3 Replies Latest reply: Nov 25, 2013 11:59 PM by _durin_ RSS

    Audio Sync Drift in CC with two 48khz tracks

    Alex LK Community Member

      I am having a major problem getting two tracks to sync up.  Im on deadline and am freaking out since nothing seems to work.

       

      I have two tracks recorded in 48khz that I imported from Premiere. One is from an onboard shotgun camera mic. The other is a wireless lav mic, and two ambient mics recorded as one track into a Zoom H4n.  When I import them into Audition, the first thing I do is manually align them in the multitrack editor using a loud handclap in the recording. However, drift occurs and towards the end there is a slight, but noticeable echoe. 

       

      I've also tried using the Automatic Speech Alignment tool, but it processes to 37% and then Audition freezes up telling me that my system is out of memory. Im on a late 2012 Retina display Macbook Pro with a solid state drive and 8 gigs of RAM, so that certainly may be the case.

       

      However, I feel like I shouldn't even have to get to this point with the Automatic Speech Alignment tool crashing Audition, since the tracks are the same sample rate and I have a audible marker to align them by.

       

      Does anyone have any suggestions? I'm really at a loss.

        • 1. Re: Audio Sync Drift in CC with two 48khz tracks
          _durin_ Employee Hosts

          Speech Alignment will not be the right tool for this.  It's designed for alignment of short passages of re-recorded material is it performs warp and stretching. 

           

          Do you have the same issue if you use the multicam audio sync tools in Premiere? 

          Are you splitting the channels in Premiere or in Audition, and if you're splitting them in Audition, are they synchronized prior to being extracted to separate files?

          Are the files of the exact same duration?  If one is slightly longer or shorter than the other/video, you may want to enable Clip Stretching and just slightly stretch the shorter clip to match - it should snap to the length of the other clips.  Check the alignment in Real-Time mode, then flip it over to Rendered for better quality output.

          • 2. Re: Audio Sync Drift in CC with two 48khz tracks
            Alex LK Community Member

            Thanks, Durin.  I'm not splitting either track into channels, although the Zoom at least is recorded in stereo. Not sure if the camera mic is mono or stereo.   The recording on the Zoom is actually a few seconds shorter since it was located in a different part of the room and I had to walk over to it, so maybe I should try Clip Stretching, but really this seems to be more of an issue with Audition I think. I also have PluralEyes3.  It sync up the camera audio and the Zoom audio great, but when I bring that sequence in Premiere, it seems to leave the Zoom audio behind....

            • 3. Re: Audio Sync Drift in CC with two 48khz tracks
              _durin_ Employee Hosts

              Ah, I misunderstood your original post.  So you have the camera audio and the zoom audio file.  The reason for the drift is there is no shared clock.  The sample rate of most devices fluctuates a tiny bit which becomes apparent over time, as you've experienced.  A clip stretch may get it better synchronized, as would re-interpreting the sample rate.  But this is a problem PluralEyes and Premiere's Multicam Sync are better designed to solve.