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Re: SDI PAL progressive output looks bad

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Mark Spano
Re: SDI PAL progressive output looks bad
on Nov 1, 2011 at 3:31:15 pm

This doesn't surprise me, since I believe 25p PAL is not in the standard definition spec for SDI. 25p PAL exists only inside your computer. As soon as it goes out over SDI, it has to be interlaced. This is usually not a problem, as I said before:

DigiBeta is always interlaced. To get video onto DigiBeta tape, it has to go down as 720x576 / 25i. So the Decklink is doing you a favor by taking your progressive signal and splitting the frames into fields.

So your 25p PAL signal is 25 frames per second, progressive. This gets translated by the Decklink into 50 fields per second, interlaced. There is no degradation or signal loss. The 50i signal goes to tape and is 50i on DigiBeta, since DigiBeta is interlaced. I'll say it again: DigiBeta is interlaced. You can't change that. So the card is doing it correctly. This 50i interpolation is the best (and only) possible way for your 25p PAL stuff to get to tape.

If you want true progressive, you need to go HD, at 1280x720 50p.

If you're concerned about quality, look at your signal and monitoring path. This is the only advice I can give based on what you have provided.

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