[Ardour-Users] Sycnhing audios?

Ken Restivo ken at restivo.org
Fri Jan 7 23:48:59 PST 2011

On Fri, Dec 24, 2010 at 06:55:52PM +0100, J?rn Nettingsmeier wrote:
> On 12/24/2010 06:34 PM, David Kastrup wrote:
> > 
> > Hi,
> > 
> > I have a camera which will also record short videos and has a builtin
> > microphone.  Of course with mediocre sound quality.
> > 
> > I also do a take of the same using ardour and good equipment.  Now what
> > I'd like to batch is to exchange the low quality audio with the good
> > quality one.
> > 
> > Another challenge is that just synchronizing the audio at the start of
> > the track is not enough since apparently the audio sampling rate of the
> > camera is not all too exact.
> that's all too common unfortunately.
> > So there is the combined task of correlating the audio tracks (the good
> > quality track is always longer since excess audio is easier to deal
> > with) and possibly using a slight time shift.  Or maybe at least get a
> > scale factor calculated with which one will shift the video since an
> > undisturbed audio seems more important.
> > 
> > Can ardour help with that task if I extract the lowfi audio from the
> > video and tell it "give me the exact correspondance from the high
> > quality audio"?
> the easiest solution is to record a click at the beginning and end, so
> that you have it both on the camera guide sound track and your decent
> equipment, and then use the time stretching tool to align the "good
> audio" to the clicks in the guide track.
> unfortunately, this will turn your good audio into bad audio :(
> so your best option is to process the video instead. throw away a frame
> here and there, or double one, as required. if you do it around cuts or
> when there's no movement, you can get away with it. robin gareus' xjadeo
> video player will sync to jack transport and help with the job.

I did this successfully some years ago. I used Ardour and a cheap Kodak digital camera. I put a "slate" at the beginning to sync the start of the audio and video. Then I imported the video's audio track into Ardour, wiggled the audio until it matched up with the video, then used the start point of the video as the start point for the Ardour audio track. Then I simply re-muxed the video together with the new audio track.

Results here:

and also somewhere on Vimeo, though I can't seem to find it right now.


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