HDV downconvert to DV - issues

DJPadre wrote on 11/28/2007, 10:44 PM
OK,, well im working on some in cam downconverted HDV from an A1.
Now in Vegas th footage shows up as 4:3 so i have to go into the clip properties and change this to 16:9

From there, it shows me that the downconverted DV is in upper field first. Now usually I woudnt have a problem with this, becuae im converting to progressive scan anyway.

Now i add several filters in a chain, mainly levels, curves, colour balance, BW and MB2

Using a variety of compbos of filters to teh point of even turning them all off, my prerender tests show a real strange problem
Now as they plaback in normal speed, it looks fine, BUT as son as i throw on some slowmotion, its looks like tehyre taking 1 step forward and 1 step back.. stuttering and looking like absolute shite..

Now with standard DV, source footage at lower field first, i never had this issue.

It looks as though there is a field swap issue happening here before the frames are interpolated into progressive.
The deinterlace method im using is interpolate, but ive jsut tried blend and its jsut as bad..

removing some of the filters, and the issue cleans itself up.
The slowmo is a clean 50% so each field should in turn become its own repective frame. I speed it up from 50 to 60, and ths issue clears up a bit but its still very staggering.
As it stands its unusable, so i need to rn this through Dynapel Slowmotion which is good, but very slow...

Any ideas?? This is really starting to piss me off and i have a delivery tonight with this and i cant deliver it if it looks like this...

thoughts??? ideas?? Now as this is DV, im assuming tha teh IBP profiling (Long gop sequence) of the MPG source shouldnt play a part in this as the proceeding frames are drawn and captured as Intra DV. So this slowmotion issue shouldnt have anything to do with long gop.

Anyone?

Comments

farss wrote on 11/28/2007, 11:14 PM
The motion afflication you're describing sure sounds like a field order reversal however once it's progressive it cannot have any effect, right.

However someone here did say that Vegas doesn't do slomo well at all with progressive, maybe that's the limitation you've struck. Perhaps slomo it before de-interlacing?

Bob.
DJPadre wrote on 11/28/2007, 11:49 PM
Yup, tried that too..

In fact, analysing the footage, it seems that the field order is indeed being reversed as im getting some horendous flicker in the upper 5 or 10 rows of resolution, in addition to the stuttery motion of the footage itself.

Now with the method i was using, i was rendering from interlacded DV source (form downconverted HDV) so even if it was upper or lower, it really shouldnt matter becuase the output itself is deinteralced then converted to porgessive after the effects and slowmotion.

In the past, ive been able to slow down interlaced footage down to about 40% out to progressive scan and its been perfect.

this is something i cannot fathom im afraid
DJPadre wrote on 11/29/2007, 12:19 AM
bit f a workaround here, but it worked..

rendered the sequence out to DV AVI WS upper field first

wac that back into a progressive project..

bloody tedious and a waste of time, but at least it works..
farss wrote on 11/29/2007, 12:19 AM
Now you've got me thinking.

HDV is UFF, DV is LFF. I've only ever done the downconvert in Vegas and it comes out LFF naturally and although I've never tried doing any slomo on the footage I think I'd have noticed if the field order was swapped, especially on one project with lots of dancing.

However I remember authoring DVD for someone that we'd downconverted some footage for using a HDV VCR nad it did have some wierd stuff going on. He'd edited it in his old ULead system so I figured that was the problem but maybe not. The big question here could be why is the camera flagging the footage UFF not LFF.

Well I doubt we'll get an answer to that any time soon so maybe try changing the field order in Vegas, RClik the media and change the flag and see what happens. I know you're rendering to progressive but what happens depends on how you set thing up, Ithink.

If the project is interlaced then Vegas computes the FX in interlaced. Render to P and it de-interlaces the output of the FX chain, which will be interlaced and if the media has the field order flagged wrongly some wierd things could happen.

However if the project is progressive then the footage is de-interlaced before the FXs are applied and all should be OK.

Think I got this correct, sure worth a try and the symptoms fit the disease.

Bob.
DJPadre wrote on 11/29/2007, 12:40 AM
amendment to the above...

it works for teh majority of shots with static camera or reasonably stable handheld (actually im being modest.. lol)

where there are large elements of motions, such as a veil being removed over a brides head, it still stutters like an epileptic on speed...

not happy jan..
DJPadre wrote on 11/29/2007, 1:00 AM
jsut trying it with LFF then im off to a meeting and i be back to report any findings..
waht id normally breeze through has had me stuck for 3 hous in an attempt to smooth it out to no avail..
Coursedesign wrote on 11/29/2007, 1:35 AM
If you deinterlace before slowing the footage down, you lose a lot of movement information and get poor quality.

