9 Replies Latest reply on Aug 6, 2013 8:33 PM by fgpikus

    Premiere Pro CC a/v sync: perfect in timeline, bad after export

    fgpikus

      I have a problem with exporting video from Premiere Pro CC. My project looks like this: there are 3 video tracks (3 cameras, Sony TM700K and two Canon EOS DSLRs) and two extra audio tracks (Tascam and Zoom recorders). In Premiere, everything is perfectly in sync. I had to stretch the rate of the recorders by a small fraction (few seconds of stretch per hour of recording) but after that all five audio tracks (three cameras and two recorders) are in perfect sync. In the final version, I mute the camera tracks and use the recorder tracks (camera tracks were handy for aligning everything to precise sync). I play the video in Premiere, everything sounds perfect. I export H.264 or DVD MPEG2 and, toward the end, sound is badly out of sync.

       

      Here are the things I tried:

      1) Delete all media cache files - ho change

      2) Unmute one camerate track and export: the camera track is in sync but the recorder track is not, now I hear "echo" in exported video.

      3) Export short fragment at the end of the video (I thought that may be it gradually loses sync) - the exported fragment is out of sync

       

      Overall, it behaves as if my rate stretch was not applied correctly to the WAV files from the recorders, but this only shows up in exported files, Premiere itself plays stretched WAV files exactly right.

       

      Anyone knows what the problem is and how to fix it?

       

      Thanks,

       

      Fedor Pikus

        • 1. Re: Premiere Pro CC a/v sync: perfect in timeline, bad after export
          Jim_Simon Level 8

          Have you tested with a burned DVD?

          • 2. Re: Premiere Pro CC a/v sync: perfect in timeline, bad after export
            fgpikus Level 1

            No, I tried to multiplex the DVD file, and it shows the same problem as the H.264 file (and the audio delay is exactly the same).

            The only way that I know to create a burned DVD from Premiere CC is to feed the DVD-MPEG into Encore CS6. I can try, but I don't see how Encore can fix the audio delay between different tracks (if I unmute the camera audio and the recorder audio, I hear the "echo", it's baked into one WAV file at that point, how would burning a DVD help?)

            • 3. Re: Premiere Pro CC a/v sync: perfect in timeline, bad after export
              Jim_Simon Level 8

              Not sure it will. It's just a standard test when things go wrong - you don't trust media players or computers, you put it on a disk.

              • 4. Re: Premiere Pro CC a/v sync: perfect in timeline, bad after export
                fgpikus Level 1

                Oh, I see what you mean: you think that the sync is broken by the media player, not the export.

                This is what I thought at first too, that's why I did the test with the camera sound track: now I get a single exported WAV file with two audio tracks mixed, and I hear these two tracks with about one-second delay between them.

                • 5. Re: Premiere Pro CC a/v sync: perfect in timeline, bad after export
                  Jim_Simon Level 8

                  I really got nothing on this for an explanation, once the problem is confirmed.

                   

                  How did you slow down the Zoom/Tascam clips?

                  • 6. Re: Premiere Pro CC a/v sync: perfect in timeline, bad after export
                    fgpikus Level 1

                    Using the "Rate Stretch" tool on the end of the clip in the timeline. I used the TM700K recording as the "primary timeline" to which all other tracks were synced (it has a 5.1 audio track). Zoom and Tascam WAV files are on their own stereo audio tracks. I drag the WAV clips so the beginning of all sound tracks is syncronized. Then I go to the end of the recording, find some sound I can sync on, and use the rate stretch tool to drag the end of the WAV clip. I actually had to speed them up a bit (compress the clips), and on export they seem to revert to their original duration/speed (or at least mostly revert). Once I align the end of the WAV clips so I get perfect sync at the end, I go to few random places in the middle to see if I have a sync there, and I do.

                    I thought that may be the 5.1 track has something to do with it, so I tried sending it to a stereo submix first (WAV clip tracks from recorders are going directly to Master). This had no effect on the output.

                     

                    How would I confirm the problem? I can easily generate a clip with out-of-sync audio, or a clip with delay between TM700K and Tascam tracks. But how would I show that it was in perfect sync in Premiere? I can do analog capture of it playing through speakers...

                    • 7. Re: Premiere Pro CC a/v sync: perfect in timeline, bad after export
                      Jim_Simon Level 8

                      Using the "Rate Stretch" tool

                       

                      Maybe try undoing that and right clicking the tracks instead, changing the 'speed' manually.  This has always worked for me when the audio recorder doesn't keep correct time.

                      • 8. Re: Premiere Pro CC a/v sync: perfect in timeline, bad after export
                        fgpikus Level 1

                        I think I see the problem: When I right-click and select "Speed", I can set it to 100.01% or 100.02%. One is too fast, the other is too slow. The rate tool lets me stretch at almost arbitrary precision, BUT... when it renders, it appears to snap the speed to either 100.01% or 100.02%. If I right-click on the rate-stretched track, I can see that "speed" is 100.01%, but I know this is not exactly true: If I start from the unmodified WAV and set speed to 100.01%, I see that the waveforms don't exactly line up toward the end (and I can hear the difference). So it would appear that I need speed of something like 100.014% but I can't really get it, and the rate tool gives me an illusion of such precision but at export time snaps to 0.01% grid.

                        Ok, so I know what the problem is. Now, what can I do about it?

                        • 9. Re: Premiere Pro CC a/v sync: perfect in timeline, bad after export
                          fgpikus Level 1

                          I tried editing "duration" instead of "speed" and here is what I find: I can set "duration" to any value up to 1/30th of a second, and the waveforms shift accordingly, and the preview in Premiere changes to match. But if I right-click again and see what "duration" is, it's not what I set. For example, I can set duration to 52;06;20. Look again, and it's 52;06;28. Ok, I type in 52;06.28 and the waveforms shift slightly. I type in 52;06;21, check again - still 52;06;28. The next lowest value I can get to stick is 52;06;19.

                           

                          The odd thing is, Premiere timeline appears to reflect what I typed in, i.e. there is a difference between 52;06;28 and 52;06;20. But exported audio is the same in both cases, as is the value I see in "duration" after I check it again.