6 Replies Latest reply on Dec 5, 2008 3:31 PM by Jim_Simon

    CD Audio Drifts Out of Sync

    blazer003
      Ok, I know this is a known problem as long ago I read something on this, but for the life of me can't remember.

      I have a CD with all audio recorded from the sound board from a wedding (They had ambient mics and lapels for the preacher and the bride and groom)

      I shot the video with just the on board mics which are decent shotguns.

      I captured the footage and ripped the audio off the CD, and lined them up in Premiere. At the start it's fine, but as it goes along it gets progressively out of sync. The audio gets further and further ahead. Now, after 1 hour of footage it's only out of sync about 2 frames. Enough to cause a noticeable echo.

      So 2 questions:

      It would seem I could use time correction on the audio to change it ever so slightly to match, but will that degrade audio quality?

      Otherwise, is there another solution?
        • 1. Re: CD Audio Drifts Out of Sync
          Harm Millaard Level 7
          No, no AFAIK.
          • 2. Re: CD Audio Drifts Out of Sync
            Jim_Simon Level 8
            No to both questions. It's what I do myself.
            • 3. Re: CD Audio Drifts Out of Sync
              Level 1
              Boy, that was helpful, huh, Matt?

              There may be a better way but my suggestion is this: Pick a point at which the "out of syncness" becomes noticeable; make a small audio edit only and take out a few frames of ambient sound. You can do this as many times as you like (or you have time for) and by the end of the video, it should be less annoying.
              • 4. Re: CD Audio Drifts Out of Sync
                Jim_Simon Level 8
                It should also be a hell of a lot more work. Speeding up the CD track by a few hundreths of a percent (mine comes out to 100.04%, Matt will have to experiment with his) won't affect audio quality and will sync the entire track in one shot.
                • 5. Re: CD Audio Drifts Out of Sync
                  Colin Brougham Level 6
                  I've never had to do anything as long as a wedding, as far as syncing CD audio--just dance performances that are usually less than 5 minutes, so I don't notice any drift. I don't know if this will work or not, but it might be worthwhile trying to resample the CD audio (which is 44.1kHz) to 48kHz.

                  Use your CD ripper of choice (CDex, for example) to extract the audio to a PCM WAV file, and open that up in your preferred audio editor (Audition, Soundbooth, Audacity, or whatever). Save the file back to a PCM WAV file, but set the sample rate to 48kHz. Import that file into PPro and replace the original version, then check for "unsyncing". As I said, I'm not sure if that'll work, but it's worth a shot.
                  • 6. Re: CD Audio Drifts Out of Sync
                    Jim_Simon Level 8
                    >it might be worthwhile trying to resample the CD audio (which is 44.1kHz) to 48kHz

                    If done correctly, the resampling should not have any impact on the length of the track, only the top end of the frequency range. It'll go from 22 KHz to 24KHz, which no one is likely to notice. So this technique will also likely be a waste of time.

                    To reiterate, adjusting the speed of the CD track by the amounts required will have no audible impact on sound quality, and is the best method to achieve sync in this case.