19 Replies Latest reply: Jul 25, 2014 8:42 AM by JSS1138 RSS

    Frame Rate Bug

    JSS1138 Community Member

      I think I've stumbled upon a bug and could use some verification.

       

      In short, I cannot get any Adobe software to correctly output 24fps media to same.

       

      The longer version is that I've got some 24 fps media at exactly 24, not 23.976.  Premiere Pro reads the media correctly at 24.  (Though on a side note, both Media Browser and Prelude read it incorrectly as 23.98.)

       

      I've created a matching sequence and exported that one clip (no edits, no effects) using both Queue to AME and direct Export from PP.  I've also tried the Render Queue out of AE for the same clip in a matching composition.  I've also tried Ingest in Prelude with a Transcode.

       

      I've tried exporting to DNxHD, UT, MPEG2-DVD, H.264, H.264 Blu-ray, and JPEG image sequence.  The export specs match the 24 fps for all formats.

       

      This was tested on both Windows 7 and Windows 8.1.

       

      In every single case, brining that exported media back in and placing it directly over the original, the frames to not match.  The audio is perfectly in sync, the durations are correct down to the frame.  But as I move through the footage, the frames begin to mismatch, so that if I click the eyeball to turn off track 2 and see the original underneath, it's a different frame!  They start off identical, and they end up syncing again near the end so there's no duration discrepancy.  But the frames in between do not match!?!?!?

       

      This does not happen with my 23.976 media, only with the 24 fps media.  It does seem to take some time for the drift to pronounce, like 5 to 10 minutes of media.  It didn't show up on shorter clips.

       

      The clip tested was spanned into two files, so I wonder if that plays a part.

       

      Can anyone with genuine 24 fps media test this?  It's a pretty serious bug if such media will not export frame accurate.

        • 1. Re: Frame Rate Bug
          shooternz Community Member

          Exactly what media (camera footage / codec) are you using in your test?

           

          I am guessing maybe your hacked GHx ?

           

          Haved you tried anything else?

          Whats the issue if...

           

          The audio is perfectly in sync, the durations are correct down to the frame.

          They start off identical, and they end up syncing again near the end so there's no duration discrepancy.  But the frames in between do not match.  WTF!

           

          Sounds like a GOP preview  type of thing .

          • 2. Re: Frame Rate Bug
            JSS1138 Community Member

            It is from a hacked GH2.  It's the only camera I have access to that can record genuine 24 fps.  All the others do the faux 23.976, which does not produce the error.  I need someone with RED, Alexa, BMCC or other such 'high end' cameras who might have some 24 fps footage to test with.

             

            The footage is I-frame only, so GOPs do not play a part.

            • 3. Re: Frame Rate Bug
              Steven L. Gotz Community Member

              My camera won't produce 24fps, just 23.976 so unless you have a short 24fps clip you can let us use for the test, I suppose exporting something from After Effects is the next best bet.

              • 4. Re: Frame Rate Bug
                Steven L. Gotz Community Member

                I interpreted some 23.976 as 24fps in Ae and exported it to 24fps. Premiere Pro sees it as 24fps.

                 

                I repeated the 9 second clip over and over to achieve a 20 minute sequence which I am exporting to H.264 now. When it is finished, I will bring it back into Premiere and see how they line up.

                 

                If they are identical, you will need to provide footage or find someone who has some. But if this test shows a discrepency, then Adobe will have an easy way to replicate the problem.

                • 5. Re: Frame Rate Bug
                  Steven L. Gotz Community Member

                  My test failed to replicate the issue.

                   

                  So, footage produced in After Effects comes out 24fps according to Premiere Pro and exporting it and bringing it back in revealed no issues.

                   

                  So there must be something about your footage.

                  • 6. Re: Frame Rate Bug
                    JSS1138 Community Member

                    It's quite possible.  But the test would be more accurate using one long clip, instead of repeating the same clip over and over.  As stated, shorter clips do not seem to produce the issue.

