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Gear / Technical Help => Post-Processing, Computer / Streaming / Internet Devices & Related Activity => Topic started by: JEMS on July 10, 2019, 08:00:49 PM
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I do a lot of transfers of analog reels and cassettes, many of which need pitch adjusting. I have yet to land on an ideal system to do these nor do the normal software programs I use seem ideally suited to pitch adjustments.
Has anyone got a workflow that they are happy with to correct audience recording pitch in the digital domain and how are you doing it?
Thanks in advance,
BK
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Steady state pitch adjustment that is constant throughout the recording, or wow and flutter type correction which varies over time?
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I've never paid for it, but Plangent Processes has the science down.
I guess if the original tape machine was not running right, you might still have the same pitch issue after Plangent, but I dunno...
https://www.plangentprocesses.com
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^ That's the top solution I'm aware of for wow and flutter correction, which is far greater challenge than steady pitch adjustment. AFAIK it senses variation of the recorded bias tone as the baseline for correction. It probably provides option for overall pitch adjustment as well.
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A non-varying pitch adjustment across the entire recording is much easier to achieve, and can be done in standard audio editing software.
In that case, the first thing to determine is if you want (or care if) tempo and run-time (is) altered along with the of pitch, which is computationally simple compared to holding tempo and run-time steady while altering pitch.
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Well aware of Plangent, but that's for real recordings. I'm talking about tape transfers of '70s and '80s audience tapes.
Not so much wow and flutter but adjusting each side for the vagaries of different tape decks and power supplies.
My question is really about how do you do it workflow wise (including what is the baseline for accurate pitch) and then is some software better than others for doing the changes.
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The "Kind of Blue" type correction, but for AUD tapes.
More tomorrow, heading out..
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FYI, TS member Heath is a professional transfer expert, perhaps he'll drop in here.
Regardless of whether it occured in the recorder or playback machine, if the pitch variance is constant and was caused by tape speed being off for whatever reason, then pitch and tempo should be adjusted together and the relationship between the two should remain locked. This is normal tape behaviour people will be familiar with- faster playback increases pitch and tempo and shortens playback time, slowing playback tape speed does the opposite. Lets assume that's the case.
A different scenario would be if all the instruments were mis-tuned (yet are in tune with each other) and that is what one wishes to correct. In that case one might not worry too much about the small change in tempo and run time want to adjust pitch while not changing tempo or runtime, in order to retain sync with video for example. This requires a more advanced tool, yet is available in many editors these days. Key words may be pitch-adjust, elastic-audio, etc.
First challenge is determining if the pitch/tempo is indeed incorrect.
Second is determining if it should be corrected or if it can be left alone.
Third is making the correction, if that is deemed appropriate.
How might one determine if it is incorrect?
Compare run time against alternate sources (marking identical start and end points)
Compare pitch against alternate sources (by ear, switching back and forth rapidly)
Determining if it needs to be be corrected may well be entirely subjective.
If using a varispeed tape machine for doing the transfer, the tape speed (and thus pitch) can be adjusted upon playback prior to digitalization. Otherwise, how specifically to make the correction will likely depend on the editing software you are using. Let us know that and folks using the same software can comment from experience. The "old school way" is to do a calculation, manually resample to a slightly higher or lower sample rate, and then playback the file at the standard rate.
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As to finding the "correct" pitch, if you know the key signature of the source material the best stab would be to sit down with a guitar or at a piano or keyboard and play along in the same key. You have to go on the assumption that the ensemble are at the correct pitch and not just relative pitch. If you have a second source of the original program you can make a 1:1 comparison, but even then you're making the assumption that the speed of the second recording was done at the same speed as the reproducing machine. Fuck, you could buy a pitch pipe for $3 and earball it of you know the key.
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Late to the party here, but a really nice way to deal with speed/pitch correction is to use Izotope...comes in super handy for certain transfers.
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Late to the party here, but a really nice way to deal with speed/pitch correction is to use Izotope...comes in super handy for certain transfers.
Can you elaborate? I'd love to know a simple workflow that you are following.
BK