Can't not De-Interlace = QC Fail.

Hi All,

Trying to deliver an Interlaced project to a UK Network. Tech Specs require 50i.

Creating a 50i project in Resolve 17.2.1 (Enabling Field Processing in Master Settings),
See "Project Master Settings.png"

Project Master Settings.png (273.33 KiB) Viewed 1459 times

If I import a Interlaced clip, Resolve correctly identifies it.
Clip Attributes -> Field Dominance ->" Auto - Upper Field"

I can also manually select "Upper Field" and get the same result.

If I then drop the clip onto a timeline, Resolve appears to be automatically applying a De-Interlace filter to the clip. One easy way to verify this is by switching between the "Normal" and "DaVinci Neural Engine" DeInterlacing modes in Image Scaling. Even though there should be no de-interlacing at all, on my laptop, when "DaVinci Neural Engine" is selected, I can no longer play the sequence in real time.

Also, when I render to DNxHD 120i, if "Normal" is selected, I can render my project at around 500 fps, however, I can only render at approx 10 fps if "DaVinci Neural Engine" is selected.

In both of these cases, there is an Interlaced Project, with an Interlaced Clip, going to an Interlaced Output.
There should be NO De-Interlacing happening, however it's there, and there is apparently no way to turn it off. (No there is no De-Interlace Checkbox in Clip attributes). See "Clip Attributes.png"

Clip Attributes.png (359.02 KiB) Viewed 1459 times

Our current work around is to create a Progressive Project, and to Tag the Clips that we are importing as Progressive also, however, this method fails when we need to do blurs/ resizes etc.
Page 116 in the Resolve 17 manual somewhat addresses the limitations of this method.
NB - If the clips are tagged as Interlaced, in a progressive project, a De-Interlacing Filter is applied automatically, with no option to turn off (there's not even anything to advise this has happened).

So, as it stands, the only way to not de-Interlace interlaced footage in Resolve, is to incorrectly, label it as progressive, in a progressive project, however this method breaks if there are any zooms, translations, blurs, or other movement.

SURELY - There must be a way to work on an Interlaced Project, in actual Interlaced, without having Resolve attempting to De-Interlace. That's meant to be the whole point of enable Interlaced Video.

Please -if I'm wrong - can someone please tell me how to get around this!!

Thanks,

S>

You could just tell it to render 50i without interlace processing, no?
Are you seeing fields? Does your monitor support fields?
The de-interlace check box is called "Progressive", I think...

[Peter Chamberlain]

in interlace processing mode, with interlaced source clips, you can step field by field as is seen by the timecode display colon state.. what makes you think this is not interlaced?
When you render, and then review the clips in resolve or another test app, what makes you think they are not interlaced?

I'll try to explain in some more detail: if you define a timeline for interlace, your footage will get de-interlaced into the same number of frames as you have fields in the original. This way temporal resolution is preserved, while avoiding interlace artifacts from any process or filter that might change the position of pixels. You should see this in every movement when frame stepping through your footage.

On output you can decide if you want it re-interlaced or if you want progressive with twice the fps.

This approach makes sense, IMHO, but there's on thing missing: currently DR is not warning you if you don't cut on frame boundaries. This can introduce a weird kind of single-frame dissolves when re-interlaced.

in interlace processing mode, with interlaced source clips, you can step field by field as is seen by the timecode display colon state.. what makes you think this is not interlaced?
When you render, and then review the clips in resolve or another test app, what makes you think they are not interlaced?

Hi Peter,

Firstly, when my online editor contacted support regarding this issue, this is the response that they were given:

"In Resolve 16, if 'Interlaced Field Processing' is turned on, Resolve will not de-interlace a clip.

In Resolve 17 however, regardless of whether 'Interlaced Field Processing' is turned on or off, as long as a clip is identified as Interlaced by Resolve, in the Clip Attributes, Resolve will automatically de-interlace, and on preview you will see a deinterlaced version of that clip. Unless you change it to Progressive in the Clip Attributes."

NB - This is a direct, word for word copy of the exact message we received from support.
I thought that this was really weird - so I confirmed it.

