Buzzing audio during capture

[crbd98]

Hello All,

The content that I captured from some VHS-C tapes (using VirtualDub) exhibited a buzzing artifact in the audio, as shown in the attached file VideoWithBadAudio.avi. After some investigation, I noticed that all tapes that were recorded in extended mode (EP) and were captured using a VCR exhibited the same artifact.

I tried many combinations using:
- Two different VCRs (both LiteOn LVS-9036G) and a VHS-C Camera (JVC GR-AX710),
- Two different capture cards (Hauppauge 610 and Diamond VC500), and
- Two different PCs (Dell Precision M4800, i7 quad, SSDs, etc).
I concluded that all tapes that were captured using one of the VCRs exhibited the artifact, regardless of the capture card and PC used. The tapes captured with the camera did not (as demonstrated by the attached file VideoWithGoodAudio.avi).

As mentioned above, this only affected the VHS-C tapes recorded in EP mode. Capturing tapes that were recorded in Standard mode (SP) resulted in files without audio artifacts regardless of the playback device.

Interestingly, there was no buzzing when playing the VHS-C tapes in VirtualDub directly from the VCRs.

Just for curiosity, I extracted the audio from VideoWithBadAudio.avi and VideoWithGoodAudio.avi - refer to the attached files BadAudio.wav and GoodAudio.wav. Using Audacity, I applied a Clip Fix Filter (see Figure 4) to the BadAudio.wav, resulting in the attached file BadAudioRepaired.wav, which does not have any buzzing. Figures 1, 2 and 3 below show the waveforms for BadAudio.wav, GoodAudio.wav, and BadAudioRepaired.wav, respectively. Of course, this is a process I would do just as a last resort.

Now, my questions:
1. What are the reasons for such behavior?
2. Is there anything I can do to adjust the audio as the tapes are captured with VirtualDub so I can continue capturing via the VCR? I did not find any audio filter in VDub that I could apply during capture.
3. Would it be better to capture the tapes using the VHS-C camcorder? (I still have the tapes and the very same camcorder used to record the tapes in the first place).
Some people in this forum whose opinions I value highly seemed to disagree in the approach: some stated that I should use the machine which was used to record the tape, some stated that I should never use a VHS-C camcorder, and some stated that I should try both, compare the results, and pick the one that I found best. I followed the latter - comparing the capture from the camera with the one from the VCR. The video capture using the VCR seemed much clearer (of course, I did not check the audio at the time )

Finally, I understand that VHS-C in itself is a very poor format and that using it in EP mode makes things much worse. I am not looking for miracles but just trying to capture as much sensible information from the tapes as possible (making some "rock juice" ).

Your advice is greatly appreciated.

Regards
Crbd98

Figure 1: BadAudio.wav waveform

[Attachment 58112 - Click to enlarge]

Figure 2: GoodAudio.wav waveform

[Attachment 58113 - Click to enlarge]

Figure 3: BadAudioRepaired.wav waveform

[Attachment 58114 - Click to enlarge]

Figure 4: Clip Fix Filter in Audacity

[Attachment 58115 - Click to enlarge]

[dellsam34]

That's what's called audio level clipping, When your source level is higher than the input is capable of, This can be fixed by lowering the audio level in the capture card's audio properties.

[crbd98]

Hello dellsam34,

Thank you for your suggestion.

I tried to reduce the levels for the capture device (Diamond VC500 card) using VDub>Audio>AudioMixer. It was originally set to 54 and I made various captures reducing the levels to 45, 40, 30, 20, 10, and (finally) 5 but all of them still had the clipping problem. I also tried my Hauppauge 610 capture card but did not get any options to set the level of that device.

Is this what you recommended me to do? I wonder if I am doing something wrong.

Below I attach a picture of the Property page where I set the Levels for the device.


[Attachment 58145 - Click to enlarge]

Thank you
crbd98

[crbd98]

Hello All,

Just closing the loop for everybody's benefit.

I contacted the manufacturer of both my capture cards - Diamond VC500 and Hauppauge 610 - and they confirmed that the capture volume cannot be adjusted in either card. Following some suggestions posted in another thread, I purchased a simple audio level controller and connected it between the VCR and the capture card. After some trial and error, I found by how much I had to drop the audio level to prevent clipping altogether. The resulting volume was only dropped by some decibels and did not affect the ability to hear the audio at all.

That was an interesting learning experience

Thank you @dellsam34 for giving the right name to the problem I was having and pointing to me to a possible solution.

Regards
crbd98