How to fix audio flutter, warble?
 

I have an audio sample here, extracted via PowerDirector.
The tape is a VHS-c, SLP/EP, the adapter(s) are CP7u, I used 3 SVCRs.
Two 7800u and a Toshiba W-808, all play the same regarding the audio. The Toshiba plays the SLP video better but that is not my concern.
Several of these tapes have this warble, I believe those are all SLP/EP.
Is there anything I can try to mitigate the warble? Pitch adjustment in AudioDirector failed to make any improvement.

Standard tools for reducing audio wow and/or flutter are Celemony Capstan and the Wow and Flutter tool within Izotope RX11.

This may be a difficult assignment though as there is a fair amount of background noise from a crowd which will make it harder for the tool to lock onto the musical track pitch changes.

Is there any sign of picture disturbance when these tapes are played back?

Thank you for downloading and listening to that mess. When I play it in my 7800s there is some instability or interference at the top, but not in the Toshiba, so I’m attributing that to SLP/EP tracking.
So…I looked at that Izotopy thing, seems very impressive.
I kept scrolling thru and then saw the price. I think I peed a little.

Yes both are not cheap. RX advanced has a free trial period of a week or so.

Fix the problem at the source not by patching expensive solutions even if it takes capturing the audio only with another VCR and stitch it back to the video file, I've read that people had success routing the audio to an audio capture card rather than the video capture card. So it seems that audio chirp is driver related not a mechanical defect. But if it is indeed a mechanical problem it should be looked at by inspecting the pinch roller or replacing it as well as cleaning the tape path and lubing moving parts.

I agree eliminate any mechanical causes first but I assume if the flutter is common to all three playback decks, the decks are unlikely to be the problem. Other common factors are the VHS C adaptor and the cassette.

I tried both my adapters, and checked the batteries.
Actually I ran a section thru Levelator but that did nothing in this situation.
My next move will be to try my JVC camcorder. Another sparkling new in the box find.
I know it’s not necessarily recommended but I bought it because I wanted one, and like me, cheap.
Maybe there’ll be a chance of being better, but it’s a nasty recording. I’ll follow up.

Well, I gave the JVC camcorder a try. If anything it’s worse.
This was a good exercise but it’s over. They cannot be fixed without expensive audio software and even then the outcome would probably be crapola.

I believe this is not a rocket science. If your VHS player has no flutter but has when playing VHS-C with adapter, problem is in adapter or VHS-C cassette. Good adapter is a must for quality VHS-C playback. I tried several (some like Philips branded (forgot a model) simply did not recognized by some Panasonic TOTL decks) and now stay with Panasonic VW-TCA7E for years. Just make some simple tests.

Uh…perhaps you missed my follow up. Rocket science…

Consumer Reports dinged many VHS-C camcorders for having bad audio flutter, especially at EP speed, even when they were brand new. So if the flutter is "baked into" the original recording, then not even the most flutter-free VCR will be able to eliminate it. You'll need to use a digital plugin to try to correct it.

Exactly. And I have experience with bad VHS-C shell mechanics too. But if so you can always transplant tape to standard VHS shell (leave most of original VHS tape on VHS reel for better performance and splice VHS-C tape at the beginning).

The OP needs to confirm the problem in the tape by connecting the VCR to a TV or a HiFi system, Alternatively the camcorder internal speaker before going out and start spending money, If there is no flutter then it's a driver issue of the capture card.

Used multiple capture cards. And the internal speaker of the JVC camcorder clearly put forth the garbage audio.
It’s a lost cause. But it’s great to know so many smart people are willing to help.

Not sure how important the contents are, but there are some direct playback VHS-C decks with the JVC BR-S series coming to mind. If you've already done the best captures you can, I'd be willing to capture those for you for free using a refurbed BR-S machine. What makes them unique is they can reconfigure their decks to directly accept VHS-C without the need of an adapter. They do contain TBCs as well and as a bonus weigh around 50lbs. The decks are extremely complex and I don't particularly recommend picking one up unless it works. Whatever lubricant they originally used likes to harden and it is quite an involved process to remove and relube it. It also does not use a rotary transformer and instead opts for a head preamp stuck not top of the drum with slip rings to transmit the RF to the rest of the machine. It's also the only VCR line that I've seen that can defeat macrovision internally (without an external device), not that it likely matters for VHS-C.

Easier thing to do would be just to put the tape into a regular VHS donor tape and play it as usual off of that without needing an adapter.

Either way, I wouldn't expect hifi to have to have audio flutter, and could just be that the hifi track is not being read or perhaps was not recorded as hifi and it's going back to monolinear which would be more dependent on how smoothly the recording and playback mechanisms is/were operating I would think. I did see some specs on the BR-S units that say that the linear wow/flutter is 0.25%, not sure if that's a commonly posted spec on other models or not, but interesting nonetheless. Does suggest that wow and flutter are really only a thing for linear audio.

