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

Tuesday, December 15, 2015

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

This is what I've been talking about. If I switch to 59.94 I see perfect 2:3 pulldown when field stepping. When I'm in 29.97P I see split frames as the typical wobble. But when I render the upper track safe color limit while in 29.97P the split frames become jiggy jaggy or blendy wierd with interlace like artifacts and when I toggle back to 59.94 and field step through that render now both fields have jiggy jaggie artifacts and I no longer see clean 2:3 pulldown. If I monitor below the safe color render the perfect 2:3 cadence is viewable in field step.

If I render the safe color effect while in 59.94 the 2:3 cadence is maintained and the Psf/fields are clean. So something is blending or something when rendering in 29.97P.

When you say the 25P will show interlace artifacts when you ingest 50I is it a wobble or are both fields clean if you toggle to 50I and do the clean fields become jiggy jaggie if you render the 50I footage while in 25P? I think you will see the difference I'm seeing if you do that. I don't know if it's unique to the safe color on an upper track render but I'd doubt it.

From what I see it seems Avid does some blending or whatever to combine the two Psf/fields when rendering in 29.97P which mucks up each of the subsequent render Psf/fields if viewed in 59.94 and field stepping. It also makes for ugly frames when viewed in 29.97P. It's like baked in interlace error but seem more extreme than just the interlace offset. It's almost like it over compensates when blending the interlace fields and creates an more pronounced interlacy offset than actually exists between the two fields.

So for whatever reason Avid will ingest over HDSDI a 59.94 source with 2:3 pulldown while in 29.97P mode and the resulting video essence inside Avid will have two clean discrete Psf/fields viewable in 59.94 as clean 2:3 pulldown. So avid doesn't detect that it's a 59.94 source on ingest and it doesn't balk at the capture.

---In avid-l2@yahoogroups.com, <Job_L2@...> wrote :

> On 15 dec. 2015, at 00:49, bigfish@... [Avid-L2] <Avid-L2@yahoogroups.com> wrote:
>
> leads me to believe Avid still thinks of these things as Psf/Interlace under the hood.

Incorrect. It doesn't really care.

What happens is that it stores 1920x1080 pixel frames. Whether these are originally two 1920x540 fields or not is just a question of how it will be played back. It is stored in the same way.

Easier to think of in 25fps, since it skips pulldown cadances.

So for instance if you capture a 50i signal into a 25p project, MC will flag the result as progressive, and play it back that way (causing interlace artifacts). If you then flip the project to 50i, you can still field step through the original 50 fields.

If you capture a 25p source into a 50i project, MC will flag the result as interlaced, and play it back that way (essentialy dividing every frame into two fields). If you then flip the project to 25p, it will no longer do the field divide, and show both fields simultaneously (showing the actual progressive frame)

So I wonder what happens if you flip your project to 59.94i. What do you see then if you field step through the footage?