Final Cut X Rendering with artefacts no matter what codec

[Robin S. kurz]

[Bret Williams] “Charlie never said that. “

Since you did not use any sort of QUOTE, which is always useful for avoiding misunderstandings, I could only assume you were addressing the OP.

[Andrei Popa]

Hi guys,

Thanks for the replies.

Robin

I think you did not read properly my initial post nor my reply. I said that the master file shows the artefacts.

Bret

If you look at it carefully there are artefacts, Charlie described it best as “kind of moving graininess” it’s more like lines / waves or waves of lines as opposed to the traditional square artefact.

These artefacts appear in the center about midway between the writing and the bottom of the screen.

It’s not so bad, but it shouldn’t be there, and if projected on a big screen it may look worse…

Charlie

That background is a generator that comes with Final Cut X. It does not have any blur function/control on it.

I find it very odd, because there shouldn’t be any problem at all, especially since it’s a built in generator, it’s not third party plug-in or a video file.

So my only explanation is FCPX is messing up…

Of course I’d prefer to fix it but I’m not sure it’s possible…

P.S. I watched it carefully inside FCPX after I wrote the above, and the artefacts are there as well, I don’t have any other effects plugins on this generator, so I guess it’s a FCPX mess-up…

Last but not least:

1. Is there any way to specify a fixed bitrate in FCPX or Compressor (fixed bitrate, not maximum bitrate limit)

2. This clip is about 7mbps at 720P

Is 12mbps at 720P make any difference on a big screen?

Theoretically it should, but if it’s crisp at 7mbps on your computer screen isn’t it going to be the same in the cinema?

The cinema screen will be way bigger, but the projector will still be putting out 720P…

[Bret Williams]

In compressor just use one pass CBR. 5000kb/sec should be fine for 720. But if the artifacts are there in the generator, then they’re going to be there on output. I’m really not seeing anything worth worrying about. But why not follow Charlie’s advice and add blur. You just add a blur filter to the generator. Gradients are the hardest thing for compressors to do. And it could look perfect in your file, but still break up with banding on another screen because it’s only an 8bit panel vs a 10bit panel. An off example, my iMac can’t tell the difference between 100% white and 110% white. It displays both as the same. But on my Flanders video monitor, they are significantly different shades. I’d say if anything, the projection of your project would be slightly less sharp than your computer screen .

[Andrei Popa]

It seems I haven’t read Charlie’s post correctly, he said I should add a blur and I understood I should remove it…

I tried it, and it doesn’t seem to do much, but it is a good idea…

Where can I find the one pass CBR setting in Compressor? I know it exists inside Adobe Media Encoder, but can’t find it in Compressor for .mov containers…

“the projection of your project would be slightly less sharp than your computer screen”

I guess a higher bitrate will make it sharper on the big screen…

[Walter Soyka]

The problem you are seeing is called banding.

Here’s a detailed explanation I wrote up for a related post some time ago in the Ae forum:

https://forums.creativecow.net/thread/2/1023784#1023815

Basically, as Bret was saying, the problem is that the tone difference is too subtle for your display to show. If you have have only 256 possible gray values (8-bit color), and you’re covering only a very small range of those 256 possible grays over a large area, you’ll get hard edges as the codec or display “clicks” over from a gray of say 200 into the next neighboring gray of 201.

You cannot blur your way out of banding; the line from 200 to 201 doesn’t go away, because your color depth is limited somewhere. Quite the opposite: you have to add a little bit of noise to dither or perceptually break up the hard edge. Decreasing the subtlety of the tone may also help if your design allows.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive   |   RenderBreak [blog]   |   Profile [LinkedIn]

[Andrei Popa]

Hey Walter,

Noise seems to work…

Thanks!

I love these things (technical quirks that you would never think about and are the exact opposite of what you’d expect)