DTS in the theater vs. DTS on DVD

Discussion in 'Archived Threads 2001-2004' started by MarkHastings, Mar 3, 2003.

  1. MarkHastings

    MarkHastings Executive Producer

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    When we talk about DTS on a DVD, are we talking about the exact same thing as DTS in the movie theater?

    I understand that DTS is more discreet (which makes sense in the movie theater concept), but what about the fact that DTS DVD's use less compression (compared to DD5.1)? Is there any relevance to the compression schemes in theatrical presentations? If not, how does the compression relate to DTS on a DVD?
     
  2. Michael Reuben

    Michael Reuben Studio Mogul

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  3. kurt_fire

    kurt_fire Stunt Coordinator

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    no, dd uses a lower bitrate than dts. my preference is dts, but dd sound darn good too.
     
  4. MarkHastings

    MarkHastings Executive Producer

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  5. Michael Reuben

    Michael Reuben Studio Mogul

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  6. MarkHastings

    MarkHastings Executive Producer

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    Thanks for the link Michael...I didn't download that PDF when I was on DTS's site before.

    So it sounds like Full bit DTS DVD's are a slightly higher bitrate than DTS in the theater.

    Cool.
     
  7. Michael Reuben

    Michael Reuben Studio Mogul

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  8. MarkHastings

    MarkHastings Executive Producer

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    Maybe I'm missing something here, but exactly how is theater DTS compression different from DVD DTS?

    From the DTS pdf, it says that DTS (for theaters) is put onto a CD with a bit rate of 1.4Mb/sec at 44kHz, whereas the DTS on a DVD can run 1.5Mb/sec at 48kHz. To me, it sounds like the DVD DTS should be slightly higher quality because the data rates are higher.

    I realize what you mean that data rates are meaningless if compressed differently, but I would think the difference in DTS DVD's and DTS theater would be somewhat similar? The theaters use CD's and DVD's use (obviously) DVD's. They're both optical mediums...can you explain what the difference in compressions is?
     
  9. Michael Reuben

    Michael Reuben Studio Mogul

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    I'm not sure where you're getting those figures from.

    According to the DTS article I linked to, theatrical DTS runs at 882kbps using a codec known as apt-X100. And it doesn't use CD; it uses CD-ROM.

    Home DTS is based on a different codec ("coherent accoustics") and runs at 1.235Mbps on CD and LD and 1.509MBps or 754kpbs on DVD.

    The 1.4Mbps figure is the available bandwidth on CD.

    I don't claim to be an expert in the technical details of compression techniques, so someone else will have to explain the precise differences between the codecs. (Paging Adam Barratt!)

    M.
     
  10. Adam Barratt

    Adam Barratt Cinematographer

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    I think you're pretty much covered it, Michael.

    DTS in theaters uses the APT-X100 compression scheme, which uses a compression ratio of roughly 4:1 and is limited to 16-bit resolution in its current configuration.

    DTS in the home uses the Coherent Acoustics system, which is extremely flexible with bit-rates of 32kbps to 4096kbps and typical compression ratios of around 3:1 and up.

    The theatrical APT-X100 system uses a well-worn technology called ADPCM to compress audio. This process is very nearly lossless. That is, what comes out of the decoder is almost identical to what goes into the encoder. Space is saved by eliminating unnecessary (redundant) data and by using a mathematical model that 'guesses' what the next piece of data will be.

    Coherent Acoustics is a much newer system that utilises most of the systems used by the theatrical system, but with much greater precision. It also adds 'psychoacoustic' modeling to the mix, a system that the theatrical format does not use.

    Psychoacoustic modeling determines what information can be discarded from the encoded audio without making an audible difference. For example, louder sounds generally mask quieter sounds so discarding the quieter sound won't make any difference to the listener, but allows less data to be used. The combination of this newer system's greater precision and psychoacoustics allows domestic DTS to compress audio more than the theatrical system without any loss in audio quality. It can, in fact, produce much higher audio quality than the theatrical system at much lower bit-rates.

    As you can see, even though the compression ratios and bit-rates can be similar, the way the information is compressed is different, and the fidelity of the end product can vary at similar bit-rates. For example, at 882kbps DTS in theatres offers five channels of 16-bit audio. At a lower bit-rate (754kbps) the domestic version on DVD allows up to six channels of 24-bit audio.

    However, as Michael has already pointed out, because the two systems are completely different, there's not much point directly comparing them at the same bit-rates.

    In terms of absolute fidelity, the domestic system is capable of much higher resolution and much greater frequency response than the theatrical system.

    Adam
     
  11. MarkHastings

    MarkHastings Executive Producer

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    Thanks Adam, that's exactly what I was looking for.

    Michael, sorry if I posted confusing info. I posted the question on this forum because I find those white papers/techy PDF's to be somewhat overwhelming. I couldn't seem to nail down the exact info I was looking for in it, but you and Adam explained it better than what my research uncovered.

    thanks again
     

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