7 Replies Latest reply on Aug 29, 2011 2:01 PM by Jim_Simon

    GPU Acceleration Confusion

    ExactImage Level 3

      I've asked about the effects of using a GPU in other threads and, if I read things correctly, was told that GPU would have no real effect on exports to MPEG2 formats, except where there is resizing involved, or to speed up the rendering of effects, but not help at all in the MPEG2 encoding.  Fair enough.




      Today we built our first Windows 7 PC with GPU for use with Premiere Pro.  While perhaps not the fastest beast in the world, it's an i7 (2600) with 16GB ram and some fast hard disks.   We also added an nVidia 570 graphics card.


      There were a couple of tests that surprised me, given the advice in previous threads.   Here is one example:


      1) Delete all render files


      2) A 26 minute sequence (1920x1080) with ProRes 422 footage took (or would take) 1 hour 11 mins to export to MPEG2 Blu-ray with no effects applied.


      3) Delete all render files


      4) Add a simple three way colour corrector, with NO adjustments and re-export the same sequence and it took only 26 minutes.


      Repeat the above steps at will, showing that it's not files in a cache or anything else that's causing the speed increase.


      So, if the GPU does not assist with MPEG2 encoding, why does adding a Three Way Colour Corrector (with NO adjustments), which presumably triggers the GPU in some way or other, suddenly speed this process up?   Surely it would have slowed things down, if anything.


      What am I missing?