if I get 25% file reduction on a recent rock music CD, where as 35% - 45% is the norm for classical and jazz.

    For MP3 most of my classical CDs average around 165 Kbps VBR, but a modern rock CD usually always hits 200 Kbps VBR, some of my rock CDs are 250 Kbps VBR. These encodes are with LAME --preset standard.

    Sure Dolby psycho accoustic models could be better tuned. But in terms of music, lots of dynamic range compression usually means the music won't compress in data terms very well.
     
  14. ChristopherDAC

    ChristopherDAC Producer

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    Virtually all audio compression technologies are founded on DPCM. They may divide the audio into frequency bands, and apply psychoacoustic masking, and all the rest, but somewhere along the line they are taking the difference between one sample and the next. If the samples are within a more restricted range of amplitudes, that will mean that the mantissas can be shorter and the exponents changed less frequently. What you are seeing with MP3s is probably a result of the various frequency bands being roughly the same amplitude, which messes up the basic MPEG [audio as well as video] approach of coarsely quantizing or throwing away frequency components of a smaller magnitude. I suspect that if you try messing with the encoder settings you may find one which encodes rock at a smaller size than classical; maybe not, depending where in the encoding chain the differentiating step falls [I don't have the details at my fingertips].
     
  15. Ken_McAlinden

    Ken_McAlinden Producer
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    I'm pretty sure that DPCM is used as an acronym for "Delta Pulse Code Modulation", which is not what I think you meant. Most stuff in the audio realm is based on linear pulse code modulation (LPCM) to the extent that if the acronym PCM is used by itself, that's normally what is meant.

    Regards,
     
  16. ChristopherDAC

    ChristopherDAC Producer

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    They take in LPCM, and take the difference between adjacent samples [most systems actually include a simple "predictive" element instead of simply looping back the last sample, but that's another story] -- Differential [or Delta] PCM. Then, usually, a process called "companding" generates a "range" or "exponent" value which indicates the dynamic range of the signal, and a "mantissa" which indicates a specific value within that range -- Adaptive DPCM. The simplest systems [DANCE, NICAM, AC-1] stop there, while more complex ones [MPGA, dts, AC-2, AC-3, MUSICAM] have a variety of other processing steps which may come before or after the ADPCM step.
     
  17. Ken_McAlinden

    Ken_McAlinden Producer
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    When I was studying signal processing, delta PCM was using integers to represent the differnce between current and previous samples. I knew that most of the codecs use floating point representations with dynamic bit allocation for exponents and mantissas for samples, but I was not aware that they were encoding differences rather than absolute values. In any case, using floating point representations for audio signals makes sense when one considers the ear's logarithmic response to changes in levels.

    Regards,
     
  18. MikeEckman

    MikeEckman Screenwriter

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    Wow! Chris, your response made a lot of sense to me. [​IMG] Thanks for taking the time to write it.
     
  19. Kevin M

    Kevin M Producer

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    Indeed, when it is used it sounds damn good, Anchor Bay's original Night Stalker used this BR and the difference between that title & MGM's re-release at 196 is noticeable, Image's Mystery Science Theater 3000: The Movie also uses that bit-rate and it sounds remarkably close to the LD's PCM tracks...I don't know about identical but pretty close.
     
  20. DaViD Boulet

    DaViD Boulet Lead Actor

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    Agreed! I've said that over and over...why not just give the 384 kbps usually used for 5.1 to the 2.0 mix...that would sound AMAZING. I've heard Dolby Digital on D-VHS which uses a much higher rate than DVD (about twice I think) and it sounds BETTER THAN DTS ON DVD!!!!!! Giving all that room to a 2.0 track could give you a 2.0 mix that sounds better than a 5.1 mix at the same rate in some cases I have no doubt!
     

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