4 Replies Latest reply on Jan 24, 2012 7:53 AM by Glitchdog

    Export issue (appearance of 'dead pixels' in the exported file when using Maximum Bit Depth setting)


      After having searched the forum for an answer to my question and not finding it, I have decided to add it in a new post to this forum.



      I come from using Final Cut Pro 7 and find Premiere Pro to be a pleasant change to my editing experience. I like the interface and the fact that there is no need to render anything in the timeline to be able to play the footage with some effects or corrections applied (even if it should be at lower quality). I have been using an early 2009 17-inch Macbook Pro (Core Duo 2.66 processor and 4GB of RAM) to edit AVCHD footage that has first been transcoded to ProRes LT. The footage is on an external hard drive connected to my Mac with FireWire 800. Although of course my platform is far from being optimal, it is fine to edit my footage as a hobby and it has been fine to edit using both Final Cut Pro or Premiere Pro.



      My first issue with Premiere Pro came when I exported my finished footage. Whether I exported the footage as an H.264 file with smaller resolution for the web or as a 1080p ProRes LT QuickTime file, I noticed ‘pixelation’ (or is it ‘posterization’?) in the out of focus areas of the image. While I understood that this was perhaps normal in a file that had been exported for the web, I was surprised to see this effect on the 1080p ProRes LT QuickTime files. This ‘pixelation’ was not nearly as strong in the preview window in Premiere, but would appear in the exported 1080p ProRes LT QuickTime file. In the export settings, I would always use the “render at maximum quality” setting (and I would always leave the “Use Preview Files” setting unchecked). I became concerned about this since I did not remember encountering a similar issue in Final Cut Pro 7, and eventually tried to run some comparative tests based on the same footage in the two softwares. This confirmed that Final Cut Pro exported a ‘clean’ and near-identical image to that in the preview window in Final Cut Pro, while the same footage exported also exported as an 1080p ProRes LT QuickTime file would introduce this posterization effect in the final file.



      I thought I must have been doing something wrong in my exports in Premiere Pro, as I just could not believe that such difference would be possible. And indeed, after much tweaking, I discovered that by selecting “Maximum Bit Depth” and “48-bit” in the export settings of Premiere Pro, this would effectively produce a much cleaner and close-to-the-original 1080p file. I also used the same “Maximum Bit Depth” setting on H.264, smaller-sized (720p) exports for the web, and to my relief the ‘pixelation’ or ‘posterization’ of the less-detailed parts of the image pretty much disappeared and looked near-identical to the results I could obtain from an export from Final Cut Pro.



      However, upon further inspection, I noticed that these exported files to which I had applied the “Maximum Bit Depth” setting had a new issue. Some frames now have what I could best describe as a ‘dead pixel’: white, pixel-sized dots, appear for just a frame in a random part of the image. It could be just one instance every 10 seconds, but sometimes it could result in more, such as a few of these white pixels in just a second of exported footage. I have tried various different footage, with or without color correction or other effects, and the result is the same: using the “Maximum Bit Depth” setting in the export produces a very clean, good quality image, but introduces this most peculiar artifact of ‘dead pixels’.



      I have spent a couple of weeks trying many different settings in the export window to find a way to fix this, but cannot find where it is coming from. Obviously, the original AVCHD or ProRes LT footage does not have such ‘dead pixels’ – they are created at the export process. One other thing that I noticed: if I set the maximum bit depth setting in the sequence render settings themselves (i.e., not at the export, but while I edit), this artifact appears in the preview window of Premiere Pro!


      I have also done a clean re-install of the softwares after a full formatting of my internal hard drive, hoping that perhaps this was a result of some software conflict caused by months of clutter on the internal hard drive, but this did not change anything.



      Has anyone ever encountered this issue before or knows what could be the source? If I cannot solve this, I will probably have to go back to using Final Cut Pro 7, as I have not encountered any such issue with that software before, and I need to obtain a clean, good quality HD file on export. Posterization is perhaps not such a big issue for a file that will end up on the web, but for use at home I need very good quality. It would be a pity to have to go back to Final Cut Pro just because of this issue, especially since Premiere Pro is clearly a winner on most fronts!