What kind of noise is in this XC15 footage?

[Nick Mirro]

Hi. I'm testing a new XC15 and myself, being amateur. The clip is 4K30 422 8 bit in Wide DR. Frame rate was 30 and recorded directly to Inferno as prores 422.

The footage is played at 2x to emphasize movement, with the sound left at 1x.

This was shot on an overcast day (In the second scene foreground, there was trash. I did a pretty terrible job of hiding it using Davinci Resolve OFX patch replacer. Object remover was better but would not render).

The noise is very strong in the water at 4K. Is this aliasing? I've read that this camera's WDR and log will produce aliasing in post because of the 8 bit limit.

What would be the ideal method to improve this noise? Thank you much for any suggestions!

YouTube (Short URL)

[Bryan Worsley]

Could you provide a short sample (1-2 sec) of the original prores clip ? The first scene, that is.

[Nick Mirro]

Hi Bryan. Here is a dropbox link of the first 2 secs. Had to finally learn basic ffmpeg to cut it, and glad I did!

https://www.dropbox.com/s/0m139a3u48...slice.mov?dl=0

The ... on the far right has the download link.

[Bryan Worsley]

OK thanks, I'll look at it later this evening.

Edit: Looked at the sample. Sure this is Wide DR ? If so, looks like there was a levels mix-up up at some point. Here imported into Resolve at "Video Levels"

https://i.imgur.com/EKQ37ev.png

Anyhow, taken as is, some quick levels adjustments:

https://i.imgur.com/8KZGcPw.png

You said it was an overcast day so I didn't brighten it too much. Lifted the shadows a bit. Only very minor tweaks to the color balance.

Your UHD YouTube video (UHD vp9.mkv download))

https://i.imgur.com/pi0aqOi.png

As regards "The noise is very strong in the water at 4K". For sure there is noise in the areas of shade along the river bank. Is that what you are referring to?

https://i.imgur.com/wQ9Ai0I.png

[Nick Mirro]

Thanks for looking into this! How did you find the youtube vid? It wasn't listed and usually takes me a minute to locate it. :D

No adjustments were made and it was for sure shot in Wide DR. It was recorded directly from the XC15 hdmi to a Ninja Inferno.

Here is the youtube clip link.

YouTube (Short URL)

Look at the red leaf on the lower right in the foreground. The one that sticks out into the scene. It is pointing to open water that has tons of what I understand to be mosquito noise.

The same noise is also visible on the water surface in the second part. I think it is a compression artifact related to aliasing.

https://en.wikipedia.org/wiki/Compre...Mosquito_noise

So I am planning to mess with Davinci Resolve noise filters and motion blur, though I have never done it before. I thought the noise would look blaringly obvious as it does to me. Maybe I've been staring at it too long.

[Bryan Worsley]

Originally Posted by Nick Mirro

Thanks for looking into this! How did you find the youtube vid? It wasn't listed and usually takes me a minute to locate it. :D

It's there in your first post. I used 4K Video Downloader to download the 4K VP9.mkv file and converted to Cineform for importing into Resolve.

Originally Posted by Nick Mirro

No adjustments were made and it was for sure shot in Wide DR. It was recorded directly from the XC15 hdmi to a Ninja Inferno.

Well it looks like it got compressed somehow - when you cut the sample with FFMPEG maybe ? What command line did you use ?

I would have suggested using VirtualDub2 - just load the video file, set your cut points and output 'Direct Stream Copy':

https://sourceforge.net/projects/vdfiltermod/

Originally Posted by Nick Mirro

Look at the red leaf on the lower right in the foreground. The one that sticks out into the scene. It is pointing to open water that has tons of what I understand to be mosquito noise.

The same noise is also visible on the water surface in the second part. I think it is a compression artifact related to aliasing.

I don't see mosquito noise around the leaf - please post an enlarged/cropped image. I do see some feint 'ringing' (halos) on high contrast edges/fine detail (twigs etc) which is a by-product of the in-camera sharpening - and Wide DR is more susceptible to it.

Originally Posted by Nick Mirro

Maybe I've been staring at it too long.

