0 Replies Latest reply on Feb 8, 2011 10:20 AM by OneOfTheseWillBeAvailable

    "Monitor 2" external device frame rate conversion

    OneOfTheseWillBeAvailable

      Hi,

       

      When I set "External Device" to "Monitor 2" in the playback settings options of the sequence settings dialog, Premiere obviously has to do some sort of conversion to display the timeline, which is not at 60fps, on a 60Hz display.

       

      How does Premiere do this? Do we have any control over it?

       

      When I play back my 25fps footage in VLC, VirtualDub or Quicktime, there is a very slight stammer in motion, as the 25fps video updates a 60Hz displayand the amount of real time for which each frame is displayed varies. I consider this normal.

       

      However, when I play back my 25fps footage in Premiere, it looks terrible, choppy and lacking in fluidity, much worse than the subtle stammer visible in other software. It's so bad that nontechnical people have walked up to me and asked what's wrong with it. This problem does not exist with 30fps footage, where the frame rate is more evenly divisible into the display refresh rate, which confirms this is not a disk speed issue.

       

      But - as I say, it doesn't look nearly so bad in other software which must be dealing with exactly the same issue.

       

      There are controls for 24p pulldown to 60, but no control over how 25 is handled.

       

      Can someone advise on what the approach is supposed to be here?

       

      Thanks,

       

      Phil

       

      PS: Premiere lists this monitor as being at 59.00fps, which I think is wrong, because the graphics driver tells me it's at 60, but I suspect that isn't at the core of the issue.

       

      PPS: An appendix on what I think is happening. In most video software, playback is actually timed to the audio, and the video image updates as and when it needs to. Except in the case of a hardware device (such as a Blackmagic card) which has locked audio and video clocks, the video (graphics card) and audio (sound card) devices are not locked together. So, with a 30fps timeline on a 60Hz display, you will usually see exactly two monitor refreshes per frame, but you will very occasionally get either one or three refreshes for a frame, depending on which device is comparatively slowest. This is normal practise for video software. Does Premiere do it like this? I presume that's all it can possibly be doing, but it is certainly doing something different to what VLC, VirtualDub and Quicktime do because it looks much worse than they do.