Videotape restoration

[dowkeith]

I have DC7. Is there any way with this or another Diamond Cut product to clean up the buzz on the audio track
of some old DVDs, which were professionally recorded? The sound track now has an annoying buzz.

[Craig Maier]

Hi,

I have never done this but have heard of people doing that. Somehow, they extract the audio portion of the program into Diamond Cut (.avi or something like that) and then clean the audio and then somehow glue the clean audio track back onto the video. I hope someone here who has done it will respond with specifics.

Craig

[ric29]

I assume you are talking about VHS or similar system (analog).
The first step is to run spectrum analyzer and see additional signals which come from video part of the recording. Because of some technical reasons such signals are added to the audio track.
I don't know what TV system has been used in your case but in PAL system (I am from Europe) it is 15625 Hz and few other high frequencies and few low (50 Hz plus its harmonics) which are generated by electronic part of the video recorder.
So at the beginning you have to use a notch filter to cut them from the signal.
The rest depands on the audio signal (speech or music, level and kind of noises, etc.) and your expectations.

BTW-the word "buzz" has got few meannings. English is not my native language so I can't discuss about it but some annoying noises, often called as a buzz, come from mentioned above video signal so it makes sense to focus an attention on such analyze first.

[Craig Maier]

Hi,

Often, "Buzz" is differentiated from "Hum" based on the harmonic content of the noise signal. In other words, "Buzz" is harmonically rich "Hum" (not a good thing). A notch filter (or a few of them) are often used to reduce "Hum" but "Buzz" is often attenuated with the Harmonic Reject Filter. Hum and/or Buzz can also be attenuated using the Diamond Cut Forensics version Spectral Filter.

Craig

[Dan McDonald]

and occasionally the buzz can be eliminated by use of the impulse filters, but that can be tricky to get exactly right.

[dowkeith]

Hi Craig,

You helped me a lot once before on another issue. This is a common thing (for me at least) on older tapes.The soundtrack seems to go before the video. It's the same kind of sound you can get on a radio when some other thing produces electrical interference. I thank everyone for their suggestions. I think I could eliminate the hum, but this is more complicated than that. Even if I cleaned up the soundtrack how can I sync the cleaned up version with the video? Since Roxio and others make products for editing video, and Diamond Cut is great or cleaning up audio, I was hoping one of the two made a program for dealing with this common problem on old tapes.

dowkeith

[dowkeith]

I think I could clean it up using DC7 orDC8. I have worked cleaning up audio tapes, but videotapes present an added problem of synchronizing the cleaned-up audio with the video. I was hoping someone knew of a program that addressed this issue, which is common among older videotapes.

[Craig Maier]

Hi,

My understanding of the issue is that most video editing programs provide a method to separate the sound track out from the video track. Then, you should be able to import the audio into Diamond Cut and use whatever tools are needed to fix the sound. Then, one would (in theory) take the cleaned track and export it back to the Video editor and replace the original audio with the cleaned audio.

Hopefully, someone here who has done it can comment.

Craig

[Joeybear]

I do this all the time; especially with older video tapes that aren't in the best of shape. Most reputable video editors will automatically separate the audio and video into separate tracks. From there, you can mute the video track in the editor, then "render" (export) the audio in whatever audio format you want.

Once you're done doing your cleanup in DC, you're almost ready to drop the cleaned up audio back into the video editor. The reason I say "almost" is for one simple reason... In DC, clean the audio, but DO NOT change it timewise. By doing this, you'll be able to simply drag and drop the clean audio into the video editor without synch issues. During the drag and drop, the editor will automatically create a new (3rd) track for the clean audio. At this point, mute the original (buzzing) audio track, then unmute the video track. If everything is OK, render the entire project in whatever video format you need.

As for your specific comments regarding synch problems, many low cost capture devices and video editors are notorious for synch problems. This is certainly an area where spending a little more money up front now will save you countless hours of frustration down the road. Your current synch issues are more than likely the result of skimping on the capture card and/or the video editor. If it were me, I'd start with getting a better capture card. I'll send you a message with specific recommendations.

One final suggestion... if you're creating a new DVD, render the video as MPEG2 and the audio as Dolby AC3. This will involve 2 renders from the video editor (one for audio and one for video), but the difference in sound quality is worth it. Most good DVD authoring programs give you this option.

[Dan McDonald]

Yes, all the video editing software lets you sync up the video.

[ric29]

how can I sync the cleaned up version with the video?

VirtualDub allows to take control over such things

[Craig Maier]

Video tape 'buzz' is often the result of "Vertical Sync Bleed-through" onto the soundtrack. In the US, its repetition rate is 30 Hz and in Europe it is 25 Hz and in both cases, it is harmonically rich and thus needs the Harmonic reject filter to help out.

Craig