This IS the Avid L2: Re: [Avid-L2] What happens under the hood between a progressive and interlace render?

Monday, December 14, 2015

Re: [Avid-L2] What happens under the hood between a progressive and interlace render?

"how is it possible to capture correct and clean 2:3 pulldown into the Avid while in progressive mode. The tapes were captured into Avid while the project was in 29.97P mode."

whoa. wait. this was captured as progressive? You may be screwed. I don't see how you can un-blend a progressive frame and remove the pulldown adequately. Or maybe you can, and Media Composer is smart enough to know that when you tell it after the fact that this piece of progressive media is actually interlaced, and to play it back odd lines then even lines, that it can split them apart. I'd have to test that. Otherwise, I've not been able to un-blend a frame.

On Mon, Dec 14, 2015 at 5:35 PM, bigfish@pacbell.net [Avid-L2] <Avid-L2@yahoogroups.com> wrote:

Yes the 1:1:1:2 or as I like to think about it 2:2:2:4 because of my fieldy nature seemed to me like the only proper way of doing things.

So here's my perception problem. An image is just a bunch of dots/pixels of various colors and shades that make up an image. These dots are the video essence. Whether they are packed as Psf/Interlace or true Progressive that dot pattern is still the same.

if in the image the first line is all white dots and the second line is black dots followed by a third line of white dots etc.... in a true progressive it would be a white line and then a black line and a white line etc... In a Psf/interlace structure the odd or even lines would be either black or white. Assuming the media is considered by Avid as progressive why would Avid feel the need to blend the white and the black lines when rendering in progressive format and not blend them when rendering in interlace mode? The proper image should still be a white line followed by a black line top to bottom. I can see where if the media was flagged as interlace that Avid would start to think it had to deinterlace but given in my case the media with 2:3 pulldown is flagged as progressive even though it is electronically interlaced why does Avid blend the Psf fields. It should just leave the white line white and the black line black. This is where I am not understanding the processing that is going on.

I understand the solutions of deinterlacing better now but what is really happening under the hood? If as you say the editor either considers something as interlace or progressive then how is it possible to capture correct and clean 2:3 pulldown into the Avid while in progressive mode. The tapes were captured into Avid while the project was in 29.97P mode. I know all the tape formats I deal with handle progressive media as Psf and that's what comes down the HDSDI signal into Avid. Why is it only when I render the safe color does Avid think it has to start blending things?

---In avid-l2@yahoogroups.com, <cutandcover@...> wrote :

What you're calling PsF is actually interlaced. Like I said, inside any editor, there is only progressive or interlaced. So you're saying PsF, but you really are looking at interlacing.

That said, the real way to handle getting 2:3 pulldown material to a 29.97p output is like this:

Open a 23.976p project
AMA the 2:3 pulldown (29.97i) file
drop into a sequence
Promote the motion adapter
Choose Film With 2:3 pulldown as source, progressive as output
detect pulldown
Mixdown.

If the source was constant cadence, you now have a true 23.976p source.

Open a 29.97p project
bring in the bin with the mixdown file
cut this into a sequence
default motion adapter should be progressive source, progressive output
Mixdown.
Output same-as-source.

Your resulting output is a 29.97p file with 1:1:1:2 pulldown. This is the best you can expect, but at least it won't be halved resolution or blended.

On Mon, Dec 14, 2015 at 4:37 PM, bigfish@... [Avid-L2] <Avid-L2@yahoogroups.com> wrote:

The reason I think Avid deals with the video essence in Psf fields is because if I toggle a 29.97 P project to 59.94i I can then step through the Psf fields in the Avid application. To me that means Avid is still structuring the data in a Psf manner. Every other line should be part an odd or even Psf field so why when rendered does it turn from a flutter typical split field to a jiggy jaggy. Perhaps it's the blending you mention but it's not like a timewarp where I can choose both fields, duplicates etc... Is that a preference in media creations that I can choose a global timewarp control? looked in media creations and see nothing. The Render setting has the choices for motion effect and timewarp but those don't seem to effect how the safe color effect gets rendered. It seems it's the blending that is causing the jiggy jaggies. Oh well I'll see how the network likes the first show. So far nothing has come back rejected. Moving forward I will just throw a duplicate field timewarp to deinterlace halving the resolution. Seems a shame to throw out all that stuff just for the web folks.

I'd think they would work out a workflow that knows how to encode 2:3 pulldown dynamically like the big hardware Teranex units will do. Just think of all the stock footage that has 2:3 pulldown why half it's resolution when proper software will handle the encode? It's like the actual broadcast viewer is less important than the online streming down the line. Seems like the priorities and the workflow could use some refinement.

Now if the Psf structure is just a transport mechanism then why does Avid think it needs to blend the two Psf fields to begin with? When I look at the field motion of the clip Avid has it flagged as progressive so why does Avid feel the need to blend the Psf information at all? Shouldn't it just be rendering the actual video essence and not "blending" the image data?

---In avid-l2@yahoogroups.com, <cutandcover@...> wrote :

What you say here:

"Given Avid deals with progressive material in a Psf manner"

is not true. Why would you think any editing software deals in PsF? PsF is ONLY a transport vehicle - any progressive item in any editing software or computer is always either progressive or interlaced.

So then you have to start at the beginning and think about what you're trying to do. You need to make a 29.97 progressive delivery. You have interlaced source. Therefore: deinterlace. Simple. You WILL lose half the resolution, that's the breaks. Not your fault - they're asking for it. There is NO WAY to preserve fields in a progressive delivery other than either blending or deinterlacing. And you already know what that blending looks like.

On Sun, Dec 13, 2015 at 1:49 AM, John Moore bigfish@... [Avid-L2] <Avid-L2@yahoogroups.com> wrote:

I posted a week or so ago about how I found on a 29.97P 1080 project when the source footage is 2:3 pulldown rendering an upper track of safe color limit while in progressive mode creates Jiggy Jaggy artifacts in the resulting render. Unrendered when parked on a split field I see the typical flutter of the split field frame but after rendering it's no longer a flutter but a baked in jiggy jaggy like interlace error but the lines of jiggy jaggy seem to be thicker than the single lines of interlace I would expect from a Psf field structure.

If I switch to a 59.94I 1080 project I can step through the fields/Psfs and both fields have jiggy jaggy interlacy issues. If I I render the safe color while in 59.94i 1080 then step through the fields of a split frame they are both clean like typical 2:3 pulldown. Given Avid deals with progressive material in a Psf manner why don't I still end up with two clean fields when rendered in progressive? Am I over simplifying the Psf structure under the hood? I would expect a render to merge the two fields independent of each other into a single progressive frame like I see before I render but these jiggy jaggies get baked into both Psfs.

The result is I have to render in interlace to avoid the jiggy jaggies but I realize any dve type moves or titles with animations will be rendered with interlace motion which is problematic for a true progressive project. Of course the show will air as interlace but the delivery spec is 29.97P I would assume the digital delivery department is where they will take issue to the 2:3 cadence. The simple option is to put duplicate field 100% timewarps on the 2:3 footage but I hate to half the resolution. Part of my brain says 2:3 is still progressive in the nature of the image but the other part says this isn't truly progressive either.

Curious what others think about this and why the jiggy jaggies get baked in to both Psfs.

John Moore Barking Trout Productions Studio City, CA bigfish@...