quality loss during capture on my iMac G4

Discussion in 'Professional Video Production' started by Dave Rice, Aug 18, 2003.

  1. Dave Rice

    Dave Rice Guest

    This is a new problem on my iMac and I haven't found a solution for
    it.
    I have an iMac G4 with iMovie and Final Cut Express 4. I am importing
    miniDV, NTSC, through Firewire.

    When previewing the clip in the "Log and Capture" window all looks
    fine, but once I hit Capture Now or Capture Clip, the capture window
    opens with significant quality loss (as if overcompressed). The
    capture clips retains this loss through editing, exporting, etc. The
    captured clip is still 720 x 480 pixels as it should be but compressed
    looking.

    I tried importing in iMovie and had the exact same problem. Previewing
    off the tape looks fine, but once capturing starts there's a heavily
    compressed look.

    Can anyone offer advise here?
    Dave
     
    Dave Rice, Aug 18, 2003
    #1
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  2. Dave Rice

    Ed Anson Guest

    Dave,

    Check your settings. What you describe is a selectable option. Make sure
    you have selected high quality video, and capture again.
     
    Ed Anson, Aug 18, 2003
    #2
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  3. Dave Rice

    Dave Rice Guest

    I've been over my settings in the "log and capture" window I selected
    "Firewire NTSC" for device control, "DV NTSC 48 kHZ" for
    Capture/Input. Under render control on user preferences I have 100%
    selected for frame rate and resolution.

    I just tried deleting my FCP preferences file and retrying but that
    didn't help.

    Because this problem of unwanted compression during capture happens in
    iMovie as well, I wonder if this is a hardware problem. Basically
    footage in the "log and capture" window looks much better than
    anything captured or exported, whereas on my last editing project on
    the same computer captured video was not noticeably different.

    Dave
     
    Dave Rice, Aug 18, 2003
    #3
  4. Dave Rice

    Ed Anson Guest

    It doesn't sound like a hardware problem to me. If you had a hardware
    problem, you wouldn't be getting good video in the "log and capture"
    window either. It really sounds like you have somehow gotten it into a
    mode of low resolution capture.

    One more thing to try, that I can think of. QuickTime is involved in the
    capture process. You might try checking (or deleting) its preferences as
    well. If that doesn't help, I'm out of ideas. Good luck.
     
    Ed Anson, Aug 18, 2003
    #4
  5. Dave Rice

    Ken Peterson Guest

    No, no! There's no problem here! What you see is merely a temporary
    decrease in *monitoring* resolution so more CPU time can be used doing
    the capture. What is recorded to HD is exactly what you are feeding in,
    at the resolution and framerate of the original. I think you will
    suffer dropped frames before there is a loss of quality, and that is
    what the software tries to avoid.

    Then ... how your captured video is displayed depends on the player,
    and some are fuzzy-looking (QuickTIme 6). The previewer in FCP
    Compressor is sharp, I seem to recall. The excellent but idiosyncratic
    VLC Player for OSX is somewhere in the middle. The slug viewer (left
    window) in FCP 4 is also perfectly sharp.

    Also, remember that you get a horizontally stretched picture is you
    show what the CPU has the easiest time doing: pixel-for-pixel display.
    If you force the correct aspect ratio (4:3), the computer now has to
    interpolate some pixels.
     
    Ken Peterson, Aug 19, 2003
    #5
  6. Dave Rice

    Dave Rice Guest

    Thanks Ken,

    Unfortunately the clips I'm capturing don't just look fuzzy, they Are
    fuzzy.

    This is an example of the quality I used to capture (I'm not sure what
    I did to cause a change).
    http://homepage.mac.com/daverice/iMovieTheater3.html

    This is what capture look like now.
    http://homepage.mac.com/daverice/iMovieTheater4.html

    I'm using the same firewire cable with a Canon ZR40, exact same tape.
    What I find interesting is that all captured footage looks fuzzy
    whether in iMovie, FCP, and I even downloaded HackTV and it happened
    there to. I've deleted my quicktime preferences, tried creating a new
    user to capture, verified and repaired permissions, etc.

    At this time my options seem to be, to backup everything and erase the
    hard drive and bring things back or to fork over the dough to extended
    Applecare so I can get some professional assistance. I'm hoping
    Applecare would help in this situation because the problem does not
    seem to be in any one piece of software. I doubt that firewire cable
    is damaged because in FCP I can preview the source tape at the
    original quality, but once I hit the capture button, quality drops and
    stays there.

    So the problem is that in any capturing program, what my hard drive
    receives is not of the quality of what is coming in. Is there
    something unwelcoming that is compressing the footage for some reason.
    Does this sound like a hardware problem?

    Dave
     
    Dave Rice, Aug 19, 2003
    #6
  7. Dave Rice

    Ken Peterson Guest

    I looked carefully at the frames in FCP4. You're right; the second
    example is (selectively) blurry.

