DNxHD posterization/banding? Also, applying a look in metafuze?

[Jamie Havill]

Hi,

We're transcoding 4K (2:1 at 25fps) footage to DNxHD 175 (10 bit) 1080p out of Metafuze for our offline editor and experiencing banding. I'm using full debayering quality and OLPF is set to high. It's not a major issue, but I just wondered if this was normal? I was under the impression DNxHD 175 was used for conforming in some cases?

Lastly, is it possible to apply a 'look' through Redcine/Redcine-X to Metafuze with a PC only based workflow?

Thanks in advance.

[Job ter Burg]

Hard to comment on the banding without seeing the image in question. Also: are you sure it's not a monitoring issue? You might be working in 10bit while looking at an 8-bit monitor?

As for applying "looks", that would be done by creating RLX files in a Red application (I used to do it in RedAlert), then apply those RLX files to the transcodes in MetaFuze (bottom of the setting pane).

[Jamie Havill]

Thanks Job. The banding isn't a major issue, it isn't present in the R3D, or the Prores 422 I just exported, but it is in the DNxHD. I'm not too bothered, as these files are only for offline.

I'll try and create an RLX and import it into Metafuze. Last thing, we shot 2:1, am I correct in selecting 'Letterbox (center)' for conversion mode to preserve the correct aspect ratio and prevent the image from being stretched?

Jamie.

[Fredrik Harreschou]

DNxHD 175 is 8 bit. DNxHD 175x is 10 bit. The 8 bit version can easily introduce banding...

[Jamie Havill]

Hi Fredrik,

In Metafuze I'm selecting 'DNxHD 175 (10 bit)' so can only presume this is DNxHD 175x. It's more a curiousity than problem as to why the banding exists. Have you ever experienced banding using DNxHD 175x?

[Fredrik Harreschou]

As far as I remember, no...

[Michael Lindsay]

Red acquired footage often creates banding in certain pipelines... DNxHD at 10bit is still pretty compressed. When onlineing on a Avid you can use 16bit Tiffs to get better quality but you can still produce banding if you push the footage a lot... Working this way also stops you using metafuze.

I suspect (but don't know) that DNxHD filters a little in the shadows pre-encode. This pulls out micro detail (mostly noise) and subtle gradients band...

Michael L

[Job ter Burg]

we shot 2:1, am I correct in selecting 'Letterbox (center)' for conversion mode to preserve the correct aspect ratio and prevent the image from being stretched?

Yes.
(I wish this were the default setting)

[Sean Carley]

Yes, in a recent Red to DNxHD 175X project we did get banding in certain shots, especially where there was a very shallow depth of field. We found the only way to really mitigate it was to export our R3D files from Redcine. Metafuze and Red Alert gave us more banding (this was pre-Redcine-X by a month or two). The files converted using Redcine were much better and for the odd shot that had banding we dealt with individually.

[Michael Lindsay]

What file format did you export from Redcine as?

thanks

M