Thin grey dashes (artefacts) after Compressor encode?

[Harry Powell]

Hi Dave. The frame rates are the same for both, i.e. 25 fps.

[Harry Powell]

Thanks Dave for your Slug idea. It seemed so intuitively good, that I’m surprised it didn’t work though.

I’ve retraced my steps with a new test, and can confirm that these lines don’t appear when (in Frame Controls) Resize Filter and Deinterlace are both set to Fast rather than Best. They DO appear when Resize filter is set to Best and Deinterlace is on Better, as they do when both are set to Better.

I’m running another test with both on Best just to see if that clears it, but it’s not really practical to use those settings as it takes so long .. (as discussed in recent thread)

[Harry Powell]

UPDATE –

Setting both Resize Filter and Deinterlace to Best does seem to get rid of those lines, but this is impractical to use as it would take about 20 hours to encode a ten minute video!

I also tried Fast settings for both, but text then looks awful, even with a high data-rate (6000kbps) and even on static text.

And as I mention on the compression forum, cropping the lower edge in Compressor doesn’t remove it either ..

Any more thoughts anyone?

[Harry Powell]

oh and I should also add … this was a problem on FCS2 as well as FCS3 which I’ve only just moved to ..

[Brad Elliott]

One thing you could try as a last resort

Create a 720p sequence with required specs and put your 1080 sequence in and render for 720p.

[Harry Powell]

Thanks Brad for suggestion, but isn’t that the same (or perhaps worse) than keeping Frame Controls in Compressor on Fast settings – which removes problem but reduces picture quality? You did get me thinking about isolating this problem though …

I really need to solve this! Am I the only one having this problem?

I did a test in Compressor where I tried to change just 1080i to 1080p, i.e. ProRes to ProRes, left Frame controls Resize filter on Fast (as it wasn’t changing), Deinterlace setting on Better, and Adaptive Details ticked. It didn’t solve the problem…

I managed to hide the problem by adding a 6 pixel black strip to the lower frame edge, i.e. Output Image ‘Padding’. In full screen this isn’t really noticeable .. as long as your monitor/TV frame is black! But if not watched in full-screen and your background isn’t black .. it is very noticeable!

Also, it’s very strange it took a 6 pixel crop to hide the glitch, because the original fault itself looks nowhere near that deep. I tried 2 pixels then 4, and it seemed to be moving up with the crop. The I noticed a 5 pixel crop almost covered it and the 6 pixel crop definitely covered it!

Now .. if no one can suggest what’s causing the problem and how to solve it(?) .. could someone please talk me through exactly what settings I should have in the Compressor Geometry settings so that instead of having 6 pixels of ‘Output Image inset (Padding)’, i.e. a thin black line on the bottom frame edge, I have instead a slightly vertically stretched Output Images so that 6-pixel-deep mask is effectively removed? Whatever I’ve tried (and I’ve tried a lot) isn’t working.

I hope all that makes sense! If not, I’ll try and make amends ..

[Harry Powell]

UPDATE – In case it’s helpful to anyone(?) … I think I found a solution!

Basically I use Compressor twice. Once to just deinterlace the ProRes 1080i ProRes footage, and then I take the resulting ProRes 1080p file and run that through Compressor a second time to crop 2 pixels from the source bottom, re-scale to 1080, and encode to H.264 (1080 or 720).

But is there any quality loss in this method?

One advantage of this (other than removing those artefacts on the bottom frame!) is that using Best settings in Frame Control is now a viable option, i.e. it works a lot quicker in this 2 step method. On my set-up, a 10 minute video takes about 4 hours rather than 24 hours to encode.

HOWEVER … I now have a NEW unwelcome artefacts problem! On Best Frame Control settings, on white scrolling credits on a dark background, I’m getting white sparkles around the text! It’s very noticeable, and as this is not a Disney production, quite inappropriate.

What could be causing that and how do I get rid of them?

[Brad Elliott]

Harry,

We use a Kona LHe card and many of our “this shouldn’t work or be the best way scenarios” have been solved by putting our source in a final output sequence and rendering. This is not an absolute but we have had more success than failure. I would be curious to see what your sequence looks like in FC if it was put in a 1080p sequence and then exported to 720p via Compressor or QT.

Most of the files that we run through Compressor never have the frame controls set above the default and everything looks great. Better and best have solved some problems but not always. Most things that we create with Compressor look awesome but I have found it can be consistently inconsistent with some tasks.

Another possible solution for the bottom of the frame issue:
Nest the sequence and open in the viewer and change the scaling in the motion tab to 101 or 102(do not go over 105) and reposition accordingly so you do not have to crop/distort your image. It isn’t ideal but I would choose this over Compressor cropping my image or just cropping the bottom vs. bottom and top.