• Apple Final Cut Pro Legacy

  Compresser shortens dur after 44.1kHz Wav to 48kHz Aiff conversion

  Posted by Si Ryan on February 14, 2008 at 11:54 pm

  Hi ya there. Created a droplet with compressor to batch convert audio files from 44.1 kHz to 48kHz AIFF files. It shortens/clips the duration of the track by about 8% ( 100 second clip comes out as 92 seconds). I created another droplet which produces an audio only Quicktime movie and it works perfectly (using the same bit depth/KHz settings), durations are correct and final cut plays them fine. Can anyone see a problem using this method?

  Cheers
  Simon

  P.S The droplet is heaps easier than using ITUNES or quicktime player to convert… so thats why I want to go that way! All my files go where I want, quickly too.

  P.P.S Is this a known Compressor issue? I’m relatively new to using it.

  When in doubt, ASK!

  Si Ryan replied 18 years, 6 months ago 3 Members · 3 Replies
• 3 Replies

• 

  Bret Williams

  February 15, 2008 at 3:30 am

  There really is no reason to convert files to 48k anywhere but within the FCP timeline itself. Doing so can actually cause more grief as you’re discovering. Many folks still recommend it out of habit I suppose, bit you can do the conversion directly in the timeline since version 4. Place the audio file (which can actually be the file copied off a cd) directly in the project and timeline. If Fcp’s ability to convert it on the fly isn’t good enough for you, then, simply do an item level audio render on the file. This actually upconverts the file to the seq setting, and then uses the resulting rendered file as a proxy. You can adjust volume, add filters, add layers, move it around, whatever and it won’t unrender. It’s ecactly the same process as concerting in compressor or iTunes, eccept it still retains the link to the original, which converting in a different app will not.
• 

  Andreas Kiel

  February 15, 2008 at 5:04 pm

  Bret is right.
  Some additions below.

  As far as I know Compressor won’t do a real resampling on this file (at least with the standard settings) but just replaces parts of the header – means 44100 will be replaced by 48000.
  This will give you a 8.125% speed up with an additional file which is the same as the original but has a different header and therefore speed.
  Think of the sampling of an audio file like the FPS of a video – if you change the rate of 30 fps of it to 60 fps it will run twice as fast as the original. If you apply a filter to resample pictures to get the double amount of pictures FPS will still stay the same but it runs twice as long.
  So with audio you have to use an app to interpolate the “missing” samples and to merge both of the above – keeping “FPS” at the same level and calc the “missing” frames. FCP can do that as Bret described.

  Regards
  Andreas

  Spherico
  https://www.spherico.com/filmtools
• 

  Si Ryan

  February 19, 2008 at 9:15 am

  Thanks Bret and Andreas for your posts. Tried and it works. Well done. Unfortunately, with our FCP 6.01 (can’t update yet) dropping renders regularly, plus not wanting to risk any issues exporting OMFI files for Audio-Post work, I feel safer keeping to the pre-import conversion method.
  However… do you by chance deliver OMFI files for audio mixing? Just looking for some security before I change old habits!
  Cheers
  Si

  When in doubt, ASK!

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