Mini DV: left-right audio levels mismatch, maybe 12bit-16bit issue?

[Encode8489]

I was checking some Mini DV tape captures (digital, with Firewire), and on all them the volume levels are not the same for left and right channel (left too low? or right too high?)

All the tapes were recorded by the same camcorder, so I'm not sure if it could be a hardware defect of the microphone, or if something went wrong with the encoding. In particular, I think the tapes were recorded with 12 bit audio, while with mediainfo I see the audio is 16 bit.

Do you have any ideas on how to solve this problem?

I attach a piece of video with the issue.

[Bwaak]

Professionals often split one channel into two with different levels, as on the one hand you want as high level as possible, on another hand you want ro avoid clipping. This allows to mix and match. Usually there is 10dB or 20dB difference.

[Encode8489]

I don't think it's my case, my camcorder is a JVC GR-D24, is it simply marked as stereo audio, and I don't find any settings about that.
Also, the files have just two audio channels, they should be four if they were splitted...

[pchan]

Clean the firewire cable contacts with contact cleaner. Clean the PC side first i.e. spray on the firewire and PC. If the problem is still there, do it on the camera side. If all else fail, edit the audio tracks with Audacity by adjusting the left/right channel balance of the audio track.


[Attachment 74502 - Click to enlarge]

[dellsam34]

Audio level has absolutely nothing to do with firewire port being dirty, If that was the case video and audio will have dropouts not level issue on one channel, Because the data has not being decoded yet into video and audio coming in to computer. This is most likely source related, which means internal microphone or external plug in one.

[jagabo]

That sounds like front/rear stereo, not left right stereo. Either that or the source of the audio was off to the side, not in front of the camera.

[Cornucopia]

Or the manual audio levels were set wrong.


Scott

[jagabo]

It's not just a matter of levels. The frequency distribution and phase are different too.

[Encode8489]

The microphone used is the internal stereo. As far I can tell, it's front stereo, I see on the front of the camcorder a grid labeled "R L STEREO".
On the manual (and on the settings menu) the only setting I found about audio is 12bit/16 bit, I cannot find any level regulation.


[Attachment 74519 - Click to enlarge]

[Bwaak]

Whatever the case, it is too late to adjust the camcorder now. Just adjust the captured audio and move on.

[Encode8489]

Yes, sure, I'm just trying to understand what is the best way to fix it, and as I have a lot of material with the same issue, I'm preferably looking for an automatic way to do it, like with an ffmpeg command.
I'm not sure if it makes sense to balance the audio or, considering that the two microphones are very close, just discard one of the two channels and make it mono.

[jagabo]

Could it be raw mid/side stereo (see #3 here: https://www.sweetwater.com/insync/stereo-mic-techniques/ ) without the re-mix (M+S, M-S) ?

[Cornucopia]

Those samples could be tested with a M/S --> L/R decoder remix.
(sorry, don't have time for that myself)


Scott

[jagabo]

Those samples could be tested with a M/S --> L/R decoder remix.

Yes, I did a simple L=(F+S)/2, R=(F-S)/2 with Audacity. The result sounded ok but was pretty much mono. But that may be the nature of that particular recording.

[Encode8489]

It sounds interesting, but I'm not sure,.. as you said, it looks mono, and also the left channel is always lower than the right.

I also tried to do a new recording, with a moving speaker, playing the same sound at the left of the camcorder, at the center, and at the right, but it doesn't look stereo even with M/S decoding.

[pchan]

This camcorder is quite old so the electronics might have deteriorated.

Back to Audacity again. If you want it to be like this...

[Attachment 74539 - Click to enlarge]

Here are the steps...
1. Drag and drop the AVI file into Audacity.
2. At the top of the track, click dropdown menu(Shift + M) and select Split Audio Track
3. Now that the left and right channels are split into 2, at the bottom of each track, click select and go to Effect and select Normalize...
4. Repeat step 3 for the other track.
5. Repeat step 2 but now, select Make Stereo Track
6. File -> Export to your format that you want

[jagabo]

So the file you uploaded is the original? And the three tone bursts are audio source on the left, audio source in the middle, then audio source on the right? If that's the case I think there's just something wrong with the camera. All three positions have the same phase shift between the two channels. But if they were front/side channels the three tests should have different phase shifts. In fact the left and right tests should have the opposite phase on the side channel.

How about trying one with all four directions: left, front, right, back.

[dellsam34]

Obviously the demultiplexing circuit for stereo audio is faulty, DV camcorders are not that expensive, do yourself a favor and get another working one, you'll save a lot of Audacity use time.

[pchan]

Obviously the demultiplexing circuit for stereo audio is faulty, DV camcorders are not that expensive, do yourself a favor and get another working one, you'll save a lot of Audacity use time.

The only DV camcorders available are from Ebay or some used electronic website. I think TS is using the camcorder as playback. Since the taped source is bad, even a good camcorder can fix it ?

[dellsam34]

No, Depends on when they were recorded, before the camcorder gone bad or after, And possibly only the playback is affected, the camcorder could still record stereo just fine but the playback circuit is bad, The only way to find out is to get another working camcorder, Off course from used market, what else he's gonna get it from? Walmart?

[pchan]

No, Depends on when they were recorded, before the camcorder gone bad or after, And possibly only the playback is affected, the camcorder could still record stereo just fine but the playback circuit is bad, The only way to find out is to get another working camcorder, Off course from used market, what else he's gonna get it from? Walmart?

Since you mention Walmart, this might be an option.
https://www.dvdwalmart.com/services-and-pricing

If Walmart could do it, then a working camcorder might.