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SDI PAL progressive output looks bad

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slobodan milivojevic
SDI PAL progressive output looks bad
on Oct 28, 2011 at 4:56:02 pm

I spotted a big problem today when exporting PAL progressive animation videos to SDI/DIGIBETA on DECLINK EXTREME HD. I noticed judged edges on graphics, like the video is being deinterlaced.

I have tried on both default sequence setting (with upper field) and no fileds setting and I have the same output.

Is it possible that card is by default reading video as interlaced? Source video is rendered in After effects, progressive PAL WIDESCREEN uncompressed Microsoft AVI. Video looks good when I watch it in Media Player.

I have the latest drivers installed, Windows 7 x64....

Director/Editor/Postproduction manager
@ Talking Pictures productions Bahrain
http://www.youtube.com/bobansky


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Mark Spano
Re: SDI PAL progressive output looks bad
on Oct 28, 2011 at 8:35:49 pm

What is your signal path to monitoring? Assuming that it goes Decklink SDI to DigiBeta, DigiBeta SDI to LCD monitor, then you may be seeing the result of your signal being interlaced on the way to tape, then deinterlaced by the LCD monitor. 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. That gets recorded to tape - on playback, the only true way to see the exact quality of this is to view on a CRT, as all LCD and plasma screens are progressive displays and automatically do a deinterlace process before displaying.



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slobodan milivojevic
Re: SDI PAL progressive output looks bad
on Oct 28, 2011 at 8:49:34 pm

Hi,

I am monitoring it on CRT monitor. I have the same output on preview from Blackmagic, and also on Throughput from Digibeta....

Something is definitely wrong....I made few tests today, and YES, Blackmagic is deinterlacing Progressive video when playing out from timeline!

Director/Editor/Postproduction manager
@ Talking Pictures productions Bahrain
http://www.youtube.com/bobansky


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slobodan milivojevic
Re: SDI PAL progressive output looks bad
on Nov 1, 2011 at 2:18:07 pm

Hi guys, I just have received the most ridiculous answer from Blackmagic.
According to them BLACKMAGIC HD EXTREME does not support PAL PROGRESSIVE sygnal, and that's why I get deinterlaced output on monitor and DIGIBETA......Strange, but true..... :)

See below:
***********************
Hi Slobadan,

Thank you for your email.

The Decklink HD Extreme cards do not support progressive PAL signals. The outputs will always show an interlaced output if you are feeding it with PAL. I’m afraid that there is no way I can think of to get around this as it’s simply not something the card supports.

If I can help further however, please do get back to me.

Regards

xxxxx xxxxxxx
Technical Support Consultant
Blackmagic Design EMEA
**************


Director/Editor/Postproduction manager
@ Talking Pictures productions Bahrain
http://www.youtube.com/bobansky


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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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slobodan milivojevic
Re: SDI PAL progressive output looks bad
on Nov 1, 2011 at 8:38:07 pm

Hi, thanks for your detailed and kind answer...

I did few tests:
I upscaled my video to 720p, and then played it from BMD 720 p sequence, and it looks nice on my PAL CRT, just slightly blured (I guess it is from hardware down conversion to PAL.) Same video from PAL sequence, looks very bad, with jagged edges...
I am at home now, but will post how it looks in Premiere tomorrow...

Also, can you explain - what is the best way to interpolate my 25p animation to 50i?

Director/Editor/Postproduction manager
@ Talking Pictures productions Bahrain
http://www.youtube.com/bobansky


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slobodan milivojevic
Re: SDI PAL progressive output looks bad
on Nov 3, 2011 at 9:26:59 am

Hi Mark,

please see attached 2 images, and You will see what is my problem.
Source file is uncompressed Microsoft Avi, 25p, exported from After Effects.

1. BMD sequence is: PAL, widescreen (I got the same look in upper field sequnce or progressive sequence settings). File is interpreted as progressive in project window.



2. Other sequence is NON BLACK MAGIC, DV PAL WIDESCREEN,(its is NO FIELDS, but it looks the same if sequence setting is upper field).File is interpreted as progressive in project window.



Spot the difference on golden bar edges - this is what I am crying for!

Director/Editor/Postproduction manager
@ Talking Pictures productions Bahrain
http://www.youtube.com/bobansky


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Mark Spano
Re: SDI PAL progressive output looks bad
on Nov 3, 2011 at 1:50:33 pm

Well it's clear that the second one looks better than the first in these images. But what are we looking at? I mean, I always need to view output material on a broadcast monitor to judge true quality. You say these are widescreen, so clearly now in these images there's been a conversion to full height anamorphic, presumably for your tape output. There's another avenue where distortion could take place that you wouldn't necessarily be able to judge unless you're looking at the tape output. The screenshots - are they of a 100% raster viewer window? I know that I can't judge anything accurately on my computer screen unless I'm looking at a 100% size viewer. And even then, the viewer is showing either a single field, or two fields blended, so that's no way to judge for interlacing effects. Both of these could look identical when played out to a CRT. So we're back to the question of proper workflow. You are rendering out of AE as what codec? AVI is a container, so what's inside? I would use either Animation codec (this is called Lossless) or straight to Apple ProRes. Thinking that it's a progressive animation, I'd render without fields, scaled to the output resolution (720x576, 25fps). Then you're making sure AE is handling any scaling involved, which is probably better than Premiere/FCP/MC. I'd import the video straight to a sequence that matches the codec/fps/field order of the source. That's really it. I don't see how it can get messed up in that workflow. The card will handle the interlacing to get it out to display/tape. But this will look identical to your progressive animation, so it won't matter that the output is interlaced as you won't see any interlacing lines. Note that I am not talking about the computer screen viewer, as I mentioned before, that is not reliable to judge for quality. Only the actual video output from the card is important. If it is still not to your satisfaction, then there may actually be something wrong with the hardware, and you may need to contact the manufacturer.



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