audio / clock drift

[Julian Lang]

definitely more info needed. what is the format in which each was recorded? WAV, AIFF, MOV and any number of possibilities. Was it in 44.1 or 48 Hz? Bit depth? What are the makes of the machines on which audio was recorded?  

jl
 
Julian Lang
P.O. Box 2276
McKinleyville, CA 95501




Institute of Native Knowledge
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<www.instituteofnativeknowledge.com>


On Friday, September 19, 2014 6:29 PM, Doug Whalen <whalen at haskins.yale.edu> wrote:
 


  Dear Lindsay,
  It seems likely that your video recorder was not digital; hopefully the audio recorder was.  If so, do the following:  Open the two audio files in Praat.  Get the (exact) ratio of the from-audio wav file to the from-video wav file (dur_from_audio/dur_from_video).  Select the from-video sound object.  From the Convert menu, choose "Lengthen (overlap-add)".  This will use the PSOLA algorithm to change the duration but maintain the original F0.  Put your ratio in the "Factor" field and click OK.  This should create a new sound object with the same duration as the from-audio file.  Check to make sure it all seems right.  
  Don't forget to save the new sound object!  It's not a file until you save it.
  Hope this works, Doug DhW



On Sep 15, 2014, at 4:16 PM, Lindsay Marean <lmarean at bensay.org> wrote:

I'm hoping that someone here on ILAT has run into this problem and can suggest a way to deal with it:
>
>We're recording fluent speakers talking, with both audio recorders and video recorders.  Recently I recorded a session in which an audio recorder picked up one speaker really well, and a video recorder picked up another speaker really well.  I can use Audacity to combine the audio (one on each stereo channel) into a single WAV file that I can then use with ELAN for transcription.
>
>The problem is that the two recorders don't record at exactly the same speed.  In a long session, this difference becomes very noticeable - the two tracks may be perfectly synchronized at the beginning, but they will be out of sync by the end.
>
>Here are a few things I've found on the Internet that I think discuss the same issue: http://www.acoustica.com/mixcraft/v4/help/hs1550.htm and http://forum.audacityteam.org/viewtopic.php?f=46&t=75868.
>
>I've been trying to use the change tempo function of Audacity to adjust one track, but it's been trial-and-error - change by a small value, see if it works, and then when it doesn't, undo the change, and change by a different small value.  So far my approach is really time-consuming but still not really successful for making a transcribable track.
>
>Has anyone else dealt with this problem?  How?  Does anyone know of a better way to get both tracks moving at the same speed, beginning to end?
>
>Thank you!
>Lindsay Marean
>



Douglas H. Whalen, President 
Endangered Language Fund 
300 George St., Suite 900 
New Haven, CT 06511 
USA 
+1-203-865-6163, ext. 265 (or 234 for Whalen) 
elf at endangeredlanguagefund.org 
 www.endangeredlanguagefund.org
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