HELP: First attempt at DV capture - corrupt signal

Discussion in 'Video Cameras' started by H Bergeron, Aug 25, 2004.

  1. H Bergeron

    H Bergeron Guest

    Hi, I'm a newbie. I've just installed my firewire card and had my
    first go at DV capture from my Canon MV700i

    It worked - sort of. But there are "glitches" on the captured footage:
    bursts of noise on the audio and flashing squares of colour on the
    screen. Neither of these is in evidence when I view the tape on the
    camera.

    I get the same problem whether I capture with Ulead Videostudio 7 or
    Pinnacle 9, so it would seem to be a hardware problem.

    But the thing is, the problem is more severe on some parts of the
    original tape than others (it's especially bad at the start), and the
    patterns/noises crop up predictably, e.g. 4 secs from the start of the
    tape there is a big blip followed by a persistent trail of
    random-looking squares down the centre of the picture - repeatably for
    several attempts at capture.

    So the hardware outside the camera (cable, firewire card, PC) isn't
    just producing random corruption; something about what the camera is
    reading from the tape is at least contributing.

    Any ideas?
     
    H Bergeron, Aug 25, 2004
    #1
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  2. H Bergeron

    John Russell Guest

    Try just capturing the CCD output direct without using the tape mechanism.
    If that has problems then it isn't the tape.
     
    John Russell, Aug 25, 2004
    #2
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  3. H Bergeron

    H Bergeron Guest

    Thanks, just tried that and haven't been able to replicate the
    problem. So it would appear the tape is implicated. I'm off out to buy
    a more expensive tape.

    But why would the corruption not be visible/audible when played back
    on the camera itself?
     
    H Bergeron, Aug 25, 2004
    #3
  4. H Bergeron

    Jukka Aho Guest

    Better error correction / concealment inside the camcorder
    than in the DV codec implementation on your PC?

    For example, if the camcorder detects errors in the DV stream,
    it is technically possible to try and conceal them by repeating
    the picture (or parts of it) from a previous, known-good frame.
    Maybe the PC DV codec does not this but the codec inside the
    camcorder does?

    (Just a guess, I have not encountered anything similar.)
     
    Jukka Aho, Aug 25, 2004
    #4
  5. H Bergeron

    H Bergeron Guest

    Thanks for the response.

    I used End it All to shut down other programs.

    I have 512 Mb of memory. PC has an AMD Athlon 2200 MHz
    Been there, very helpful, thank you! I haven't yet followed the advice
    there about sorting the interrupt priorities of PCI devices. Don't
    know if it'll help my problem but definitely looks worth doing.

    OTOH I'm still mystified that the problem is linked to particular
    places on the tape (going away completely for capture of what the
    camera is shooting that moment, rather than tape playback) and yet the
    camera can play back a seemingly error-free signal to its own screen
    or to analogue TV input.

    Jukka Aho has posted about codecs, which is leading me well out of my
    depths. Is there any way of testing his theory, and if it's right, is
    the problem curable?

    Many thanks for your help already and in anticipation for any more you
    can offer!

    Cheers.
     
    H Bergeron, Aug 25, 2004
    #5
  6. H Bergeron

    H Bergeron Guest

    Thanks for the response!

    Is there any way I can test this theory, or correct the problem if the
    theory is correct?
     
    H Bergeron, Aug 25, 2004
    #6
  7. H Bergeron

    Matej Artac Guest

    It's odd that H Begeron reports no artifacts when he captures live video,
    i.e. not from the tape. He also says the artifacts seem to be
    tape-position-dependent. Do you think it is the control signal somehow
    messing up the picture?

    It may be a good idea to test the DV capture on another machine, like at
    friend's. This should really be a good diagnose whether the problem is on
    the cam side or on the computer side. Further, and this may be a bit of a
    wild idea, if the problem is driver-related, maybe he could try how it works
    in Linux - there are downloadable .iso files that make a bootable CD with
    the necessary drivers and software for DV capture.

    Matej
     
    Matej Artac, Aug 25, 2004
    #7
  8. H Bergeron

    mrlipring Guest

    sounds like you're just saying random things to me. It's nothing to do with
    the memory. Did you read the entire thread? it consistently happens with
    that tape, but not with straight-from-the-ccd capturing.
     
    mrlipring, Aug 25, 2004
    #8
  9. H Bergeron

    mrlipring Guest

    you're just making it up! You're pulling stuff outta your ass again. Jesus,
    you're incredible!
     
    mrlipring, Aug 25, 2004
    #9
  10. H Bergeron

    mrlipring Guest

    ok, we seem to be sure it's a problem with the tape, or your camera's
    tape-reading/decoding process, yes?

    the problem happens with capturing from the tape, but not straight from the
    ccd.

