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Time Shift = Phase Distortion
Working on the latest Mac Avid…
I have talent voice on two tracks. I used a little Time Shift to speed up parts of it Sounded fine through playback. But when exported, the areas that were timeshifted had all sorts of distortion and volume oscillation which I attribute to some sort of Phase issue.
Same with some Stereo music I brought in. I sped the music up a hair. Sounds fine when the Audio Output tool is set to stereo. But when I switch it to a mono (mixed) output it has the same phase issue. And when I export same thing.
Has anyone else experienced this problem? Is there a solution for time shifting stereo tracks”?
TAK
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4 Replies
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Could be rounding errors.
If it’s just a bit, i would pitch shift. You also get a speed change, but the quality remains exactly the same, at the cost of a pitch shift.
Up to a few percent no-one will know. (Speeding up 24 film to 25 pal normally is pitch shifted, this is 4% and no-one complains)Bouke
https://www.videotoolshed.com/
smart tools for video pros -
Pitch/Speed corrections are among the hardest things to do. Indeed, you may end up with minor phasing errors, that show up even harder when you listen to a mixdown (multichannel to stereo or stereo to mono).
One thing that is key is that you need to run the plugins in multichannel mode, and that you need to process them as being stereo tracks. Otherwise, you will have two unrelated calculations, one per track, and that would increase the risk of phasing issues.
Unlike Bouke and many others I dislike unintentional pitch changes. I agree with him that a speed change with an unchanged pitch is much more tricky to accomplish than a speed change with a changed pitch.
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I’ve run into this same problem on occasion with voice tracks. Since voice is typically really just dual track mono, i.e. the same voice on both tracks, I typically find it easier to to pitch change just one of the source tracks and then put that on both tracks of my timeline. Actually in my case, on 60 MINUTES, for our studio material, we spread voice over left, right and full level center track, so for this purpose, I do the pitch change on the center track and then spread that result out to left and right.
M. Scott Cole
Senior Post Production Editor
60 MINUTES
CBS News, NYC
sc6@cbsnews.com
mscottc@comcast.net -
Thanks for the responses… I try to avoid pitch shift since I am intercutting the altered voice with the original unaltered.
I will experiment with some of the solutions. The easiest seems to be working from one track. Of course I lose my stereo in the music.
TAK
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