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  #1  
06-27-2012, 12:14 AM
Belmont Belmont is offline
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I've picked up a new VCR to replace the Sony when the linear audio on that machine began to muss up (backtension error caused warbly audio), a JVC HR-J692U (consumer) VHS Hifi VCR. Not the best, and it has it's problems, but it produces a really good picture and tracks well for the most part (the Video Stabilization comes in handy at times, but it's a pain in the wazoo at other times, but that's another subject for another thread).

But there's just one tiny little problem with linear audio. While EP linear audio is less then stellar at best, and full of hiss and warble, I've noticed that consumer JVC VHS decks have a strange problem with it. When I first insert an EP mode tape with linear audio and hit Play, the audio for a few seconds sounds amazingly clear, and then suddenly dulls out. I've only noticed this on JVC VHS decks from the late '90s, and not on any Sony's or Panasonic's. Do JVC VHS decks apply some type of noise reduction/hiss filter, like Dolby B (I know some linear stereo decks in the '80s did that to cover up the abysmal audio of linear stereo)? Or does it have to do with the quality of the audio heads and the record deck in general? All my linear audio tapes were made on JVC's, and I've noticed this phenomenon for awhile. I've half a mind to just pick up a non-JVC non-Hifi VCR just to playback linear audio tapes (anyone else do this for their workflows?) for $5 at the local charity shop

Anyone else have any words of advice?

Here are some examples. They're not the best, and it's somewhat subtle, but I think youse guys will hear it well.

Also, I don't know why the Tape_0024 clip came out black and white. It's like that on the tape, and it's been that way since it was recorded. Must've been some weird copy protection error or a problem with the input signal. And holy crap, the white balance on Tape_0022 is insane!


Attached Files
File Type: mp4 Tape_0024.mp4 (5.32 MB, 31 downloads)
File Type: mp4 Tape_0022.mp4 (4.60 MB, 16 downloads)

Last edited by Belmont; 06-27-2012 at 12:25 AM.
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  #2  
06-27-2012, 02:37 AM
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lordsmurf lordsmurf is offline
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The color issue is probably a wiring issue at time of recording. Video game consoles are also not known for putting out fully compliant NTSC or PAL signals.

There's also obvious timing issues, seen as wiggling in the image. Inside-the-VCR line TBC would help.

I don't hear much difference between the two clips. Both have some kind of audio feedback going on, and that could have been induced anywhere, be it at original source recording time, or within the various hardware now used for transfer. JVC's handling of linear audio has never been superb, but linear audio is itself rather dull and has a tendency to pick up noise. That's one reason HiFi is better.

Attached are the two clips, as audio only, processed to isolate, and the again to amplify the noise.
0024 has the noise repeated, and has a faint pulsing "hammering" noise in the background, in addition to hiss and buzz.

The audio isn't excessively or unreasonably dull to me, listening on high-grade near-reference speakers. The dynamic range is passable, and it sounds like mono audio. It's really not muffled.

The noise is moderately easy to remove, with the right tools and skills. Attached is the noise reduction/removal (NR), as processed in two phases. The first one removed the bulk of the noise, while the second one first refined the NR, then proceeded to re-balance (EQ) the remaining audio to one that sounded more full-bodied and enjoyable.

So even if the VCR or other hardware is a nuisance, and adding some noise to the noise already inherent to the original VHS tape, all of it can be processed out later.

Digital audio has been workable since the early 1990s, unlike video which was really not easily workable until the early 2000s. So audio processing tools are about a decade ahead of video processing tools. Much of what you see on the "CSI" TV shows is fake (for the moment) in regards to video and photo processing, but a reality in regards to audio processing.

And yes, I've been working with digital audio for a long time, since at least 1994, so you learn a few things in 18+ years.

Stuff like this takes a lot of time to help with. You should consider the upgrade to Premium Member.


Attached Files
File Type: wav Tape_0022.wav (4.08 MB, 9 downloads)
File Type: wav Tape_0024.wav (4.59 MB, 2 downloads)
File Type: wav 0022 Noiseprint.wav (1.73 MB, 1 downloads)
File Type: wav 0024 Noiseprint.wav (21.1 KB, 1 downloads)
File Type: wav 0022 Noise Amplified.wav (1.86 MB, 0 downloads)
File Type: wav 0024 Noise Amplified.wav (1.03 MB, 0 downloads)
File Type: wav 0022 NR phase1.wav (4.08 MB, 1 downloads)
File Type: wav 0024 NR phase1.wav (4.59 MB, 1 downloads)
File Type: wav 0022 NR phase2 final.wav (4.08 MB, 2 downloads)
File Type: wav 0024 NR phase2 final.wav (4.59 MB, 3 downloads)

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  #3  
06-27-2012, 02:28 PM
Belmont Belmont is offline
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Quote:
Originally Posted by lordsmurf View Post
The color issue is probably a wiring issue at time of recording. Video game consoles are also not known for putting out fully compliant NTSC or PAL signals.

