Subject:Speed Correction

Posted by: oblio98

Date:9/15/2009 3:23:25 PM

Suppose I record the audio from a reel to reel tape into Sound Forge 10 and later find that the speed fine-tuning on the Reel to Reel was a little faster than it should have been. I now have the wav file on the PC, but it needs to be speed corrected.

It's not really "Time Stretch", and it's not really pitch correction. What tool in Sound Forge is best for getting the wav file to the proper speed?

Subject:RE: Speed Correction

Reply by: Steven Myers

Date:9/15/2009 4:35:45 PM

Yes, it really is time stretch. It really is pitch shift.
If correctly adjusting the deck's fine-tuning and starting over is not an option:
I have not yet tried the élastique Timestretch tool, so I'd start with that -- if for no other reason than to see how I like it.

Subject:RE: Speed Correction

Reply by: oblio98

Date:9/15/2009 4:48:49 PM

Well, I understood "Time Stretch" to be a way to strech a piece of audio over a greater period of time WITHOUT changing the pitch, and "Pitch Correction" to be changing the pitch WITHOUT lengthening the time.

To do speed correction, you would want to change the pitch AND the time, like turning the pitch control on a turntable or reel to reel, which is different than SF's Pitch tweaker which does not legnthen the time.

Maybe I'm wrong? It would not be the first time! <g>

Subject:RE: Speed Correction

Reply by: Steven Myers

Date:9/15/2009 5:02:25 PM

If you would actually look at the timestretch tools, you would see that they generally allow you to keep the pitch as it is or adjust in proportion to whatever you do with the speed.
If pitch is your concern, you get the choice to simultaneously adjust duration. Or not.
BTW, the Sony plugs do give you those options.

Subject:RE: Speed Correction

Reply by: Chienworks

Date:9/15/2009 7:36:33 PM

What i'd do is figure out the ratio of the change you need. If the tape played 2% fast, divide the sample rate by that ratio. If you're using 44.1KHz then you'd get 43235. Double-click the sample rate display underneath the waveform and type in this new value. Sound Forge now thinks the file was recorded at that bitrate and will play it correspondingly slower. Go to Process/resample and resample it back to 44100 to keep the new slower speed at the right sample rate. Make sure you set the quality slider all the way to the right to get the best resample quality with the fewest artifacts.

Subject:RE: Speed Correction

Reply by: Steven Myers

Date:9/16/2009 4:02:24 AM

Double-click the sample rate display underneath the waveform

Thanks, I didn't know that!

Subject:RE: Speed Correction

Reply by: rraud

Date:9/16/2009 8:32:24 AM

If I know the song was recorded without any detuning (A-440 for instance) I connect my strobe tuner to an output, set to the song's key and bump the sample rate up/down, like with a tape machine's pitch control. A sustained chord works best.