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Random flashing pixels in DV setting vs. Uncompressed
Alright, here’s the whole, frustrating deal. I’m using FCP 5 on a Mac G5 with a 1.5 TB Medea array and the ever-versatile AJA IO for output. (All of my INPUT is currently limited to DV firewire – don’t ask.) I’ve been having problems with random square pixels popping up in my video when I play back off of the timeline. Unfortunately, these little scoundrels are NOT on the original source footage – NEITHER are they permanently on the timeline – if I back the playhead up and start again often the video is clean until they pop up somewhere else. Yes, they do print to tape, and yes, they even manage to squeeze into exported quicktime movies.
However, I think I may have discovered part of the problem. I exported two differernt quicktime movies of the same project – one at DV quality and the other at Uncompressed 8-bit. The DV version had flashing pixel problems – the Uncompressed did not!! So I’m wondering if I export everything as uncompressed quicktime and then re-import it and print to tape that way… maybe it would work. This, however, is a huge pain because while some of my projects are 30 seconds long, others are over an hour which tends to eat up much of my available space – to say nothing of the time I consume rendering these things. (AND the time spent eyeballing the final print to make sure the flashes don’t pop.) Does anyone have any earthly idea what could be going on? ALL input is greatly appreciated. -
2 Replies
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In short, you’ve basically said that your system dislplays random flashing pixel boxes on all DV playback, but never on uncompressed playback.
You mention that it occurs even in exported DV clips. My theory is that it does not get squeezed into exported DV clips as you say, but instead those clips simply suffer from the same DV playback problems. Random playback problems simply do not randomly find their way into exported clips. It just doesn’t work that way. The fact that your uncompressed clips are fine are evidence of this.
My guess is the odd combination of catpuring DV over firewire and playing it back over AJA IO is the source of your problem. I’m not sure exactly why there should be something there. AJA natively plays back and captures uncompressed clips. Using DV material with AJA requires rendering or on the fly processing.
So for output, I’d suggest you create a standard IO sequence that is for uncompressed material, and place your DV footage into the sequence and render. It may say it can play it back in real time, but you’re obviously getting some sort of data bottleneck issue. Sounds like the system isn’t dropping frames, but is having some sort of problem processing the DV into uncompressed material on the fly.
If all your material is DV, try using just a DV sequence and outputting via a DV device like a DV deck or camera hooked up to a ntsc monitor and see if you get the same problem.
The whole thing could be as simple as updating AJA drivers or QT, or reinstalling or updating both. Sometimes rebooting the AJA IO solves lots of issues.
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Thanks for the input!! I’ve been stumped and it’s good to catch some intelligent vibes. Unfortunately, the flashing pixels problem is not limited to AJA IO interaction. Even if I capture via firewire, edit in a DV NTSC sequence, and output via firewire, I get these little flashes. The flashes always occur both on my external monitor (getting it’s feed from AJA) and simultaneously on the computer monitor. The whole Uncompressed vs. DV revelation was a recently-found hopeful solution – however I tried exporting to an uncompressed quicktime, re-importing into an uncompressed sequence, and outputting via AJA -> s-video -> DV deck. (I realize the tremendous drop in quality, but at this point I’m merely trying to get a preview tape.) I don’t think I got any flashes, but I think the uncompressed feed was too much for this trashy little DV deck to handle – the video was swimmy and bad. Sigh. I’ve obviously got issues here. Any more thoughts? At this point (until I get a better deck in – which I’m told will happen soon), I would be content going firewire in and firewire out. As far as I’m concerned AJA doesn’t even need to play in the game right now (I know, it seems like a waste, but once I get the new deck in then AJA can function as it was meant to). I welcome any more musings…
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