Fixing "Thump" Sound

[Okiba]

Hi everyone,

98% of the VHS captures I did sounds great. A bit "hissy", but I assume that's normal to Analog audio. However, some videos were captured from problematic tapes, and not only the video is effects, but also the sound. I'm attaching an example. Note the "Thump" every couple of frames (it's being shot at the pool, so the muffled voices is actually because it's an open space).

Is that something I can fix with Audiocity? AI tried Click removal, but that didn't work.

Also, I'm note sure my workflow is correct. I assume that I shouldn't modify the Lossless file. But instead, extract the Audio from the lossless file. I can do that by loading the file into AudioCity (and using the FFMPEG plugin for AudioCity). But I'm not sure if that separate the audio correctly? ie - keep the original loseless audio quality?

And once I have the audio aside, tweak it to fix it, save it was "wav" (because wav as far as I know is loseless format), and when I encode the loseless file into the final form (x264 with ffmpeg), I should somehow tell ffmpeg to use this audio file instead of the original loseless audio channel? and ffmpeg will compress the quality of the wav while also doing that for the video?

And perhaps last question while we here speaking about audio fixing and VHS. Is there any that is always a good idea to do to improve VHS audio (while I already tweaking the audio)? perhaps remove hissing somehow? improve quality? etc.

Thanks!

[jagabo]

Is that something I can fix with Audiocity? AI tried Click removal, but that didn't work.

High-pass filter, around 200 Hz.

[Okiba]

Hi jagabo, thanks for the reply.
I played around with multiple High pass values and the Octaves, I still hearing that, but less - It more of a "Click" now. That's the best can be done? Also, can apply that to all the file? or manually need to select the problematic peak (I have manyyy of those in some videos). Won't applying it to the all file will hurt details on more noisy sections?

[hello_hello]

jagabo's high pass filter suggestion is a sane one, however if insane is an option, turning the thumps down manually qualifies.

Hunt down a thump (just after the selection point here).


[Attachment 55665 - Click to enlarge]

Select a small area around the thump and zoom in to the selected area.


[Attachment 55666 - Click to enlarge]

Highlight just the thump and reduce the volume (Amplify effect). -10dB seems enough.


[Attachment 55667 - Click to enlarge]

Zoom out and re-commence thump hunting.


[Attachment 55668 - Click to enlarge]

[jagabo]

I played around with multiple High pass values and the Octaves, I still hearing that, but less - It more of a "Click" now. That's the best can be done?

You can try using the notch filter. Find the fundamental frequency (trial and error) then apply a sharp notch filter at that frequency and its harmonics. There may be more than one fundamental.

Also, can apply that to all the file? or manually need to select the problematic peak (I have manyyy of those in some videos). Won't applying it to the all file will hurt details on more noisy sections?

If you apply it to the entire file you might be able to tell that some of the low frequency background noise is gone. If there is music or a low pitched male voice some of the base will be gone. Obviously, locating them and manually treating each one would be tedious.

[johnmeyer]

You have two problems. You have a "motorboating" set of thumps at very regular intervals, as shown by the green arrows, and then you have non-periodic, much louder thumps indicated by the red arrows.

You say that you have hiss which indicates that you might be capturing from the analog linear channel. However, that motorboating is something I have heard quite often on Hi-Fi channels captured on my hi-end Panasonic deck which, unfortunately, has a misaligned Hi-Fi problem.

Exactly what is the nature of this tape? Roughly what year was it created? Are you capturing the linear (analog) channel or the Hi-Fi channel? What tape speed is used (2-hour, 4-hour, 6-hour)? If this is Hi-Fi and is caused by your deck being misaligned, using a different deck can eliminate the problem. As an alternative, if you are capturing Hi-Fi you can instead capture the linear channel. This will degrade the audio somewhat (it will degrade a LOT if it is a 6-hour tape), but the thumps will almost certainly be gone.

As you can see from the second picture, I fixed it by repairing the big thumps using "Spectral Repair" in iZotope RX. I was very sloppy with the settings which is why you see some of the high frequency material eliminated. If I'd spent an extra couple of minutes to set it up correctly, the repair would have been 100% perfect. For the motorboating, I used the Declick tool, which is normally used to remove clicks and pops from records, but has a setting that lets you widen the click removal and another setting that only looks for low-frequency "clicks" (i.e., "thumps"). As you can see, it removed that completely. I have attached a file that lets you hear the results.

[Okiba]

however if insane is an option, turning the thumps down manually qualifies.

Thank you! Learned something new, and I will use it manually on other tapes where the "Thump" is not on interval (but somethings that happens specifically).

If you apply it to the entire file you might be able to tell that some of the low frequency background noise is gone

I'll do some testing. Talk to a mic, use High pass, and compare to the same file without it. Perhaps I won't even be able to notice that...

Exactly what is the nature of this tape? Roughly what year was it created?

If I recall correctly, somewhere between 1985 and 1990. It's around 3 hours long.

Using a different deck can eliminate the problem

That's what I did at the end. I have two VHS decks. A Combo unit (LG RC288) and VHS only (LG GC990NW). That specific video looks quite bad on the Combo Unit. There's some correction happening by the device to the signal, and it didn't work well. It looks much better on the non digitized signal the LG GC990NW (VHS Only) produce. Problem is - the "Thumps" sounds can be hears on the VHS-Deck only (and not on the Combo Deck). What I did - is a bit slow, but I capture both, and copied the good Audio channel from the combo unit over the bad one. Slow - but, works

Thank you all!