Audio-encoding question.

Discussion in 'Archived Threads 2001-2004' started by Garrett Lundy, Mar 11, 2002.

  1. Garrett Lundy

    Garrett Lundy Producer

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    Just to satisfy my own curiosity (It's driving me nuts).

    The range of human hearing, on average, is said to be from 20 to 20,000 hertz. Assuming this is true, I was wondering....

    * Is AC-3 (from laserdisc) capable of 20-20k? I'm assuming it is because LD technology was taken from the CD technology which had a 20-20k range. But I'm not sure on this.

    If DTS has a higher sampling rate than DD....

    * What are the maximum sampling rates of CD's, AC-3 LD's, Dolby Digital DVD's, DTS DVD's, SACD's, and DVD-A disks?

    * Do DTS-ES, and THX-EX encoded DVD's have a larger sampling rate than their more mundane counterparts?

    Again, This is simply a topic that I'm curious about. Although in future it may be important when I decide to buy some new HT equipment.And thanks in advance for all the useful info!
     
  2. Vince Maskeeper

    Vince Maskeeper Producer

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    Garrett,
    You have actually asked a more complicated question than you realized...
    Nope- but I think you're confusing "sampling rate" for "data rate". Each channel is still sampled at the same rate digitally speaking- and then compressed. The 6.1 formats don't have a larger final encoded size either.
    Since DD EX is simply matrixed, it simply has 2 rear channels which an analog processor can "extract" a rear center channel.
    DTS "discrete" 6.1 ES has an extra channel in the datastream-- but the same maximum data rate for the format is in place- so that "extra channel" has to pull the bits for its audio from the same overall data rate as 5.1 is given.
    -Vince
     
  3. Bob McElfresh

    Bob McElfresh Producer

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    Hi Garrett.

    I'm afraid there is a concept problem here.

    There is no SAMPLING RATE for AC3/DVD. It's not a encoding/sampling spec.

    AC3 is a compression routine. It takes already sampled data and compresses it 6 to 1.

    I'm not as familare with DTS, but I believe nobody records in DTS, it's also a compression routine with less loss.

    I believe both of these are optimized for 16 bit, 48 khz sampling - the CD standard.
     
  4. Vince Maskeeper

    Vince Maskeeper Producer

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    Not to step on Bob's toes, but...

     
  5. Bob McElfresh

    Bob McElfresh Producer

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    Corrections always welcome Vince [​IMG]
    I did a lot of work with AC2 compression from Dolby. At that time it was a perfect 6:1 compression. A 60 second stereo radio commercial would take about 12 megs uncompressed PCM. Using the AC2 encoded cards, the files were 2 megs.
    I was assuming they fixed the few problems found, but kept the same routines, but blew it out to 6 channels. But it wouldnt be the first time I was wrong.
     
  6. Adam Barratt

    Adam Barratt Cinematographer

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    Real Name:
    Adam
    Just to add a few numbers:
     
  7. Garrett Lundy

    Garrett Lundy Producer

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    Hey! Thanks for the info. My brain can now rest easier knowing that it will probably never, ever comprehend half of this stuff. Or maybe it will...Bah! I'm still trying to figure out the meaning to the ending of A.I., I'll have to save all this math for tomorrow.

    But now I'm glad I only asked about the audio part of home theater..I wonder what differant video formats use for digital information when sent to a display......(Be warned, answer this question and I'll probably just ask another one)
     

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