It's an interesting problem. Trying to account for factors earlier in the chain, I've considered a couple of possibilities. W/F is easier to notice in music than speech. If we only had the crowd sounds in that clip would we still notice the W/F? Another possibility that the W/F was actually only in a faulty PA music playback at the venue where the video was shot.

Barry, does this W/F occur only on musical passages? Only on Public Address music recordings played at this venue?

Actually, on further thought, the BR-S's won't play SLP/EP (they are SP only), so that's out.

The audio wow is everywhere but the nature of music makes it worse.

https://www.celemony.com/en/capstan runs $199 for a 5 day rental, for important one or two of fprojects I guess. (Their demo is export and duration limited)

Izotope included wow/flutter starting with RX 8 Advanced. Maybe someone is selling an older version, or has a studio nearby you could get time in at a reasonable cost?

Thanks for that.

Unfortunately Celemony Capstan only works on music and then only on certain music recordings. It doesnt work on speech. I believe RX W&F works on the same principle as Capstan.

Capstan allows ongoing free processing of I think 7 seconds of a recording at a time which can be enough to give an indication of its ability on a specific section. I tried it on a sung section of Barry's upload unfortunately without success.

The software cant perform miracles. It relies on time base indicators within the music itself and works best with multiple musical instruments playing at the same time, such as in an orchestra.

Another approach is to use an accidentally recorded steady hum or whistle in the recording, often a tone well above the range of human hearing, as a time base reference. Plangent Process have been the experts in this audio restoration area for many years but the process requires specialised hardware, software and expertise. It's not just a plugin you can purchase.

If that's the case then it's baked in the tape, proceed with alternative solutions if the contents are important.

There is tape slipping at pinch roller. So this is not constant wow what can be corrected by software.
And Celemony capstan never worked for me anyway, it correct well constant tone, from 3150 vinyl test record for example;)).
In this case it could happen because of bad VHS-C shell and or bad adapter.
If it is recorded you have a problem. The first try to replace particular shell with new good shell.

Replacing the shell may be the only option remaining, but I think it’s just the format, the recording at SLP/EP, and age.

Just throwing an idea, I don't know if this could even work and it requires a lot of time and effort both in hardware and software: the control track is recorded by a head placed on the same assembly as the linear audio head. The control track is a known reference waveform recorded by the original VCR, which in your tape should now appear with the same wow and flutter as the audio track. The playback VCR is already using this track to adjust its speed, but may be not using it to its fullest capabilities, which could perhaps be taken advantage of in software to counteract this flutter. I don't know the signal levels and frequency characteristics of the control track, but maybe you could tap into this signal and feed it with appropiate levels to one of the stereo channels of your sound card, and with the other channel record the mono audio output. You would end up with a two channel audio file, where the first track is the control track waveform, and the second track is the audio, both with the same flutter. Then, a software should be developed to analyse this control track against an ideal control track without flutter, extract the flutter characteristics to correct the original control track, and then apply the same correction to the audio to suppress the flutter. I am not aware of any software that exists that can do this, and the other concern I have with this is that the control track is a pulse at 50 Hz (PAL) or 60 Hz (NTSC), which may not be affected by the possibly higher frequency flutter of your recording and thus it would not help in suppressing it.

Yes I was thinking along the same lines, assuming the flutter occurred at the record stage. As you say the recorded control track should have the same flutter as the linear audio track. This sort of thing is the principle on which Jamie Howarth and John Chester have used in their Plangent Process for many years, although I believe much of their work has used potentially the way more detailed time base information contained in the recorded analog bias frequency which can extend up to 100 kHz or more. But I also remember reading that they have been able to use the much lower frequency audible tones in audio recordings in cases where the bias tone cannot be retrieved, which is quite often, for example in consumer analog audio and video cassette recordings with way lower tape speeds than professional analog audio and video recordings.

A rough measurement I made of the flutter in Barry's sample put it at about 8 Hz, so below the 50 or 60 Hz control track frequency. So maybe the control track would carry enough information to be useful in correcting that sort of flutter frequency, whether partly or fully.


But I know this is non standard practice and would likely run into more expense than the average person would wish to pay for reducing their home movie audio's flutter. I suspect Plangent has been used mainly on high profile audio recordings where profits from a popular artist's remastered album would justify the expense.

The attached spectrum below is of an open reel recording made in the early 50's where the tape slowed in the last minutes of the recording. A loud 50 Hz mains hum plus harmonics was also accidentally recorded which I guess could be used to correct speed to some degree. Interestingly here there is both a short term speed error shown as a cyclical wow or flutter similar to Barry's example, but here also a much slower, long term drift upwards, representing the gradual slowing of the tape when originally recorded.

Thanks for your comments.

Ah yes, the old Plangent Process trick…how could I be so dumb…?