Help! Artifacts with solid colors

[Mats]

Hi Everybody,
I hav used DOP back and forth for quite a while and it has always delivered fine results.
But now I have hit the wall with end credits that are text over solid red, pink or lila background.
The files are from photshop imported to Premiere exported as Prores 4444 to Resolve and the whole project exported as 4K scope prores 4444.
The end credits get vertical or horizontal banding (depending on color) and also blocking around text.
It gets better if I reduce saturation, add noise and gaussian Blur... I set bitrate to 200.
I did a 2K version (2k export from Resolve) and got the same problems. It is visible in DOP player, Easy DCP and Cineplayer.
Enclosed are three stills from the 2K version - taken from Resolve and cropped down to 500x500 pix in order to uppload.
Please help.
Thanks in advance!
Mats

[Carsten]

I think we had a similar issue a while ago, with animated graphics. Back then, I tested the footage with multiple different J2C encoders, and all showed the same issue. The only way to overcome this was to reduce saturation and/or use softening/antialiasing at high contrast edges. The outcome was that this seems to be a particular weakness in J2C.

Let me see if I can find it...

There it is, my brain is still working nicely...

viewtopic.php?f=2&t=248&hilit=Ringing


I would still try to rule out conversions prior to J2C encoding. ProRes is wavelet based just as J2C, and screenshots can be deceiving. Back then, I unwrapped the J2Cs from the generated mxf files and viewed them directly.

- Carsten

[Mats]

Thanks Carsten for you fast reply!

The pictures are not screen dumps - the are stills exported from resolve.
Resolve by the way plays back DCPs now without Easy DCP.
The artefacts looks like this when played back on a Dolby server and all the differ rent s/w player that I have.
I have of course already read the post you reffered to.

The best I can do so far is lowering saturation adding noise and then gaussian blur - but in order to remove the artefacts I get a very bland picture.

And I get the same vertical or horizontal banding when there is no text at all - so the sharp edges you are taking about really does not come into play. Actually where there is text there is a bit less banding.

'Do you think that the Prores 4444 pass might be a problem? I could export with another codec from Premiere.
I don't want to use another codec coming out of Resolve - Prores works so well in keeping levels going to DOP.

Can I send you something to analyse?

Thanks again for you help and isights!
Mats

[Carsten]

The banding I see is indeed a bit weird. If you have some raw footage/stills for me to test, I'd give it a try.

- Carsten

[Mats]

Thanks Carsten for your kind efforts,
The banding is what worries me - the artefacts around the text is expected and can be taken care of with some low pass, blur strategy.
Here is a link some short snippets before compression and the whole credits file:

I'm wondering if the two Prores 4444 passes is adding something?
I did a test with more noise and blur and reduced saturation and contrast but the banding is still there, although somewhat masked by the grain. But it does not look great.
Can you stitch J2K together so that I don't need to recompress the whole film?
Would it help to compress through Resolve instead - if it is DCI compliant now...
Im grateful for any help or insights.
Mats

[Carsten]

Wondering wether there is a Prores FFMPEG issue...

- Carsten

[Carsten]

Yes, you can stitch J2K in DCP-o-matic. Resolves DCP/MXF encoding is probably DCI compliant now - but I am not sure wether the discrete J2C format is.

Is this the full/commercial Resolve version?

- Carsten

[Carsten]

Hmm, wenn I export a single image from either Quicktime Player Pro or VLC snapshot (both uncompressed) of e.g. example_1.mov, I see considerable ringing. When viewed full frame on my laptop, I don't notice it, but, when I zoom in, it's there. However, this will not look nearly as bad on a cinema screen.

Bildschirmfoto 2018-11-03 um 23.58.31.png

I guess there are simply better codecs for this kind of work.

Will do some more tests, and try to replicate these stills in Photoshop and compress directly with DCP-o-matic.


- Carsten

[Mats]

Thanks again Carsten for you kind help!
My biggest problem is not the ringing but the banding - but none are good.
The original credits are animated in Photoshop, then bought into Premiere and exported as proves 4444 ant put into Resolve.
Im using the paid version of Resolve.
I have added the Photoshop files to the dropbox folder.
How do you stitch j2k in DOP?
Ideally for me I would code the credits and the film separate so that I don't hav to reencode the whole film. If I could stitch the J2K I could also max out the bitrate on the credits.
Mats

[Carsten]

You can e.g. create a feature-only DCP and just take that MXF and reuse it in DCP-o-matic - it will not be recompressed if the settings stay the same. Then just add the credits, in whatever format. DCP-o-matic will run through the main part, just copying, and then only compress the credits.

One would think that Prores4444 at high bitrates should look losless, but, it seems that some material is not suited to this. As these credits are short, you could try an uncompressed format. But I guess it will look similar after DCP compression. Don't try data rates beyond 235-240MBit/s, they will crash some playback servers, and it won't help anyway.

Maybe you can upload a very short passage in DCP (MXF only) format, so I can check it on our 4k projection system?

Can you try to explain (and maybe add a screenhot with a pointer) the 'banding' you see? Maybe also the J2C playback in Resolve is not optimized. Maybe they take shortcuts to enable realtime decoding?

- Carsten