    Is it possible for you to experiment further?

    Can you:

    try a different tape? record onto a new tape, and try and capture the
    footage. Does it give the same errors?

    try capturing with a different camera? try the same tape (and other tapes if
    you like) with (a) different camera(s), to see whether it's possible a
    camera problem, or a tape problem.

    Try re-recording over the apparently affected portion of tape, to see if
    it's a problem with the tape itself, rather than the data recorded on it?

    I must admit that i don't know enough about the process of recording to a
    tape or reading from a tape to be able to say why it's happening, but at
    least this way we could ascertain *what* is happening.
     
    mrlipring, Aug 25, 2004
    #10
  11. H Bergeron

    H Bergeron Guest

    Thanks, will try that when I next get a chance to tinker - might be
    the weekend now.

    Will report back if I make any progress.
     
    H Bergeron, Aug 25, 2004
    #11
  12. H Bergeron

    H Bergeron Guest

    Done a few more trials. The "artifacts" are not utterly predictable to
    the frame, but their frequency and type do appear to depend on tape
    position. I am still unable to replicate on live video.
    Ideas gratefully noted. Will be a few days before I get the chance to
    try on another PC. Will report back here if I find any answers.

    Many many thanks for the input.
     
    H Bergeron, Aug 25, 2004
    #12
  13. H Bergeron

    H Bergeron Guest

    Bought a slightly higher quality tape (Sony Premium) and tried again.
    Got the same glitches, perhaps with lower frequency.
    Good idea, I'll see if I can borrow another camera.
    Don't really want to lose that recording unless I can confirm it's
    irretrievably corrupt, but I can see this is a sensible idea!
    Many many thanks for the input. I will report back here with my
    results (if any).
     
    H Bergeron, Aug 25, 2004
    #13
  14. H Bergeron

    Jukka Aho Guest

    You might also want to try playing back the offending tapes
    in your camera, but connected to some other computer (with a
    known-good Firewire setup.)
     
    Jukka Aho, Aug 26, 2004
    #14
  15. H Bergeron

    mrlipring Guest



    Have you tried recording in sp and lp to see if it makes any difference?
     
    mrlipring, Aug 26, 2004
    #15
  16. H Bergeron

    mrlipring Guest

    I think that the fact that it only happens with tapes, several tapes at
    that, and is reliably repeatable, rules out the pc. If we just record what
    the camera's currently seeing, everything works fine, and takes all pc
    issues (especially those of memory...) out of the equation.

    Actually though, what DV codecs does the op have installed?
     
    mrlipring, Aug 26, 2004
    #16
  17. H Bergeron

    mrlipring Guest

    He does this every time though. No matter whether he knows what he's talking
    about, no matter whether he's read the thread properly or not, he answers
    and offers "advice". It's not advice. Not good advice at least, he's almost
    always wrong from what i've seen. I don't doubt he knows "stuff", he just
    talks about stuff he knows nothing about far too much.

    Giving someone bad advice is worse than sitting back and letting the more
    knowledgeable step in.
     
    mrlipring, Aug 26, 2004
    #17
  18. H Bergeron

    John Russell Guest

    But wouldn't a camera equipped with good drop out correction use that to fix
    the DV out, not just the displayed LCD image?
     
    John Russell, Aug 26, 2004
    #18
  19. H Bergeron

    :::Jerry:::: Guest

    [ re Mr Morgan ]
    You're new around here, aren't you....
     
    :::Jerry::::, Aug 26, 2004
    #19
  20. H Bergeron

    SjT Guest

    There's nothing i like more than finding a love letter from H Bergeron
    What are you using to capture?

    And are you using the same capture utility to capture your live ccd
    footage as your recorded footage?

    Maybe you could try a standalone capure utility if you havent already?

    I cannot get my head around this at all, when you view the footage
    back is it definetly present in the footage and not being generated as
    you watch it? i.e. check the waveforms for these sound abnormalities
    to make sure they really are in the recording, and slow the footage
    down in your editing software to check whether the image problems
    appear in slow motion too.

    Also, if you have DV In on your camera maybe you could copy back to
    another tape and see how the video camera plays it back after its been
    in your computer, if it plays it back fine then obviously the stream
    that is captured is unprocessed by the camera, and maybe this could be
    the fault? -Confused- :(
     
    SjT, Aug 26, 2004
    #20
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