Secondly, I was able to confirm that there is some kind of processing happening - in an interlaced project, with interlaced clips, by altering the type of interlacing, from "Normal" to "Neural" the performance on the system - both during playback, and whilst rendering to an interlaced output file is observably different.
This proves that there is some level of processing being performed by system.

The error that started this entire process was that we are getting shows rejected from QC repeatedly due to "deinterlaced footage".

NB - For the sake of transparency, I am in a different state from our online editor, and can't travel to her due to Covid restrictions, so I haven't been able to verify her entire project specifically.

However - I was CC'd on the support email - Point 1 above, I verified the processor slowdown when switching De-Interlacing types - Point 2 above.

We have been able to move forward by manually tagging all clips as progressive, and importing them into a progressive project. When the clip attributes are set to Progressive, and the Project is Progressive (i.e. Field Processing is not enabled) then changing the type of De-Interlacing has no effect on processing - proving that the de-interlacer is not in effect.

The disadvantage of this method is that it theoretically only works for "grades", i.e. Color and Contrast, and can not be used if there are any moves / zooms / blurs etc, as then when the master export (in progressive) is then changed to Interlaced, these shots have incorrect field dominance.

We currently are grading (only) in Resolve, and then Blur / Zoom / move etc back in Symphony.

Honestly, I would have expected that the Aus. support guys had given us incorrect information - re: permanently on de-interlacing - if I hadn't seen the performance hits that changing the de-interlacer was making - when it theoretically isn't even on.

Additional Info:

I've been doing some speed tests:

Progressive Project - Interlaced Clip - Interlacing Type set to "Neural Engine" - my clip renders in 44 seconds.
Interlaced Project - Interlaced Clip - Interlacing Type set to "Neural Engine" - my clip renders in 87 seconds.

From what I can tell, Uli is correct - Resolve seems to internally de-interlace to the Field Rate of the project.
i.e. 25 interlaced, becomes 50p internally, which is then converted back to either 25i or 25p on export.

This explains the performance hit, I'm just wondering if it explains why we are getting QC fails?

[Peter Chamberlain]

In 17, i believe we can process take interlaced fields and render interlaced fields without ever de-interlacing. That's the goal.. the internal way we do that is processing each field with and impact on speed as the system is optimized for frames.

Please ignore the support feedback for now, and don't try to make the interlace clip progressive.. lets just focus on putting interlace source clips, on a timeline, with interlace processing on, and rendering interlaced... and then play those renders back and see that they still are interlaced.

You can share a link to clips here if you would like others to verify too.

Did you make sure that your timeline is set with "Enable Interlace Processing" activated before you move any footage into it?
It's easy to miss this. And then, activate Interlaced rendering on output under Export video.

In 17, i believe we can process take interlaced fields and render interlaced fields without ever de-interlacing. That's the goal.. the internal way we do that is processing each field with and impact on speed as the system is optimized for frames.

Hi Peter,

After all that - I can confirm that Resolve 17.2.1 DOES pass interlaced frames correctly.

Testing Method:

Create a Resolve Project, set to Interlaced.
Import Camera Raw (EVS) files.
Export Camera Raw files as both DNxHD 120 interlaced 50.

Create a Avid 1080i50 project.
Import Camera Raw (EVS) files onto Video Layer 1.
Import DNxHD files onto Layer 2.
Apply a Difference Matte effect, to Video Layer 2 – which will show the difference between Video Layer 2, and Video Layer 1.
When stepping through the sequence, both frame by frame, and field by field, there is no difference between Video Later 1 and Video Layer 2.

Please accept my thanks and apologies. I was in a different state to the project that was failing QC, and it turns out that there was a comp incorporating mixed field material that was causing the failure, but the editor thought was a Resolve issue. The incorrect

I do have two thoughts/ comments though:

1. It would be ideal if Resolve either defaulted to moving in whole frames by default (like Media Composer does) or alternatively, made it difficult to apply cuts on incorrect fields. I agree with Uli that it is probably too easy to place a cut on an incorrect field.

2. Now we know that the De-Interlacer actually isn't doing anything when I only have interlaced clips in an interlaced project, I can't understand why having the quality set to "Neural" slows the system down so much.

Thanks for all your assistance,

S>