FORUMS: list search recent posts

"Ghosting" on downconverted text

COW Forums : AJA Video Systems

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Tim McLaughlin
"Ghosting" on downconverted text
on Mar 17, 2008 at 10:45:58 pm

Okay, now I have a new term for what I'm seeing.

From August last year:

Re: Downconvert/Field Issues-Upper vs Lower?---ANYONE??
by Kevin Wild on Aug 15, 2007 at 12:32:54 pm

Just to be clear, the ghosting images we are seeing have nothing to do with HDV. It does it on the downconvert period, regardless of codec. I even tested uncompressed HD. Also to be clear, this is using the KonaLH. It's possible it's not an issue on the Kona 3. We have 3 LHe's and they all do it...as does the one at AJA tech support.

And also:

by John Pale on Aug 16, 2007 at 9:51:49 pm

I see it on my Kona 2, for what its worth. have not found a workaround.

--

Okay - this is EXACTLY the problem I'm seeing. I can't imagine that Walter or Gary would put up with this kind of image degredation on their masters going to air.

I doubt Bob Z. would install so many AJA cards if they had this problem.

I'm in contact with AJA tech support, but so far they seem to think that this problem occurs because my source footage is DVCProHD.

I have a VERY hard time believing that.

I cut some sample footage into an uncompressed 720p HD sequence (with animation codec titles), rendered it, and it still looked like crap on titles.

The footage was gorgeous, the titles were ghosted.

Someone please shed some light on this. I'm losing my mind.

Tim McLaughlin
Avid and Final Cut Pro Editor


Return to posts index

Tim McLaughlin
Re: "Ghosting" on downconverted text
on Mar 17, 2008 at 11:58:01 pm

Forgot the details:

FCP 5.1.4
OS 10.4.10
Quad Core G5 2.5 GHz
Kona 3 with K-box

Downconverting DVCProHD 720p via HDSDI to DVW-500.

All standard def stuff looks GREAT. 10 bit Uncompressed SD does NOT have this problem.

This seems to be a down conversion problem only.

Tim McLaughlin
Avid and Final Cut Pro Editor



Return to posts index

Paul Provost
Re: "Ghosting" on downconverted text
on Mar 18, 2008 at 3:12:42 pm

are you downconverting by just rendering out in an fcp timeline, or are you downconverting an hd timeline using the Kona card output to a deck?

Paul Provost
http://www.postandbeam.tv


Return to posts index


Tim McLaughlin
Re: "Ghosting" on downconverted text
on Mar 18, 2008 at 3:47:10 pm

Downconversion is happening entirely through the Kona 3 card.

I'm performing "edit to tape" from my HD timeline and having the Kona card downconvert via SDI as either letterbox or anamorphic and add the pulldown.




Return to posts index

Arnie Schlissel
Re: "Ghosting" on downconverted text
on Mar 18, 2008 at 4:04:40 pm

I have not seen that going from a 720P timeline to beta via the component out on a Kona 3.

What kind of monitor are you using for the downconvert? I try to monitor downconverts on a CRT, the LCD that we use doesn't show the whole story with SD interlaced footage.

Arnie

Now in post: Peristroika, a film by Slava Tsukerman

http://www.arniepix.com/blog


Return to posts index

Aaron Neitz
Re: "Ghosting" on downconverted text
on Mar 19, 2008 at 4:43:10 pm

Now I'm confused... you said you were using Kona LHe or Kona 3?

Can you digitize a digibeta that you made with these ghosted text and post a still image for us? I think that'll help tremendously.



Return to posts index


Aaron Neitz
Re: "Ghosting" on downconverted text
on Mar 19, 2008 at 4:46:32 pm

Also like I asked earlier, are you certain you have broadcast safe titles?

The only reason I ask is on an old project for HDCAM-SR which we were peaking at 110 (this was for filmout, no broadcast safe needed to be adheared to) any downconvert to SD showed a weird ghosty/ringy quality in solid graphics and gradients. Disclaimer: this was using a Blackmagic card



Return to posts index

gary adcock
Re: "Ghosting" on downconverted text
on Mar 19, 2008 at 5:12:31 pm

[Aaron Neitz] "Also like I asked earlier, are you certain you have broadcast safe titles? "

Aaron

Good question, I would Like to also ask about the fonts being used. Thin or fine fonts
do not look good in SD, while the fine detail holds up in HD the inter-field blurring brought on by not having enough data when doing a conversion can bring this on.

My test - Use a standard title in SD and the same in HD downcoverted should look the same, and in all of my tests they do. Only on very fine text detail when doing an HD downconversion does it break apart or ghost. - it means that your font is NOT suitable for SD viewing.




gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD




Return to posts index

Tim McLaughlin
Re: "Ghosting" on downconverted text
on Mar 19, 2008 at 6:19:06 pm

Thanks for the feedback and questions guys.

Here is a link to hi-rez JPEG files as well as a zipped archive of TIF files that I've compiled.

