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Bitrates (for the techies)

Discussion in 'Movie Forum' started by Simon6776, Jul 29, 2004.

  1. Simon6776

    Simon6776
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    I've read a lot on this forum "Cor.. it's got full bitrate DTS, and that other one only had half bitrate..." Well, can somone explain, simply, the difference, please? On an average home system, at a 'normal' volume, is there any real discernable difference with half and full bitrates?
     
  2. BrianC

    BrianC
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    The dolby digital and DTS formats are lossy - in other words they compress the size of the orginal recording by dropping parts of the recording. How much gets dropped is dependant on the encoding method, and bit rate.

    On paper a higher bit rate should result in more information being encoded; its certainly noticable for MP3s between 128 kbs and 192 kbs on even an average HT setup - the sound is more expansive. Hi hats are the biggest thing for me - they never seem to encode properly for MP3.

    In the real world, its dependant on your HT setup, the orgnial source (crap in - crap out), and the quality of the encoding. A good test would be the half rate Western releases vs the full rate Japanese disks in a blind test, assuming they are from the same, quality, master.
     
  3. Reiner

    Reiner
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    Actually bitrate is not an absolute measure for sound quality, in particular not if you compare different formats like DD and DTS as then the efficiency of the encoder would define the bitrate.

    Therefore the same master encoded in format A, at a low bitrate, can sound the same or even better than format B that has a higher bitrate (but a less efficient encoder).
    Of course it is also possible that the lower bitrate encoding is inferior to the higher one.

    I doubt that most people could tell the difference between half and full bitrate DTS, given they don't know which one they are listening to.
     
  4. Steve.EX

    Steve.EX
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    Agreed, and then we are back to the old argument as to can you tell between what is actually better and what is merely different.
     
  5. Simon6776

    Simon6776
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    My reason for asking this is that I've seen two different DTS versions of Total Recall. Apparently the Jap version is 'full' bitrate, whereas the cheaper Korean version is 'half' bitrate, and supposedly sounds inferior to the DD5.1 mix.
     
  6. BrianC

    BrianC
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    if its true (i've only the US copy so I can't compare, and I doubt my kit is good enough to really tell anyway) then it could be down to the encoding or to the master used.

    Really DTS should equal DD in terms of quality, if the DD is better that suggests to me that either a different master or mix of the master was used, or poor encoding of the same master into DTS occured.
     
  7. Reiner

    Reiner
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    As you don't know if both have been derived from the same master or how much care has been taken during the mastering/encoding process I am not sure you can attribute any difference to the bitrate only.

    My advise: buy the DVD with the soundtrack that sounds better (or, if you trust other, which is said to be better), regardless of format and/or bitrate.
     
  8. Simon6776

    Simon6776
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    Well, it says on DVD Compare that the Korean DTS is significantly inferior to the DD5.1 soundtrack, so I guess that answers the question.
     
  9. FoxyMulder

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    Fullbitrate DTS is supposed to have an upper frequency response all the way to 24Khz and the halfbitrate version claims 19Khz but it drops badly after 15Khz ( so some claim ) our ears are supposed to pick up frequencies up to 20Khz although as we get older this dimishes rapidly, so i suppose FullBitrate DTS can be said to be superior because of the better frequency response and not because of the actual bitrate although thats the reason the frequency can go all the way to 24Khz ( but do films make advantage of this full frequency is what you should ask yourself and the answer is some do and some don't )
     
  10. Reiner

    Reiner
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    If Dolby, which uses an even lesser rate than half-rate DTS, does not roll-off after 15kHz but instead goes to 20kHz (which is said to be the upper limit of the human hearing), than it would mean DD is better than half-rate DTS.

    Just provoking some thoughts, not saying A or B is better. :)
     
  11. BrianC

    BrianC
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    so what is dolby digital dropping from the audio? it has to be dropping something...
     
  12. Reiner

    Reiner
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    Of course it does - but so does DTS. The difference lies in the encoding algorithm.

    You probably can find some more info here: Dolby Technologies
     

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