6 Replies Latest reply on Oct 17, 2018 11:57 PM by gw009

    Strange video levels when scaling

    Qframe

      Hi there,

       

      Has anyone experienced strange sub 0% video level 'noise' I suppose you could call it, in video that has been scaled?

       

      For example while working in a SD timeline, if you import a HD clip and scale it using Scale in the motion tap,  the Lumetri scopes show that the waveform gets pulled apart and some of the 'black' elements are dragged down below 0%, some as low as -20%. The application of a the Video Limiter has no effect in correcting the levels.  While dragging the time bar the levels move back up then re-appear when stopped.  I thought it might just be a monitoring issue but if the timeline is exported the level issue remains in the exported clip (import back in to test). Obviously you need to have 'Clamp Signal' unchecked on the scopes to see it.

       

      Even when down-converting on export (Media Encoder) the levels are messed up.  Basically if video is been resized the levels are effected.

       

      Hopefully the following images will demonstrate the problem. The first image shows an 'unscaled' clip.  The waveform is normal (blacks a little low for broadcast). The second image shoes the same video frame scaled down to an arbitrary size of 90%.  You can now see that the levels are extending down and some movement in the rests of the image wave form.  Third image is a CU of the waveform.

       

      Prem_Level_Test-100.jpg !@@

       

      Prem_Level_Test-90.jpg

       

      Prem_Level_Test-CU.jpg

      Hopefully someone can shed some light on this problem. Up until now we were using Premiere for broadcast work but this issue creates 'illegal' video levels for broadcast. We have used DiVinci Resolve to re-correct the levels but it is putting another conversion in workflow. We have other editing software on the machine that don't suffer from this problem.

       

      Currently we are using an iMac with High Sierra OS and the latest Prem Pro version.  The same problem occurs on our brand new Macbook Pro with latest software so it seems that it's a Premiere problem.