Additionally, Vegas doesn't have Optical Flow for generating true intermediate frames, which also makes things tougher here.

Is it the last major NLE not to have this?

DJPadre wrote on 11/29/2007, 4:50 AM
im not doign that though.. deinterlace comes last.. ..

BUT, as the source footage is DV AVI WS from an A1 downconverted, i have had to go through and change the Pixel aspect to 1.45 on each 16:9 clip as teh A1 doesnt flag the footage, or vidcap 6 flaked out during capture.. , whereas my DVX footage is fine...
So what im trying now is to see if this flakiness is ahppening because of the shift in PIA...

OK, jsut tested this theory... and render out squeeze to DV 4:3 Nada nothing zilch...
DJPadre wrote on 11/29/2007, 4:55 AM
now this is wierd..
its no happening to ALL the shots, only to afew of them.. moanly where the cammmera is a lil more shaky than normal.. but running it through Vdub was where i first noticed...

some shots its perfectly find and smooth, others.. its a write off
fldave wrote on 11/29/2007, 5:43 AM
Deinterlace Interpolate setting drops a field and works best for faster motion scenes, so I really wonder if you are getting 1 frame per field in slo mo.

Since you are working with downconverted DV, it should be lower field first, I think it is flagged wrong as UFF. You wouldn't notice it except for fast scenes.

Change the field order in the media pool of the original downconverted footage to LFF and see if the fast scenes clean up. If not, try to change the deinterlace method to Blend and None to see if it clears up.
DJPadre wrote on 11/29/2007, 5:58 AM
ive never downconverted incam before and as its sourced from HDV, i thought upper field first was a normal part of it..
if downconverted HDv is suposed to be LFF, then there is something seriously wrong somewhere...

would it be the flag in the stream (ie camera setting) or within vidcap 6?
fldave wrote on 11/29/2007, 6:10 AM
I have had periodic issues with a clip being tagged incorrectly as 4x3 when it should have been 16x9, but mostly with Virtual Dub loosing it. That was what made me think something tagged it incorrectly as UFF.

I don't do hardly any in-camera downconvert, just some testing about 18 months ago. I don't recall having any issues with my test footage. I have an FX1, and I think there may be a 4x3 camera menu option.

Right clicking the clip in the media pool should allow you to switch from UFF to LFF to see if that fixes it.

Laurence wrote on 11/29/2007, 6:11 AM
On many HDV cameras, there are three in-camera downconvert modes: one which squeezes the image into an anamorphic 16:9 SD image, one that letterboxes the image, and one that crops the side for a 4:3 image. My guess is that you chose the wrong one of these options as you captured. The correct one is the anamorphic 16:9 squeeze.
DJPadre wrote on 11/29/2007, 7:17 AM
thx fro teh replies,

PIA (pixel aspect ration, not pain in ass) was set to squeeze, no letterbox within cam.

As it turns out, the captured clips were flagged as 4:3, but the actual clips are indeed 16:9.
On top of that, the clips were also flagged as UFF.

Now, iev gone though and changed PIA to 16:9, and field order to lower, and the bugger works a treat.

The issue here then is why didnt Vegas pick up the DV codec (ie nuances within teh codec) as it should have?
The original files were captured in vidcap 6 and imported straight into a DV AVI project
fldave wrote on 11/29/2007, 7:50 AM
I'm always happy to hear that I'm right for a change, LOL! As I said before, it seems like most of my issues with this 4x3 - 16x9 wrong tagging is a result of Virtual Dub processing, but I could have had Vegas do it, too.

If you are sure that you didn't use Virtual Dub in between the capture and the file with the issue, just report it to Sony.

The moral of the story is if your aspect ratio is incorrect, the field order may be also and that should be checked.
farss wrote on 11/29/2007, 12:52 PM
I'll try and check but I think the problem is in the camera.
Vidcap certainly gets the 16x9 flag correctly off a DVCAM tape but I think in downconvert the VCRs and cameras don't send the flag.

Bob.
jrazz wrote on 11/29/2007, 1:22 PM
Which I would have looked at this earlier. I get the UFF issue most of the time when I downconvert incam. I always change it thinking it just flagged it wrong to LFF. I never thought it should be UFF. Don't know why, usually I assume I made the error.

Anyways, I use A1U's and again, I get this all the time when I downconvert incam and just as you found out, change the field order and the problem goes away.

j razz
DJPadre wrote on 11/29/2007, 4:37 PM
maybe this should be in the Vegas known issues... hmmmmmmm

coz i sure as hell wouldnt have known waht the issue was unless i ripped the guts out of it like we just did