One file is the original HD, one is a 10 bit capture from the SD downconvert, and one is a totally unfair comparison by taking the HD frame and resizing it in PhotoShop.

As a test, I readjusted the levels of the name keys in AE (to a range of 16 to 235), and I was still seeing the same issue.

I just need an answer on how to fix this - or if it's even fixable. Am I doing something wrong? Does DVCProHD always look like crap on downconversions? Is there something wrong with my card?

Tim McLaughlin
Avid and Final Cut Pro Editor



Return to posts index


Aaron Neitz
Re: "Ghosting" on downconverted text
on Mar 19, 2008 at 9:44:39 pm

Ah, I see

I see this on downconversions too. It's a function of that strong primary color, white type, and hard edges. There's probably some YUV maths involved in going from a 4:2:2 HD space into a 4:2:2 SD space... That's why Photoshop does such a good job - it's pre-sampling your HD as 4:4:4 RGB.

Did you try letting Compressor do a downconvert? Or dropping the HD timeline into an SD with Best rendering?





Return to posts index

Tim McLaughlin
Re: "Ghosting" on downconverted text
on Mar 19, 2008 at 9:49:12 pm

Letting Compressor or FCP handle this makes it look even worse. The interlacing artifacts are terrible.

I'd take ghosted titles over those 2 options.

Tim McLaughlin
Avid and Final Cut Pro Editor



Return to posts index

Kevin Wild
Re: "Ghosting" on downconverted text
on Mar 22, 2008 at 6:38:47 am

Tim, I'm sorry to see you are having problems, but I sure am glad I wasn't the only one experiencing these issues! I know AJA's support is usually very good, but after I spent an hour on the phone with them, sent them pictures of what I was seeing...they had agreed there was a problem. Then, zero followup with me and it was not corrected. I don't get why more people are not seeing this. We have 3 different configs (intel, 2 G5's) going to 3 different monitors and all 3 show this problem. It is obviously a downconvert bug.

The good news, is there is a work around. (At least it works for us.) The secret is to export your HD sequence first and then bring it back into FCP and drop it in the SD timeline. This should fix it. Then, you just play out SD 8 bit and it looks fine. This works for us also, because we usually save an HD version for archive anyways. Basically, this is bypassing the downconvert, but it doesn't take long to export and re-import.

Hope that helps. Let me know.

Kevin



Return to posts index


Francois Stark
So then: choose n Kona LHe...
on Mar 24, 2008 at 4:25:57 pm

So why not just use the LHe... It seems kona 3's hardware downconvert (The one feature I would use) is inferior to the export-HD-import-into-FCP-SD timeline method.

It will take a bit longer: Export ref HD movie, import, throw on SD timeline, render in SD... play out.

$1 000 cheaper, and better visual quality... No contest.


Regards
Francois


Return to posts index

Tim McLaughlin
Re: So then: choose n Kona LHe...
on Mar 25, 2008 at 11:11:15 pm

Evidently you've never seen what that looks like. FCP does not do a wonderful job scaling HD to SD and then adding pulldown.

Interlacing artifacts all over. Looks worse than the ghosting.

Tim McLaughlin
Avid and Final Cut Editor



Return to posts index

Paul Provost
Re: So then: choose n Kona LHe...
on Mar 25, 2008 at 11:13:13 pm

way worse. expect major aliasing...

Paul Provost
http://www.postandbeam.tv


Return to posts index


Ramona Howard
Re: So then: choose n Kona LHe...
on Mar 26, 2008 at 12:02:40 am

Francois,

"It seems kona 3's hardware downconvert (The one feature I would use) is inferior to the export-HD-import-into-FCP-SD timeline method."

What tests are you doing to show this and what is the source content because the K3 is used daily in a high-end environment with excellent results. There are many things that could be contributing to the poor look of the downconvert your doing. Remember HD and SD are very different and even the codec may be the contributing factor in your poor results.

Cheers,
Ramona



Return to posts index

Jason Lyons
Re: "Ghosting" on downconverted text
on Oct 25, 2008 at 10:22:58 pm

Just chiming in here.. I recently ran across this issue. HDV 1080i using AJA Kona 2 to downconvert. So I selected selected the correct setting in FCP Video Playback settings (AJA Kona 1080i 29.97 8bit(1920x1080). Whammmo when monitoring the down-convert titles were all ghosting. Even detail in my program was ghosting. Called AJA, they as always were extremely helpful, we replaced the Kona2 card. Same thing.

I tried, FCP Video Playback settings (AJA Kona 1080p 29.97 8bit(1920x1080). And the ghosting went away. What is up with that! ? So my options are reduced to laying out a 1080p program (which is actually interlaced) or one that has ghosted images. I chose to lay out 1080p as it was the lesser of two evils.... hmmm this reminds me of another lesser of two evils dilemma to be hashed out on Nov. 4th.






Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]