                    • 7. Re: Frame Rate Bug
                      Steven L. Gotz Community Member

                      Well, if you want to post one that shows the problem, I don't mind downloading it to help out. I just don't have a way to shoot 24fps exactly. Not that I know of, anyway.

                      • 8. Re: Frame Rate Bug
                        JSS1138 Community Member

                        Thanks, Steven.  Let me shoot some stuff I can share.

                        • 9. Re: Frame Rate Bug
                          Steven L. Gotz Community Member

                          Jim,

                           

                          Set up your camera pointed at a digital clock.

                           

                          Run 20 minutes or so.

                           

                          That ought to make comparing frames a lot easier.

                          • 10. Re: Frame Rate Bug
                            JSS1138 Community Member

                            Good call.

                            • 11. Re: Frame Rate Bug
                              shooternz Community Member

                              Only if it has parts of a second on the clock.

                               

                              A stopwatch would be better.

                              • 12. Re: Frame Rate Bug
                                Steven L. Gotz Community Member

                                I would be willing to bet that there are stop watches on the Internet that you could point a camera at. Good idea Craig.

                                • 13. Re: Frame Rate Bug
                                  shooternz Community Member

                                  Smart phones have them.

                                  • 14. Re: Frame Rate Bug
                                    joe bloe premiere Community Member

                                    Dum phones don't (mine).

                                     

                                    Online Stopwatch

                                    http://www.online-stopwatch.com/full-screen-stopwatch/

                                    • 15. Re: Frame Rate Bug
                                      Mark Mapes Employee Hosts

                                      Back in my days working on OnLocation, I often tested timecode-related matters by shooting footage of both  a stopwatch and a mirror showing the camera's LCD flipped forward, with the timecode on.

                                      Not particularly relevant to this thread, but when I was checking for dropped frames nothing beat shooting a pendulum like this.

                                      And my favorite trick for testing audio sync: snapping clothespin  in front of the camera every few minutes. On playback, there was no mistaking the frame when it snapped and the spike in the audio. When retrieving the C47 from wherever it flew became tiresome, I even rigged one up with a short strand of monofilament that I'd loop around my finger.

                                      • 16. Re: Frame Rate Bug
                                        JSS1138 Community Member

                                        Some more data:

                                         

                                        I shot a stopwatch and tested.

                                         

                                        https://dl.dropboxusercontent.com/u/106505510/24%20FPS%20Test.zip

                                         

                                        What I found was that the export was largely correct, except for the last few frames.  The error was PP not reading the file correctly for display in the sequence.  Every now and then, PP would repeat and/or skip a frame.  This repeat/skip is what was throwing off the match between original and export.  Ironically, the export seemed to be frame perfect, except for the last few frames, which PP had to fudge in order to get the 'correct' duration.  I put correct in quotes because the original was actually 4 frames longer than it should have been due to the repeated frames.

                                         

                                        So the question becomes, why is PP reading the file correctly for export, but not for display in editing?  That's messed up!

                                        • 17. Re: Frame Rate Bug
                                          Steven L. Gotz Community Member

                                          Could it simply be a long GOP issue? That the preview is screwing it up? Have you tried changing your preview file codec? Does that codec even matter if you don't render?

                                           

                                          Sorry. More questions and no answers.

                                          • 18. Re: Frame Rate Bug
                                            JSS1138 Community Member

                                            The footage is I-frame only, so no GOPs.  Preview codec wouldn't matter without creating a preview file.  Though since the export seems to be frame accurate, I wonder how a preview would turn out...

                                             

                                            I did find that even a three minute clip produced the issue, so if anyone out there has real 24 fps footage, I'd love some confirmation on this.  At this point I don't know if the problem is my footage, or PP's handling of all 24 fps footage.

                                            • 19. Re: Frame Rate Bug
                                              JSS1138 Community Member

                                              I seem to have been the only one with this issue, but just in case another reader happens along, the CC 2014 version does NOT have the issue.  24 fps media from the hacked GH2 works correctly.