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Weird Pitch Bending in very old Audio File for Restoration

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Weird Pitch Bending in very old Audio File for Restoration

Postby oberob2020 » Sun Feb 02, 2020 9:47 pm

I've been handed this old audio track (over 30 years old) for restoration. There is this weird pitch bending at some point that I can't seem to fix. I tried using adobe audition pitch bending plugin to reverse it but the bending already applied to it changes so fast at one point that I can't seem to reverse it. Any ideas what might help with the task?

Here is a small sample: https://www.mediafire.com/file/8tjndcve ... d.wav/file
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby Tim Gillett » Mon Feb 03, 2020 4:51 am

The pitch variation is normally called "wow" and was a common problem with analogue recordings made or played back on faulty equipment. Do you know what was the source format? Is this a video sound track? Does the entire recording have this fault or only a part of it?

There are some steady high frequency tones in the programme. The highest tone of about 15.5 kHz might have been been suitable as a pitch reference for correction but it doesn't seem to change in pitch itself, so I doubt it would be of any use.

My first thought is that it's a poorly transferred (or recorded) analogue recording. If that's the case it would probably save a lot of problems to have the source recording (if available) re transferred.
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby James Perrett » Mon Feb 03, 2020 3:05 pm

It sounds like there is some background music and, as far as I can tell, it doesn't seem to change pitch when the voice changes (but I could be wrong).

This sort of effect could be caused by a tape reel catching on something and being slowed down during recording - or by a cassette with poor mechanics.

The best tool for this sort of thing is probably Celemony's Capstan but I understand that Cedar also has something similar. There is a pitch tool in Izotope's RX7 which is improved compared to RX6 but it is still very primitive compared to the standard of other tools in RX7.
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby oberob2020 » Mon Feb 03, 2020 4:29 pm

Thanks to both for the quick and helpful replies :)

To answer the questions:

Tim Gillett

1) I do not know the exact source format. It was recorded in a professional studio using analogue equipment in 1985. All backups available at the studio including the master tapes have the same issue. It was just mixed (carelessly) like that.
2) Yes, it's a video soundtrack.
3) There are over 20 hours in the recording but this particular issue is only present in those 10 seconds.

James Perrett

1) You are absolutely right - the background music is fine. It's the voiceover that was recorded with the issue and mixed with the track.

I will try your suggestions. Thanks a lot.
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby Tim Gillett » Mon Feb 03, 2020 9:08 pm

Thanks for the extra info. I wasn't sure whether the fluctuations were in just the voice or also in the music. I hear a steadier tone, a little like a trumpet playing a B and then an A flat. It has a wobble in it but not sure if that was intended. Possibly only the speech track had the problem. Our ears generally tolerate a lot more fluctuation in speech than music.

I understand Celemony Capstan does not work on speech alone.

The Plangent Process (developed by Jamie Howarth) works on any content but it needs an objective time base reference, normally the ultrasonic bias tone recorded on the magnetic tape. With Plangent that ultrasonic tone needs to be captured from the tape itself which can mean special playback equipment and technique. The bias tone can not always be recovered though, such as if the tone did not carry over from the original voiceover track to the mixdown.

As James says it may have been caused by a tape slowing down, probably the mixdown tape. That has the opposite effect in playback. The voice actually speeds up, as it seems to here. On that assumption you could try only slowing down the sections of the speech that sound too fast/high pitched. Don't try and lower speed and pitch separately. Lower both together.

Failing that, is it possible that in the 20 hours of good soundtrack the same or similar few words can be extracted and assembled to replace the short damaged voiceover section? With Izotope's Music Rebalance you could perhaps try to isolate the musical elements from the speech elements giving you more options to reconstruct the short section.

Another option sometimes used with older films/videos where part of the voice tracks are damaged or missing is to have voice actors re read the lines, sometimes the original actors if they are still around.
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby James Perrett » Mon Feb 03, 2020 10:07 pm

oberob2020 wrote:1) You are absolutely right - the background music is fine. It's the voiceover that was recorded with the issue and mixed with the track.

In which case, unless you can find the original voice recording tape with no music you are unlikely to be able to create a realistic end product. Any automated system will be looking for shifts in the whole spectrum so you probably won't be able to use them as they'll see the fixed pitch of the music and assume that there is no problem.

If you try to do things manually and fix the voice you'll change the pitch of the music.
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby Tim Gillett » Tue Feb 04, 2020 2:31 pm

Obviously changing voice pitch will change music pitch. I mentioned trying to remove the music from the voices perhaps with spectral editing or Music Rebalance so that the voices can then be worked on separately. An advantage here is that the music is not complex, although it does seem to warble a little, so perhaps not too hard to remove.

