FORUMS: list search recent posts

More serrated SD downconvert

COW Forums : AJA Video Systems

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
George
More serrated SD downconvert
on May 25, 2007 at 9:35:52 pm

Has anyone had success with the realtime downconvert to uncompressed 8 or 10 bit BetaCam component feature of the Kona LH from an HDV 720p30 timeline?

Link to a frame showing the effect I am getting -

http://briefcase.yahoo.com/bc/twosundogs/lst?.dir=/Serrat...

This b&w image shows the coarse serations on the vertical edges of the animated block. It just moves left and right. 720p30 footage from JVC cameras have the same "fringe", but it's not as clear on the scenes I'm testing.

Anyone know how to make this work?

George
Light Images


Return to posts index

JeremyG
Re: More serrated SD downconvert
on May 25, 2007 at 10:30:03 pm

That looks like regular ole interlace to me.


Return to posts index

George
Re: More serrated SD downconvert
on May 25, 2007 at 11:38:39 pm

Except this one looks this way in motion then gets smooth when the video pauses. Regular interlace is less coarse and works the other way, smooth in motion, serrated when paused.

The serration artifacts are seen on an NTSC monitor and on BetaCamSP tape when doing downconversion.

George
Light Images


Return to posts index


JeremyG
Re: More serrated SD downconvert
on May 25, 2007 at 11:45:51 pm

Mmm, I wouldn't call regular interlace less coarse, your picture looks like interlace...interleaved lines.

Is your HDV sequence setup to render progressive?


Jeremy


Return to posts index

George
Re: More serrated SD downconvert
on May 26, 2007 at 3:35:43 pm

Jeremy

All of this is visible on an interlace CRT broadcast SD monitor. Much of it doesn't show on a progressive computer diplay.

It's definately more coarse than regular interlace, by about twice. Though it is the same sort of pattern, the interlace is fatter and seems to be phase reversed from normal interlace. It isn't a field dominance issue.

The HDV (or every other) sequence tested is progressive. The error seems to be in the HDV codec conversion to SD component BetaCamSP, even if the HDV codec has been transcoded to another codec.

For animation I can eliminate this artifact by creating a fresh animation on an uncompressed Kona 720p59.94, DVCPro HD 720p60 or DVCPro HD 720p30 sequence.

A reference movie from an HDV 720p30 or AIC HDV 720p30 sequence with the test animation will carry the error forward to any of the "better" codecs.

720p30 or 720p24 clips from a JVC HD100 or HD250 always have this wierd interlace bug on transcode to SD BetaCamSP no mater how they are captured.

So it is following the HDV compression.

AJA support hasn't been able to figure it out yet. I am hoping someone on this board has seen this and knows what is wrong.


This is from my original post that didn't get any response -

I am having trouble down converting HD to SD Component (Beta) through a Kona LH.

Down conversion looks coarsely serrated on objects moving cross screen and diagonals are jaggy when playing but smooth out when paused.

It's just the opposite of watching normal interlaced SD that shows the interlaced fields when paused, smooth when playing.

Sources have been HDV 720p30 captured from firewire as HDV and AIC, captured from component as uncompressed Kona 720p59.94, DVCPro HD 720p60 and DVCPro HD 720p30.

SDI Out 1 set to whichever format the test clip was captured.

SDI Out 2 set to 525i29.97/crop to Ensemble Serial Box 1 to Sony PVM1344Q component monitor.

Analog Out set to Secondary 525i29.97/Component (Beta) to PVM1344Q.

All results are identical.

George
Light Images


Return to posts index

JeremyG
Re: More serrated SD downconvert
on May 27, 2007 at 12:36:27 am

If AJA doesn't know, I certainly can't help you except to say you might want to move that project out of HDV.

Jeremy


Return to posts index


Tom Brooks
Re: More serrated SD downconvert
on May 27, 2007 at 11:39:20 am

Is it possible that what you are seeing is the inter-frame motion of the 59.94p frames? In other words, let's say your camera actually records 59.94p and FCP has to remove duplicate frames during capture. But duplicate frames are not removed for some reason--option not checked for instance. In the downconvert, both of the 59.94p frames are displayed within the 29.97p frame. So, whenever there is motion, there is a stair-step caused by the display of both 59.94p frames as one 29.97p frame. I don't know if this happens or is possible, but it's a theory. On still subjects you wont see it because both 59.94p frames will look essentially the same--no inter-frame motion.

I do wish someone could explain this. I've had a similar issue with 59.94p shot with a Panasonic HVX-200 and encoded to MPEG-2 for SD DVD. On moving subjects, there is an ugly, big stair-step or jaggie. I haven't found the way to get rid of it completely. Using the Panasonic frame rate converter doesn't work because the speed gets cut in half--unless I'm missing a setting in the FRC.

Anyhow, I don't want to hijack this post to another subject, but to propose the above theory.


Return to posts index

George
Re: More serrated SD downconvert
on May 27, 2007 at 11:56:10 pm

This was shot on a JVC HD100U in true progressive. The camera has progressive chips and records in real progressive frames, though 720p30 is nominal. The correct frame rate is actually 720p29.97. No pull down involved on this according to JVC.

Were you seeing these artifacts on an interlaced CRT monitor? Did you find the stair step/jaggie went away on pause and came back on play?

George
Light Images


Return to posts index

Tom Brooks
Re: More serrated SD downconvert
on Jun 5, 2007 at 1:56:41 pm

George,
My experience with HD has been 720 60p (59.94 that is) thus far. It was shot with a Panasonic HVX-200 on P2 media, so it's true progressive at 59.94fps. The downconvert to SD 29.97 does show the jaggies only when the subject or camera is in motion and only certain types of subject matter. It only shows up on hard-edged diagonal lines. The jaggies go away when the timeline is paused. The jaggies only show up on an interlaced display, not on thePanasonic TH-37PH9UK. I call these jaggies because it's a sort of blocky jaggedness, rather than a comb-like look as is usual from interlacing. I get the same jaggies from a real-time down-convert on the Kona LHe and from a down-convert to MPEG-2 through Compressor. My SD monitor is a Sony PVM 1220. It's ancient, but in good shape and properly calibrated. I suspect it's just the nature of 59.94p. What I'd like to try is to convert it to 29.97p, but I have not found a way to do that by dropping frames from the original 59.94p source. Not sure how or if this relates to your situation, but here it is FWIW!
-Tom


Return to posts index


George
Re: More serrated SD downconvert
on May 28, 2007 at 12:05:06 am

Jeremy

Unfortunately it won't come out of HDV without carrying this problem with it.

Btw, I wasn't saying AJA can't solve the problem. They just don't have an answer yet.

George
Light Images


Return to posts index

JeremyG
Re: More serrated SD downconvert
on May 28, 2007 at 12:29:28 am

So even if you capture to DVCPro HD, it does this? I thought you said it didn't?

Jeremy


Return to posts index

George
Re: More serrated SD downconvert
on May 28, 2007 at 11:05:27 am

If I create an animation in DVCPro HD, the downconvert is fine.

If I capture JVC HD100U 720p30 footage as DVCPro HD the problem stays with the footage.

If I make a simple animation in an HDV 720p30 sequence, save as a reference movie and bring that into a DVCPro HD timeline, the problem stays.

It's the same for Kona 720p59.94 sequences.

It seems to be an HDV issue, not just a JVC issue, since animations created in the HDV 720p30 codec inherit the disease.

George
Light Images


Return to posts index

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