There's also obvious timing issues, seen as wiggling in the image. Inside-the-VCR line TBC would help.
That would make sense, considering that the wires for the two game consoles were pretty old. I'd have to dig out my SNES and record a bit of gameplay onto a spare blank to see if it was just a problem with the VCR I used when I made those recordings, or just a signal problem with the consoles themselves. I do recall that I tried using the RF adapter to avoid the problem, but it also happened with the RF adapter as well. When I was recording, the image on the TV screen was in full color, but when the tape was played back, it was black & white like you see in the video. Sometimes, there would be color on certain parts of the recording. It's a very strange error.

Quote:
Originally Posted by lordsmurf View Post

I don't hear much difference between the two clips. Both have some kind of audio feedback going on, and that could have been induced anywhere, be it at original source recording time, or within the various hardware now used for transfer. JVC's handling of linear audio has never been superb, but linear audio is itself rather dull and has a tendency to pick up noise. That's one reason HiFi is better.
I do have my VCR stacked on top of a DVR and next to my computer, and I'm using regular RCA cables, so that's more than likely where the noise is coming in. Any good methods of shielding the VCR? Is this interference what's making the audio become more muted after I hit play?
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  #4  
07-01-2012, 01:41 AM
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lordsmurf lordsmurf is offline
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Quote:
Any good methods of shielding the VCR?
Distance from other devices is the most common one.

1" thick wood makes for a good firewall. That's why our custom racks are built of wood, not prefab metal.
The offset is heat, so be sure to lift the decks so air can pass underneath. Rubber door stops work well for this.

Wrapping it in tin foil won't help. For some reason, people always want to wrap things in tin foil.

Quote:
Is this interference what's making the audio become more muted after I hit play?
I doubt it. Interference is noise: hissing, buzzing, humming, etc.

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  #5  
08-05-2012, 10:02 PM
Belmont Belmont is offline
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Quote:
Originally Posted by lordsmurf View Post
Wrapping it in tin foil won't help. For some reason, people always want to wrap things in tin foil.
Didn't Thomas Edison create the first sound recordings by wrapping some tinfoil around a pre-grooved drum?

Anyway, the reason for the bump is that I've ran a sample of the audio from each machine through an audio analyzer, and here are the results (screenshots included):
  • *The JVC seemingly cuts off all frequencies about ~4.5K Hz, while the Sony keeps all the frequencies in, noise and all. it doesn't seem to be a NR thing, because the audio is still hissier than the Sony's. 'Tis interesting.
  • *The audio map of the JVC's output is much smoother and simpler, while the Sony has all sorts of spikes. This may explain why the Sony has a fuller sound while JVC's is "muffled" by comparison. It could be that the JVC is putting out a totally unfiltered sample, and the Sony is "pre-enhancing" the output, giving the illusion of better audio fidelity. I know that many late '90s consumer VHS machines, and even some pro decks like the beloved AG-1980P, would automatically sharpen the video and create haloing/ringing artifacts.
  • *The Sony VCR was beginning to have problems with tape tension, and the extra "fidelity" could have been caused by the tape being pressed against the audio head too hard, which would wear out the tape and thusly make the JVC sound poorer, although I doubt the extra wear was that extreme.
This is totally something I'd like to investigate, because it would definitely matter to some, especially those with a lot of concerts taped with linear audio, or those who just want the best sound quality possible. It's also more than likely that it's common knowledge by now.


Attached Images
File Type: png JVCAudio.png (87.1 KB, 4 downloads)
File Type: png SonyAudio.png (91.7 KB, 4 downloads)
File Type: jpg Screen shot 2012-08-05 at 10.59.00 PM.jpg (80.2 KB, 4 downloads)
File Type: jpg Screen shot 2012-08-05 at 10.58.50 PM.jpg (87.2 KB, 2 downloads)
Attached Files
File Type: mp3 JVC.mp3 (3.94 MB, 3 downloads)
File Type: mp3 Sony.mp3 (3.79 MB, 2 downloads)
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  #6  
08-06-2012, 02:45 PM
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kpmedia kpmedia is offline
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Quote:
This is totally something I'd like to investigate, because it would definitely matter to some, especially those with a lot of concerts taped with linear audio, or those who just want the best sound quality possible.
Please do.

Quote:
It's also more than likely that it's common knowledge by now.
Nope. Otherwise I'd probably know it.

Quote:
I know that many late '90s consumer VHS machines, and even some pro decks like the beloved AG-1980P, would automatically sharpen the video and create haloing/ringing artifacts.
Correct.

Quote:
and the Sony is "pre-enhancing" the output, giving the illusion of better audio fidelity.
Very likely.

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