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Uncompressed Digital Video vs. Uncompressed Digital Audio

Discussion in 'Electronic Basics' started by Radium, Feb 12, 2007.

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  1. Don Pearce

    Don Pearce Guest

    No problem - just buy one of these.

    http://www.codexdigital.com/

    d
     
  2. Gene

    Gene Guest

    Interesting little box, bet there are some really mean
    little DSP(s) inside... probably not 386 code...

    ************* cut-n-paste**************
    Can the DiskPacks simply be connected to another computer to access the
    data?
    The Codex DiskPacks feature proprietary hardware connectors designed for
    thousands of connect/disconnect cycles and this precludes them from simply
    being connected to any other computer to access this original data.
    Moreover, the material on the DiskPacks is not stored in an
    industry-standard format (such as DPX frames) but in the camera source's
    native output - conversions to DPX, QuickTime, HD video, AVI etc. are done
    only when the material is accessed in a Codex system.

    Gene
     
  3. Arny Krueger

    Arny Krueger Guest

    I think I saw something about 20,000 Pounds. I think that was currency, not
    weight - right? ;-)
     
  4. Norbert Hahn

    Norbert Hahn Guest

    Have a look at http://en.wikipedia.org/wiki/CCIR_601

    This is closest to raw digital video.

    Norbert
     
  5. CCIR 601 appears to be 4:2:2 That means that the
    chrominance data is compressed 2:1 (Like analog NTSC
    is).

    Of course DV is compressed 4:1:1 (NTSC) or 4:2:0 (PAL)
     
  6. Ron N.

    Ron N. Guest

    Only if you regard reducing the sample rate as a
    form of compression. But then your typical 44.1kHz
    audio CD has also likely been reduced in sample rate
    from 48 or 96 kHz as recorded in the studio. Is
    that compression? Or just an appropriate choice
    of filtering and data format?

    The chrominance in 601 is reduced to a bandwidth
    that better matches the typical human perceptual
    bandwidth of the luminance channel.


    IMHO. YMMV.
     
  7. If it weren't compression, they wouldn't bother doing it.
    Many would say "yes".
    Selecting a sample rate always performs some sort of
    "compression". One could argue that setting the sample
    rate of audio merely selects what you want your HF
    cutoff to be.

    OTOH, purposely digitally sub-sampling (or analog band-
    width-limiting) the color part of the image is a data-saving
    perceptual shell game similar to the lossy compression
    done by MP3, AAC, Ogg, et.al.
    And yet the casual observer can tell the difference
    between full-bandwidth RGB and reduced-color rez
    video transmission schemes when viewed side-by-
    side.
     
  8. Ron N. wrote:

    (snip)
    There was a story in Popular Science many years ago that I
    still remember about storing fast scan (normal TV) video
    on 0.25 inch audio tape. It ran the tape at 120in/s,
    with the cover page of the story showing the results after
    the tape breaks. They heat the record/play head to reduce
    friction. 10 inch tape reels were normally used to get a
    reasonable time. I don't believe it ever got popular.

    -- glen
     
  9. When I was a kid, I was trying to record the video signal from TV to a
    modified conventional cassette tape recorder. For that purpose, the
    recorder was operating in the fast forward mode, so the tape speed was
    about 2m/s. I was able to establish the horizontal and vertical sync,and
    even to see something, however I woudn't call this a picture.

    Vladimir Vassilevsky

    DSP and Mixed Signal Design Consultant

    http://www.abvolt.com
     
  10. I used to use 2" wide (so far more robust) instrumentation tape at 120
    inches/second. The drives used air bearing guides, to reduce friction,
    but dragged the tape across ordinary heads with no special method of
    dealing with heat or friction. They did have elaborate arrangements to
    stabilise the tape as it passed over the heads, though. A 15" reel of
    tape ran for about 16 minutes, and had 24 or 28 tracks. Those drives
    used to be the mainstay of instrumentation in a number of fields (mostly
    military). They could put a fair quality TV picture onto each of their
    24 tracks. Several people made drives of that kind - Ampex, Honeywell,
    Enertec, and others. We used to fly compact versions, while large floor
    standing ones were used in the lab.

    So, the popular science article was not describing anything crazy. I
    just wonder about handling 0.25" tape at that speed.

    Regards,
    Steve
     
  11. Mr.T

    Mr.T Guest

    Not at all. Compression involves a manipulation of data *within* the range
    under consideration. (either lossy compression or lossless)
    If extraneous data falls completely outside the required range, then no
    compression is necessary within that range.
    No, there would be no *real* argument at all, since that *is* what it does.

    MrT.
     

  12. And limiting the bandwidth is a form of "data compression".
    It was invented before our grandparents were born in
    the days of early telephony.
     
  13. Jerry Avins

    Jerry Avins Guest

    Richard Crowley wrote:

    ...
    Call it data reduction if you wish. "Compression" is generally given a
    more restricted meaning.

    Jerry
     

  14. That is also the definition of "Creative recycling". :)


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  15. Mr.T

    Mr.T Guest

    No, you are simply misusing the term "compression".
    By your definition *everything* that does not include DC-infinity (ie.
    everything full stop) is therefore "compressed".
    Good luck with getting that generally accepted as a new definition.

    MrT.
     
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