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Old July 5th, 2005, 08:28 PM   #1
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problems with capturing interlaced DV over firewire.


Sorry if this is in the wrong area, I did look but couldn't find anything that addressed the issues I'm having. I want to start editing DV on my mac (dual 2.7 Ghz G5, 2Gb RAM, geforce 6800 ultra, 400Gb HD) using Final Cut Express HD but having serious problems with the quality of captured DV footage from a PAL Canon MXV250i. (I want to learn the ropes on this camera before investing in a JVC HD101E)

I've read here that interlaced video always looks bad on progressive displayed because both fields are displayed simultaneously, however what I'm seeing seems to be really bad. I connect the camera DV out into my mac, load up FC, start a new project, select the apple PAL codec, press play on the transport and then 'capture now'. It all seems to work fine, I get footage, only the detail seems about half what it should be. At 100% scale, besides the interlacing effects the picture seems slightly pixelated. When I pause on the camera and zoom into a frame displayed on the flip out screen there definitely seems to be more information there (I know it smoothes the picture, still there does seem to be more detail). I've taken a in-camera VGA frame grab, significantly jpg compressed and displaying it on my computer again shows a better picture, by which I mean more detail and less interlacing artefacts. What's going on here?

Thinking that it might be some playback issue I encoded some footage using the H264 codec on the 'high' quality, multipass setting at original source resolution, PAL (btw it took my dual 2.7Ghz G5 over 24 hrs to encode 90 minutes of DV on this setting, not sure if that's normal...). The result was fantastic, in terms of being indistinguishable from the the captured DV, when there was no motion but there were terrible artefacts that look like interlacing with a half second offset between fields for any movement. What's going on there?

I tried capturing (at device native resolution) using quicktime 7 pro and I get the same results as for FC, only now when playing back at 'full resolution the picture is half PAL size. Double size play back looks exactly the same as the capture from FC. Anyway I tried doing the same from my powerbook and got exactly the same results, so it's not not my computer.

Anyone else had similar problems? Any suggested fixes? All help much appreciated!

I've put together a webpage with some screen shots of my footage that show what I mean here:

many thanks!
Joe Hudson is offline   Reply With Quote
Old July 6th, 2005, 01:10 PM   #2
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Couple of things:

The only way to truely preview your DV is to have a TV hooked up to your camera. Final Cut will output to your TV & you can get a much beter idea of what the final product will look like. Here's my setup: Firewire from camerma to Mac. S video from camera to TV. Camera in VCR mode. I edit watching my computer screen & then run a preview from the timeline watching the TV. It's a bit of a pain, but from what I've seen first hand & read on line, it's the only way to go.

Still captures from video: Only way I've been able to get decent freeze frames or exported stills, is to use the deinterlace filter in Final Cut. I added a few freeze frames to some kayaking footage & they looked great on my Mac, but looked awful on TV. Applied the deinterlace filter to just the freeze frame clips, rendered & all was well.
John Snoddy is offline   Reply With Quote
Old July 12th, 2005, 05:37 PM   #3
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thanks John,

I noticed by chance that iMovie automatically deinterlaces interlaced DV. The result actually looked quite good, pretty much what I was seeing plugging the camera into the TV in terms of detail and sharpness. (although strangely when iMovie scales to 'full DV' size I get a 640x480 pixel size video window, not PAL 720x576...) So I guess it was a question of deinterlacing afterall. Odd that quicktime Pro doesn't do this, or at least have the option.

So I went back to Final Cut HD Express 3 and tried the deinterlace there. It was certainly an improvement but actually didn't look as good as the job iMovie did, being more pixelated (I guess because the standard algorithm is throwing away half the lines). Then I switched to 'Flicker Filter (max)' and the picture looked every bit as sharp as what I was seeing from iMovie, only full PAL size. great!
Joe Hudson is offline   Reply With Quote
Old July 13th, 2005, 06:57 AM   #4
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Joe: That frame grab looks typical to me of interlaced DV with motion. You shouldn't have any issues capturing PAL in FCP, I just finished a big project using PAL (shooting with Sony Z1, plus a lot of computer animation).

I agree that you shouldn't base your judgement on what you see on the computer screen in FCE or FCP. It's a less than full quality image. Also, if viewing the file directly in Quicktime, use Get Movie Properties > Video Track > Quality and enable high quality by the checkbox (this probably is only available in Quictime Pro). That will make a big difference in what you see on the computer screen.

Deinterlacing can mean different things. The most basic form just involves discarding either the odd or even field and results in a 50% resolution loss. This might appear sharper but you're throwing away half your data. Better software does "adaptive deinterlacing" and treats the static and moving areas of the image differently to get the best results. See the software I suggested in your other thread for more on this.
Boyd Ostroff is offline   Reply

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