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Uncompressed PCM Video

Discussion in 'General Electronics' started by Radium, Sep 10, 2003.

  1. Radium

    Radium Guest

    Why aren't there any PCM video devices?

    I have seen countless PCM audio devices. Why not use the same for
    video?

    Just give it a strong bit-resolution, a low frequency sample rate, and
    multiple video channels and you will get quality much better than MPEG
    video.

    MPEG is data reduction and looks bad on the screen. It may work for 2D
    video but not for 3D video.

    I would like to use strong bit-resolution, slow sample rate, multiple
    channels PCM video for virtual reality.
     
  2. Because PCM video has the same issues as PCM audio, the main one
    being that high data rates are required.
    Oh I see, by low frequency, you mean a few frames per second. Each
    frame still has to be captured quickly, but that's simple.
    I'd imagine there are such things for applications such as
    security and surveillance. But for VR? In my mind, and I think to
    many others, high frame rate is MORE important than image quality,
    especially for moving images. The human eye has a lot of motion blur,
    so there's no point in showing a lot of detail over the whole frame
    if your head is spinning.

    I'd rather have 30fps cartoons in my VR world than 5fps photographs,
    unless I'm doing something like very methodical environment exploration.

    Let us know what you find.
     
  3. Radium

    Radium Guest

    Well I was thinking about designing psychedelic VR equipment. My
    theoretical design is not for movies or stories but for VR effects
    with different patterns of colors and images to entertain the visual
    cortex. There is no audio and none needed. Multi-channel video would
    intrigue the mind more than one-channel video. The slow sample rate
    would add to the mystical vertigo. Video with stronger bit-resolution
    is more appealing to the eyes than video with weaker bit-resolution.

    The artifacts affecting MPEG video are imperceptible on a
    television/computer monitor. In VR, however, they would be a real
    annoyance. That is why I prefer to use PCM video. My theoretical PCM
    video is stored on a laser disc.
     
  4. Gary Tait

    Gary Tait Guest

    Becuase it would terribly hog bandwidth or storage.
     
  5. You do realize that Laserdisc *is* analog video, don't you?

    Obviously, the limiting factor is data rates. You get a lot more storage on
    DVD than you would on laserdisc.

    Next stop...Blu-Ray. That will give us much more storage for higher quality
    video...coming soon!

    Speaking of which, it annoys me to no end to see tv reporters use video
    phones where they crank up the frame rate and the image quality is crap. In
    a 30 second report, they could deliver 10 really great images, but instead
    choose to send 500 images that are all one big fuzzy mess. I don't
    understand why they don't pre-load a slideshow of high quality images before
    the broadcast and then during the broadcast just do high quality audio,
    letting the studio mix the audio with the pre-sent images. If it is
    something happening *live* then it makes sense to do both at the same time,
    but lower the frigggin frame rates!
     
  6. Bob May

    Bob May Guest

    Actually, a lower frame rate just makes for a jumpy video. You do want the
    minimal speed of 30FPS to integrate the images into a smoothly moving stream
    in the brain. There is a reason whey the major video transport systems were
    built on interlaced scanning and it wasn't to make things simple. The high
    speed of the construction of the image at 60 or 50 FPS helps in making the
    images blur into a continous stream rather than a number of photos.
    I'll also note that the input/output of the MPEG stream is indeed PCM video
    and it is simple math to figure out the bit rate that is needed to
    accomplish the result, something that I'll leave to your calculating.
    MPEG can be adjusted to produce a higher basic data stream or a lower,
    depending upon the desired quality but for a local application, it is a
    layer that is really not needed. Anybody transporting video data over a
    short link is really wasting money converting it to a MPEG stream.
    BTW, can you tell me where you have seen MPEG artifacts in any video? Do
    you see it in movies or other stuff on TV? Do you see it in Satellite TV?
     
  7. Samuel Paik

    Samuel Paik Guest

    If you mean, video codecs that support raw video, then almost all
    the cheap devices do (well, technically the hardware only supports
    4:2:2 YCrCb video)
     
  8. Radium

    Radium Guest

    Yes, however, my design of it isn't. What I meant by "laserdisc" is a
    disc of the same size and shape of those commercial laserdiscs. The
    signals stored on mine are digital PCM.
    My design of laserdiscs uses long-wave UV lasers (black light) to burn
    pits into the disc. Commercial ones use infrared lasers. Since UV is
    of a shorter wavelength than IR, I can store more pits of info on my
    discs than the commercial discs.

    Also since laserdiscs are bigger than DVDs, they store more data.

    I agree.

    The solution is strong bit-resolution and slow sample frequency.
    Driving up the frame rate can make a painful eyesore out of any
    original video.

    For an aural equivalent try encoding digital audio at 2 KHz. After
    recording increase the sample rate of the file to 44.1 KHz. Scrathy
    high-pitched hiss will give you a migraine.
     