    Given the trashing of pixels I see in some diagonal lines, it appears
    as though the picture has gone thru some sort of transcoding with loss
    of information. Normally, a capture from a camera's VTR is a literal
    one: You get the exact same digital information, without processing.
    Your second image looks *processed*! In fact, part of it looks like it
    was reduced in resolution, then upped again to 720 X 480.
    Paradoxically, it seems like only part of the image has deteriorated:
    the edges of the window and the guy's light shirt. The more subtle
    diagonal lines on the ceiling seem the same on both samples. Weird!

    Have you inadvertently changed a preference or setting somewhere? I'm
    not familiar with that camera, but you might go thru the menus to see
    if there is an option to export as lower-res QuickTime or something. Or
    might you have changed preferences on the capturing application to
    re-code it on input (Far-fetched, perhaps). You want the format for
    getting it out of the camera to be "DV-NTSC.

    But it has all the signs of an image that has been up-sampled from a
    lower resolution. Thing is, where was that lower resolution set?

    "Capture then" has a data rate of 7.4 MB/sec, and the compressor is
    identified only as "Video."

    "Capture now" (the problematic one) has a listed data rate of only 5.4
    MB/sec and a compressor of "DV/DVDCPRO-NTSC." A lower data rate??

    Obviously I'm doing a lot of thinking out loud, here. Some detective
    work is in order! But I meant what I said originally: The monitor
    window has sucky quality and framerate during capture with most
    capturing applications. You have to look at the captured video later to
    see what you've got. (It worried me, too.) I use FCP4, iMovie, and BTV
    Pro Carbon under OSX 10.2.6 on a G4/933/1.5GB RAM to capture. Haven't
    had any grief yet.

    Ah! One more comment: What *doesn't* seem to work is capturing from a
    DV deck via FireWire to a hard drive *on the same FireWire bus.* On my
    17" iMac, the whole thing simply chokes immediately unless I capture to
    the *internal* hard drive. On my G4/933, it almost works: after a few
    minutes, it chokes, too. I put in a separate PCI FireWire card, and now
    captures to an external 200GB FireWire drive via the PCI card are
    flawless. Go figure! Wonder if your software/hardware combo is topping
    out its bandwidth just on the edge of failure. I dunno . . . It would
    piss me off, too!
     
    Ken Peterson, Aug 19, 2003
    #7
  8. Dave Rice

    Ed Anson Guest

    DV/DVDCPRO-NTSC is what I use, and without any resolution problems. But
    my data rate is 3.6 MB/sec. I wonder what accounts for the difference here.
    Yes, there can sometimes be a bandwidth issue with FireWire, but I don't
    think that's the OP's problem. If it were, he would be dropping frames
    or just aborting the capture. There is no provision for reducing
    resolution in this case.

    I agree that this sounds like a case of reprocessing the video to reduce
    its resolution. But the fact that he has trashed the preferences would
    _seem_ to rule that out. Perhaps there's a loophold somewhere.
     
    Ed Anson, Aug 19, 2003
    #8
  9. Dave Rice

    Dave Rice Guest

    Dear Ken and Ed,

    To answers your ideas: I am not getting any dropped frames or aborted
    captures. All captures have been done directly to my hard drive,
    nothing to an external drive. As I should, I have "DV-NTSC" selected.
    I am obsessing a bit about this too and this is one of the reasons I
    love FCP's recapturing options so that this does not prevent me from
    editing.
    I do not have any other Firewire component to capture from, but this
    weekend I'm going to friend's house. He has a iMac G3 running iMovie
    and I think he has Final Cut Express. I'll try my camera and firewire
    cord there.

    Here's a little more detail about what happens in my log and capture
    window (not the window that pops up while capturing):
    When the tape is playing or pausing I get a great image, no problems.
    When it's playing and I hit pause and vice versa, I get one frame that
    looks like crap, just like what I've been capturing. Rewinding or fast
    forwarding also produce this quality. If I remember right rewinding
    and fast forwarding did not affect the quality of the log and capture
    window, but only strobed the frame. Also exactly when I hit the
    capture button quality drops only a little in the log and capture
    window (diagonals become pixelated), but this is understanding as more
    CPU is opening and preparing the capture. But then in the capture
    window it's crappy again.

    Thanks,
    Dave
     
    Dave Rice, Aug 20, 2003
    #9
  10. Dave Rice

    Ken Peterson Guest

    Yup. Detective work required. Try your camera with friend's computer.
    (His iMac is way underpowered, but hey . . .) I would really try to
    find a way to use a different video source with *your* computer to
    complete the logic of the tests.

    With truly sympathetic wishes for good luck in getting to the bottom of
    this,
     
    Ken Peterson, Aug 20, 2003
    #10
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