Maybe ! You sound a bit like me. Whenever I get a new camera I go hunting for problems ;>)

[Nick Mirro]

Originally Posted by Bryan Worsley

Well it looks like it got compressed somehow - when you cut the sample with FFMPEG maybe ? What command line did you use ?

ffmpeg -i xc15_s001_s004_t012.mov -ss 0 -t 5 -c copy slice.mov

Neither the XF400 and XC15 shoots raw. I was told there is some low level compression that happens even when outputting to hdmi. It makes sense since recorders do not see the input as raw. So maybe that is the compression you were suggesting.

Originally Posted by Bryan Worsley

I would have suggested using VirtualDub2 - just load the video file, set your cut points and output 'Direct Stream Copy':

Nice tip. Just installed it.

Originally Posted by Bryan Worsley

I don't see mosquito noise around the leaf - please post an enlarged/cropped image. I do see some feint 'ringing' (halos) on high contrast edges/fine detail (twigs etc) which is a by-product of the in-camera sharpening - and Wide DR is more susceptible to it.

Not around the leaf. In the water more than a leaf length in the direction the leaf is pointing.

Originally Posted by Bryan Worsley

Maybe ! You sound a bit like me. Whenever I get a new camera I go hunting for problems ;>)

Think you're right. No one else who saw this clip pointed it out.

[Bryan Worsley]

Originally Posted by Bryan Worsley

I don't see mosquito noise around the leaf - please post an enlarged/cropped image

Originally Posted by Nick Mirro

Not around the leaf. In the water more than a leaf length in the direction the leaf is pointing.

Here's a crop of that area, taken from the 2 sec prores clip you provided:

https://i.imgur.com/FL2OM1R.png

What are you referring to specifically? Mark it on the image.

[Nick Mirro]

https://postimg.cc/BP8cXLQ3

It shows during playback since I think it is motion induced noise.

[Bryan Worsley]

Ah OK. I'd put that down to aliasing when downscaled on an HD display, but viewing on a 4K TV with Roku player it's there in the original prores clip, converted to x264. Really busy this weekend, but I'll look into it further, unless someone else has an opinion meanwhile. I don't own an XC15.

[Paul R Johnson]

I'm very confused. It simply looks like low res material. It doesn't even look like 720? There's some noise sure, but it's just so soft? The big sections of the water are not even as good as SD. Something very strange has happened.

I dug up some old DV material and this has a similar appearance but this is 4:3 cropped so quite low res

Beach Test - NPM-702 Shotgun Microphone on Vimeo

One is SD one is 4K? really?

[Nick Mirro]

Are you referring to the pasted screenshot or the actual footage?

[Nick Mirro]

Originally Posted by Bryan Worsley

Ah OK. I'd put that down to aliasing when downscaled on an HD display, but viewing on a 4K TV with Roku player it's there in the original prores clip, converted to x264. Really busy this weekend, but I'll look into it further, unless someone else has an opinion meanwhile. I don't own an XC15.

I'll try playing it back through a 4K projector, the only 4K display we have. Thanks much Bryan!

[Paul R Johnson]

The YouTube video just looks really unlike 4K footage - that's what I meant. The sharpness, the definition the colour rendition all seem wrong. We're used to the mangling YouTube does to the video, but this seems excessive. We often talk about the tiny differences in what lenses do to 4K, good or bad, but this just looks, well, wrong?

[Bryan Worsley]

Yeah, something is not right and the levels in the Prores sample (Slice) definitely got compressed:

Here's the original sample again, imported into Resolve at 'Video' levels:

https://i.imgur.com/EKQ37ev.png

Here I brought the Prores sample into VirtualDub2 with the 'Decode Format' interpretation set to 'Limited' (Video) range (16-235), exported to Prores HQ at 'Full' range (0-255) and brought the export into Resolve at 'Video' levels again:

https://i.imgur.com/Ja4iPsS.png

Now IMHO that (based on my experience with Wide DR on a Canon HF-G40) is how Wide DR should look on an overcast day. So it appears there was a 'Limited-to-Full range' switch at some point resulting in compression of the luma range.

Then a simple matter of bringing up the Gain to brighten, with some minor tweaks to the color balance:

https://i.imgur.com/sBQOuES.jpg

Or pushing the Gain further, with highlight pull-down ('HL' tool) to avoid clipping:

https://i.imgur.com/VfPIztz.png

No need to bring down the black point as you do with your original sample.

I know this doesn't answer your question about the 'noise on the water' but it suggests that something went awry with your Inferno recording over HDMI; unfortunately I have no experience with Atomos recorders.