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Author Topic: Is there a way to remove only sounds that -aren't- in both stereo channels?  (Read 2518 times)

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Offline Nugneant

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Hi all.

Recently I acquired a recording on traded CD-Rs. Unfortunately, somewhere along the line someone was using a burner not quite up to standards, and this introduced a smorgasboard of "digital surface noise" - pops, clicks, et cetera.

These pops and clicks are generally too "scuffy" to be caught by a pop/click filter - if I turn the sensitivity low enough to actually detect the pops and clicks, it also detects lots of sound that isn't a pop nor even a click.  :P

However, the show itself is, for all intents and purposes, a monoraul recording. And the pops and clicks tend to be in one channel at a time.

I know many sound editors offer a "remove vocals" feature, which removes everything that's in mono (or both channels at once). However, is there any way to do the exact opposite of this - that is, remove anything that's not in both channels, and leave the rest? ("Remove music", I guess  ;D)

I tried "removing vocals", then inverting the clicks and garbage that were left, then mixing that into the show - while it sounds better, it's still hardly ideal, and I get the feeling I'm not doing it right.

I have GoldWave and Audacity, and have access to WaveLab and Sound Forge. That's also pretty much my order of expertise - Goldwave > Audacity > WaveLab > Sound Forge.

So, if anyone would like to offer some help, my thanks would be a-plenty :)
« Last Edit: June 10, 2007, 01:20:39 AM by Nugneant »

Offline faninor

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You could open it in an audio editor and then copy/paste the left channel to replace the right channel when there's a pop in the right channel, and vice versa. I don't know of how to remove only sounds that aren't in both channels though. Plus this way, the majority of the recording is untouched, which should be more desirable.

Offline eric.B

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sounds like an easier job would be too look for clean recordings...   what is/are the show/shows?   any information on the source?   If so, try finding something closer to the original or a copy in .flac or .shn...
We have a system that increasingly taxes work and subsidizes nonwork.  ~Milton Friedman

Offline Nugneant

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You could open it in an audio editor and then copy/paste the left channel to replace the right channel when there's a pop in the right channel, and vice versa. I don't know of how to remove only sounds that aren't in both channels though. Plus this way, the majority of the recording is untouched, which should be more desirable.
Trust me, the thought has come to mind, but there are so many clicks and scuffs that doing them all would be a pain in the ass. There're also some scuffs that are in both channels - but very imbalanced (i.e., 75% left, 25% right). So this wouldn't really fix those.

Quote from: eric. B
sounds like an easier job would be too look for clean recordings...   what is/are the show/shows?   any information on the source?   If so, try finding something closer to the original or a copy in .flac or .shn...

The shows in question are Frank Zappa's December 1981 California run - 12/10 Berkeley E/L, 12/11 Santa Monica E/L, and 12/12 San Diego E/L. The San Diego shows have the most clicks of the lot, and are the ones I'm primarily concerned with at the moment.

With most other artists, I can imagine it being painless to put up an ISO request and have goodies rain down like heaven's mana. However, with Zappa, there's a bit of a brick wall - the trouble is that there was a prevailant trader - one of the first to transfer the tapes he had collected to CD and post on file sharing services - who absolutely ruins his stuff, all sorts of nasty EQ, reverb, NR... the dude's either deaf or mentally ill, possibly both. Stuff from him sounds really tinny, with clipping and so much NR that it sounds like a 96K/sec mp3. Anyway, thanks to his efforts in the late 90s and early 2000s, 90% of the circulating recordings come from the stuff he posted to USENET and sold (yes, he sold for a profit as well - real wonderful person  ::) ).

I wish I was exaggerating.

So, the options are either to talk to the hardcores (who are already incredibly busy with other shows), or fix it on my own... or do ten trades for a single show to get one copy that hasn't been damaged by Mr. NR. Fixing it on my own would probably be the quickest option. ;)

dorrcoq

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 the trouble is that there was a prevailant trader - one of the first to transfer the tapes he had collected to CD and post on file sharing services - who absolutely ruins his stuff, all sorts of nasty EQ, reverb, NR... the dude's either deaf or mentally ill, possibly both.

ah, yes...the amazing "NINJA" ::)

Offline Nugneant

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 the trouble is that there was a prevailant trader - one of the first to transfer the tapes he had collected to CD and post on file sharing services - who absolutely ruins his stuff, all sorts of nasty EQ, reverb, NR... the dude's either deaf or mentally ill, possibly both.

ah, yes...the amazing "NINJA" ::)
The one, and thankfully the only...

I hear he's started in on the Santana recordings now... is there no mercy?!


Offline nardo

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The shows in question are Frank Zappa's December 1981 California run - 12/10 Berkeley E/L, 12/11 Santa Monica E/L, and 12/12 San Diego E/L.
12/11 E is still being seeded at Zappateers, only 1 seeder at the moment:
http://zappateers.com/bb/viewtopic.php?t=3685

NINJA is not affiliated with this.

Offline gratefulphish

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Wow, memory blast, I was at the Santa Monica and San Diego shows.  While this guy may be less than a stellar individual, taping Zappa was gutsy.  John Smothers, Frank's bodyguard, would just jump off the stage, plow through the crowd, and grab anyone with a camera, much less a recorder that he could see.  Would not want to have dealt with John under those circumstances.  6'3", 280 lb black belt, who used to like to walk around with a lit cigarette behind his ear (shaved head).
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Offline DSatz

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The simple answer to the original question is "yes." What you describe, in effect, is a crossblending of the two channels. But the more you remove the sounds that aren't in both stereo channels, the more you will make those two channels identical to each other--in other words, the more nearly mono the recording will become.

If you're old enough to remember mono LPs--when they were played on turntables with stereo cartridges, the cartridge would pick up a certain extra amount of noise and rumble due to more or less accidental vertical modulation that was never intended to be part of the signal. By summing the two channels, the vertical modulation (and the corresponding amount of noise and rumble) would be cancelled out, improving the sound quality noticeably. But those were mono recordings.

You may want to try a partial blending of the channels to see whether there is a useful amount of noise reduction that won't cost you the entire stereo effect of your recording. Most two-channel audio editing software will let you set up whatever percentage or decibel-based crossblend you want--that way you can see whether your hypothesis holds up.

If you know anyone who has an Apt Holman preamp or a Crown IC-150 preamp (1970s hifi gear)--they both had continuously variable blend controls instead of just a stereo/mono switch; that's a very useful type of control.

--best regards
music > microphones > a recorder of some sort

 

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