  9. You can throw out all the "seemingly correct and aweinspiring"
    terminology, and obviously many "will bite the bait", but methings
    you've snorted WAY WAY too much of that multicolored, psychedelic "pixie
    dust."

    Either that or you're having one hell of a laugh at the expense of what
    appears to be an endless supply of hapless fools.

    OK, you made me chuckle, so maybe it's worth it.....:)
     
  10. luminos

    luminos Guest

    Total and complete idiocy. See Roederer: Introduction to the Physics and
    Psychophysics of Music, 3rd edition, Springer Verlag.
     
  11. Skywise

    Skywise Guest

    I see it all the time on my Direct TV system, and I'm not talking about
    the occasional glitching caused by loss of data. I see it mostly in
    areas of the image that are mostly the same color, like say a background
    wall. Also, video-text has what I call 'jaggies' all around it, just
    like in a computer jpeg image of low quality. And no, I dont' have a
    high res TV...just your garden variety cheap 28 incher.

    I've thought of sending them an email saying that considering I'm
    paying $xx for their service and they advertise 'digital quality' that
    I should expect a better picture. They're obviously over compressing
    their signal.

    Most of the time it's not obvious, but there are times when it just
    jumps out at me.

    Brian
     
  12. There is uncompressed PCM for video. The data rate is 270 Mbit/sec for
    standard definition, 525 line, 60 field interlaced. The computer folks
    refer to this as 480i. For Hi def, the data rate bumps up to 1.5
    Gbit/sec for 1920x1080 interlaced. Looks danged fine,too. This stuff
    is only seen in studios and post production facilities. It makes going
    to work fun.

    GG
     
  13. Bob May

    Bob May Guest

    Brian, digital TV is like digital audio. The frequency response is horrible
    but the rendition is wonderful for the most part and you can copy it forever
    without loss of that quality.
    Depending upon the level of compression, the artifacts may show up and at
    the higher compression levels the thing to look for is blocks )basic
    luminance block is 8x8 and a color block is 8x16) of a solid color (best
    seen with a slowly varying color or shade due to shadows) over a surface.
    With MPEG, fast motion can produce some blocks Reduce the level of
    compression and the artifacts become a lot scarcer.
    Audio has the same problems in that the basic highest reproducable frequency
    with the basic digiatal audio is in the range of about 15KHz and the earlier
    tape and vinyl was able to reproduce that high stuff a lot better. It does
    have the ability to be a quieter medium tho if the processing of the audio
    is done properly before being converted to digital.
     
  14. Radium

    Radium Guest

    What medium is it stored in?
    Do they have any video PCM file formats?
    Any of these studios make visual psychedelic virtual reality with PCM video?
     
  15. Ian Stirling

    Ian Stirling Guest

    You don't typically store these on hard disks, they are too big.
    At 270Mbit/sec, you can only store an hours video on a 120G disk.
    At 1920*1080, you need several disks just to cope with the bandwidth.
    5 120G disks will just about cope with an hour.

    --
    http://inquisitor.i.am/ | mailto: | Ian Stirling.
    ---------------------------+-------------------------+--------------------------
    "Melchett : Unhappily Blackadder, the Lord High Executioner is dead
    Blackadder : Oh woe! Murdered of course.
    Melchett : No, oddly enough no. They usually are but this one just got
    careless one night and signed his name on the wrong dotted line.
    They came for him while he slept." - Blackadder II
     
  16. Ian Stirling

    Ian Stirling Guest

    Digital with decent bitrates beats 99% of analog systems, and uses less
    bandwidth.
    Then the accountants get to it and decide that you don't want picture quality,
    you want hundreds of channels in the space where ten should really be
    put.

    This is the reason that the latest DAB digital radio currently rolling out
    over the last bits of the UK is lower quality than a FM signal.
     
  17. Radium

    Radium Guest


    But these are for movies. Movies usually have a long story and thus
    need a lot of storage space.

    Would psychedelic patterns of different images and colors in virtual
    reality require a similar amount of storage space? Minus the audio
    because my design doesn't contain any.

    In addition, an optical disc can store more information in the same
    distance than a magnetic disc of the same size.
     
  18. Ian Stirling

    Ian Stirling Guest

    Why would you need to store them as PCM?
    Not with commonly available technology.
    DVDs get around 5Gb/disk, which is around 1.6 times the area of a hard
    drive platter.
    I haven't looked inside my 120Gb drive, but there is no way there are 36
    platters in there.
     
  19. luminos

    luminos Guest

    Because this guy knows nothing and needs to study more carefully.
     
  20. Bob May

    Bob May Guest

    Methinks that you should really just sit down and look at the things that
    you are talking about rather than arguing about it with people that know
    exactly what you are talking about. These problems have all been worked
    over in many different ways - every few decades, the technology gets a major
    revamping due to better abilities in recording and storing data. Who knows
    when the generation of video in the digital domain will change but some are
    already calling for changes. Are you ready for 12 bit video? That will
    increase the raw stream by 50% and make all of the present day encoding
    schemes obselete.
     
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