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-   -   Fixing VHS-C audio problems - Project Notes for Al (http://www.digitalfaq.com/forum/video-restore/2374-fixing-vhs-audio.html)

kpmedia 08-19-2010 07:40 PM

Fixing VHS-C audio problems - Project Notes for Al
 
NOTE: Although this information is being written for a specific person, for his specific project, it may help others to correct (or at least understand) their own audio issues, when dealing with VHS-C type recordings. It would also apply to 8mm, Hi8, S-VHS-C and possibly DV recordings...
...


What I ran into on some of your tapes is what (at first) appears to be silent recordings. I think you had noticed that, too -- I'd have to double-check some of the emails.

I also notice what looks to be in-camera editing, maybe. Recordings fade to white, then the next clip fades from white to video. Other tapes are just on/off recordings, sometimes with chroma noise visible (the red/blue vertical stripe caused by a lack of a flying erase head in the VHS-C camera used), and other times with a "snow" gap (unrecorded tape).

Tracking was pretty rough on the on/off tapes, with the first 20-60 seconds of each recording lost as the camera struggled to record on a set path (when recording), and then a VCR trying to follow that path (when playing). In almost all cases, it was dump-able footage anyway. The one scene that was too precious to dump was restored, as per a separate email sent over the weekend.

Without reviewing all clips with problems, I believe it was almost entirely the white fading clips that suffered loss of audio. Were two cameras used in the lifetime that these tapes were made? Circa 1990-1998.

Upon further inspection, it appears the audio is not missing or muted, but simply quieted to a point where inherent tape noise (hiss, hum and buzz) overtakes what little is left. In other words, I can hear some audio, with a mixer boosting the gain at unreasonable levels, and the speakers on max, but it's just an echo or a ghost version of what it should have been (or maybe once was, if these tapes are edited generations).

When somebody's talking, for example, all I can hear is BBBBZZZZZZZTTTTTTT with a SSSSSSSSSSSSSSS sound, with the pitch and sound of a voice underneath it. It's impossible to make out any of the words. It's just "human sounds," if you will. I just went ahead and muted it in most places. It's gone.

I believe a defect in the camera's microphone may be to blame. However, it could also have been caused by in-camera editing gone awry. It's really hard to say, given what little I have to go on.

A couple of recordings were louder, with people yelling or talking really loud, and you can sort-of make out what was said, as the audio comes and goes. One segment was a recording from a concert, and you can still hear a lot of the music. It was way too loud to be recorded with a cheap consumer camcorder (distortions galore), but it was loud enough to punch through whatever defect was silencing the audio. It was just loud enough to be about even with the underlying tape noise, so I was able to suppress the tape's hiss and buzz, and bring out more of the actual audio. Then I did some work to un-distort it. That's from one of the Disney World tapes you shot on a vacation.

Even when the camera was properly recording the audio, it suffered from a common issue -- the tape's microphone picked up the camera's own operational sounds. So any kind of zooming of the lens, handling of the camera, the sound of the tape spinning -- it's all recorded as audio noise. It's a hiss with a hum, plus a light buzzing sound. I've been able to kill most of that obnoxious noise, for a majority of the tapes. At very least, it's reduced in all recordings.

Noise reduction is often dependent on locating a proper noise print or creating a noise profile, and some of the recording were pure sound -- hard to isolate a print or profile. It will be difficult to hear in these clips, anyway, as there's a lot of talking and/or music and sounds going on.

All in all, it's much improved. Looks great, sounds good, archived to high bitrate DVDs with some simple-yet-attractive menus pointing to the different clips.

As per initial project specs, the video tapes were chopped into smaller recordings, and arranged by date. As you recall, some tapes were randomly used, on an apparent "space available" type of system, with everything being a bit out of order at times. The DVD series is in chronological order, so you can watch the family age and grow up together across the near-decade you shot home movies with this video format.

...
... will continue this in email again from this point. Just wanted to share the tech and non-identifying notes in public, for others that may benefit.


Thanks. :)


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