In the damaged section I attempted to correct an obvious pitch error, where a voice says the word "Si" and it's obviously fast/high pitched. But it would help to compare the damaged section with portions of the undamaged track both before and after this 10 second section to get a feel for how these two voices sound naturally, what their natural pitching range is, phrasing etc. Failing a time base reference within the damaged section, the "normal speech" reference seems the next best thing.
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby oberob2020 » Wed Feb 05, 2020 8:00 pm

Thanks so much for the insight and suggestions. I appreciate it. :thumbup:

I don't have the speech track. I don't believe it exists anymore (possibly destroyed). The BGM track however is available although it's been transferred using different equipment and subjected to a 4% speedup which makes it impossible to just align the two tracks and remove the music. I feel having flutter in the music would be way more preferable than having it in speech as, in any case, there are many sections were the music is actually made to flutter intentionally for a comedic effect.

I tested it on the Celemony Capstan demo and it didn't work at all.

I tried to do both suggestions from Tim. So I used the Pitch Bender from an old version of SoundForge (I never upgraded that again as I have since switched to Adobe Audition - yes, I know audition has a pitch bender too but the one in Soundforge offers more fine tuning). I also tried to grab a few problematic areas from other sections of the recording. The result isn't awful. I would definitely say it's an improvement but it's very far from perfect.

As for calling the actors, one of them sadly passed away last year so that's not an option even if the client agrees to it (which they probably won't anyway as they want it done as cheap as possible).

Here is my result so far: http://www.mediafire.com/file/zy2o009tw ... h.wav/file

I just tried to fix the voices ignoring the music. The few times I tried music rebalance in the past, it gave very artificial results. I was thinking maybe lowering a bit the music and remixing with the BGM track may help out but so far I am more concerned about the voices not sounding right.

This is how the voices normally sound: https://www.mediafire.com/file/hqdfzviz ... c.wav/file
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby Tim Gillett » Thu Feb 06, 2020 5:23 am

That does sound like an improvement. As you say not perfect but I doubt anybody would be able to achieve perfection just working "by ear". Well done.
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby n o i s e f l e ur » Fri Feb 07, 2020 5:35 pm

Would something like Steinberg Spectralayers or even Celemony Melodyne (polyphonic version) be helpful here?
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby Tim Gillett » Fri Feb 07, 2020 9:34 pm

I doubt it. Ceremony Capstan also relies on the polyphonic principle in say an orchestral recording with multiple tonal instruments whose tonal deviations can be correlated. With a single voice speaking there is nothing else with which to correlate its pitch changes. In short there isn't enough information for Capstan to do its work. We need a reference. So we are thrown back to judging the voice by ear. That's my understanding.
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby n o i s e f l e ur » Fri Feb 07, 2020 9:52 pm

Right, it's a judgement thing so it seems to me the goal needs to be to get the thing to sound not-f*cked as opposed to a faithful restoration? Spectralayers looks like it might be able to isolate the offending portion from the rest such that one could get quite creative, or at least very focussed in on that material. Then mix the fix back in.

I'm not suggesting it would be easy or an automatic process, just as a tool to un-mix the source.

Perhaps I've missed the point entirely, it's not a field of endeavor I'm too familiar with. Or is it that the part of the process I'm rowing in on isn't actually an issue, but how to fix the already-isolated part?

Apologies if, with catlike reflexes, I've managed to elude the jist of the thread! :)
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby oberob2020 » Fri Feb 07, 2020 11:06 pm

Doing it by ear alone didn't fix much. What I actually did was trying to draw a curve with the Sounforge pitch bender across the whole of the phrases varying the curves until it sounded the best I could achieve. For the last one (the kid's voice) it was pretty easy as it was an almost perfect y=inv(tanx) which immediately fixed it. The man's voice though seems more problematic. The pitch doesn't seem to vary according to a specific model. I did fit in the best curve I could but it still sounds wrong to me. I think either the pitch is varying erratically in that section or there is some other issue I can't grasp. Mechanically the tape has to speed up and down for the flutter to occur. It was recorded on analog tape so I doubt that the variation could be that erratic so as not to follow any rule.

I am not familiar with Spectralayers but I will try it out to see if I can achieve any improvement. Thanks to all for the helpful recommendations. I wasn't expecting so many responses and helpful people. Seems like this is a great community here. :)
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby James Perrett » Fri Feb 07, 2020 11:41 pm

oberob2020 wrote:It was recorded on analog tape so I doubt that the variation could be that erratic so as not to follow any rule.

As I mentioned before, it sounds like the tape reel was snagging on something so it may well be almost random - although, if the obstruction was suddenly removed the speed up would follow the same characteristic on each time the problem occurred.
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Re: Weird Pitch Bending in very old Audio File for Restoration

Postby Tim Gillett » Sat Feb 08, 2020 4:01 am

This is perhaps a bit out of left field but I thought I'd throw it in just in case. Since some of the background music has some deliberate pitch bending for comedic effect, is it possible the pitch bending in the short voice sample was also inserted deliberately for similar comedic effect?
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