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View Full Version : An urgent message about digital noise reduction


tungarbulb
2005-06-29, 09:01 PM
I’m glad I found Trader’s Den. I wish I’d found it 20 years ago. (I know that would have been impossible, but what the heck :)). Just the same, I need to say something for the benefit of novice sound processors and ultimately the whole trading community.

So far I have downloaded two shows from here via torrent which contain very noticeable digital artifacts as a result of overzealous de-noising. These artifacts - which sound a lot like hearing dozens of wind chimes in the distant background (any sound pros and savvy tapers will know what I’m talking about) are WAY more annoying to listen to than the original analog tape hiss.

When I was getting started with digital sound processing, I too wanted to scrub my analog originals until they sounded like born-digital recordings. I found out the hard way that you can’t do that. You end up killing the high end (something which digital de-noising was supposed to do away with) and introducing the digital janglies which I’ve described above. Listen to some very good commercial CD reissues of analog-source recordings, and you’ll find that some tracks, even ones from major bands like the Stones, have just a touch of residual hiss in the background. The engineers who make their living restoring old tapes know that trading a smidgin of analog hiss for digital distortion, diminished frequency response and other artifacts is not the thing to do. Their equipment is probably a lot more sophisticated than anything we have too. If they can’t make an old master tape sound perfectly noise-free, neither can we.

De-noising is a balancing act. The object is to find the point at which de-noising starts doing more harm than good. Think of it like planing a door to fit a particular doorway. If you very carefully shave off a little wood at a time, you’ll eventually make the door fit properly. Shave off too much wood, and the door will be too small to close properly. Plane the door too fast, and you might gouge the wood. Your digital de-noiser should be set JUST at the point where noise is reduced to a tolerable level and no artifacts have surfaced. A good sound card, amp and headphones will help you a lot. (Most “computer speakers” and built-in sound cards are not suitable for serious audio work, but you already know that.).

Keep the good stuff coming, guys. And I implore you once more, please don’t try to make an old analog recording “sound like a CD”.

gsmyth79
2005-06-29, 10:44 PM
I think it's the policy of TTD to seed unmodified sources. If they are modified the seeder probably notes it...

Which seeds are you talking about specifically? Does anyone else notice these issues in the thread?

Oh, and welcome to the Traders' Den!

Lou
2005-06-29, 11:21 PM
I completely agree with the above post, I'd call the sound "glassy" but it's just an awful sound. When I transfer tapes I NEVER, EVER digitally noise reduce them. I'll only very rarely do traditional noise reduction on the tape deck if I'm going to noise reduce at all. It's gotta be a really harsh noise for me to noise reduce on the deck.

Five
2005-06-30, 12:05 AM
Leave denoising to engineers only, please. If ppl want to up noise-reduced shows we will still accept them with proper documentation in the lineage. Some of the noise-reduced shows I've downloaded have been like a trip thru the FLAC cancer ward. So please avoid nr or if you insist be very very very careful with it.

Great first post, tungarbulb. :clap:

AAR.oner
2005-06-30, 08:58 AM
:clap: good post tungarbulb...this is something we can't stress enough...

tungarbulb
2005-06-30, 03:18 PM
...When I transfer tapes I NEVER, EVER digitally noise reduce them. I'll only very rarely do traditional noise reduction on the tape deck if I'm going to noise reduce at all. It's gotta be a really harsh noise for me to noise reduce on the deck.

I'm a DJ and sometime sound engineer, and I'm pretty much a minimalist. I agree with you that processing should only be done if necessary and only if it makes a noticeable improvement. I'll usually run the de-noiser if the noise on the tape I'm working with is really objectionable. One of my first de-noising projects was a telephone interview which was made on cheap equipment and which also had phone system noise all through it. It definitely took a lot of trial and error (on a 233 Mhz AMD K6!) before I found out how to get rid of the noise without creating new problems, but what a relief to hear the voices minus the garbage!

tungarbulb
2005-06-30, 03:24 PM
...Some of the noise-reduced shows I've downloaded have been like a trip thru the FLAC cancer ward.

Very good analogy. There's nothing like spending hours downloading a promising set only to find that it's been digitally mutilated.

First-time de-noisers should definitely spend a good amount of time practicing up on unimportant recordings or expendable duplicate copies of important ones, until they get good enough to use NR without wreaking sonic havoc.

BTW, thank you all for your kudos!

guygee
2005-07-19, 04:59 AM
(...)
De-noising is a balancing act. The object is to find the point at which de-noising starts doing more harm than good. Think of it like planing a door to fit a particular doorway. If you very carefully shave off a little wood at a time, you’ll eventually make the door fit properly. Shave off too much wood, and the door will be too small to close properly. Plane the door too fast, and you might gouge the wood. Your digital de-noiser should be set JUST at the point where noise is reduced to a tolerable level and no artifacts have surfaced. A good sound card, amp and headphones will help you a lot. (Most “computer speakers” and built-in sound cards are not suitable for serious audio work, but you already know that.).

Keep the good stuff coming, guys. And I implore you once more, please don’t try to make an old analog recording “sound like a CD”.

Very well said, tungarbulb. It should be noted that booters can be just as bad as us "amateurs": I have a "silver" of a Byrds show that was denoised so heavily it sounds like they are playing underwater! Just completely unlistenable.

I once had somebody send me a tape of a show (Wavy Gravy's 50th Birthday) with a request for me to digitize it. The tape was very high-gen, the hiss made it almost unbearable to listen to, so the first step is to try and locate a better source. Unfortunately in this case it turned out that the show was barely circulated, and the best I could do was to trade for two other tapes, which turned out to be just as bad or worse. I had a decent set-up (Naks, good A/Ds, choice of Samplitude, Cool Edit or Sourceforge), but since Side A was a loud Jorma set followed by an acoustic Garcia and Kahn set, it was a real balancing act. My patron was very happy with the results, but I was upset with with slight "wavery" degradation in Jerry's delicate fingerpicking caused by the denoising. I've never circulated this show because of this, as I am torn as whether to release it in all of it's hissy glory, or to release the denoised version (which I agonized over for about 100 hours), or to wait for (or write myself) some kind of new type of denoising software that does a better job of preserving the underlying music.

chazuke
2005-07-19, 05:56 PM
Regardless of what's been said against noise reduction, can you recommend a free NR software and state an URL? I have some recordings here with severe digital damage which cannot be listened unless remastered. It's more for home use and not necessarily for upload.

My opinion, btw: Some stuff must be de-noised, some can, some should not and some must not. So it depends.

guygee
2005-07-23, 10:45 PM
Chazuke - I really do not know of any decent free tools out there, but you might try the "Goldwave" wave editor. It is shareware, but you can downloaded a limited demo (3000 commands total, 150 commands/session). The new version looks like it has various filtering tools:

http://www.goldwave.com/release.php

Remember that broadband noise is much harder to remove (without damaging the music) than other types of noise. For example, "digipops" are usually of short duration and can often be penciled out without leaving an artifact. Same for a single scratch in an otherwise pristine vinyl rip. Analog single-channel droputs often leave a very noticeable noise, even when the dropout duration is between 10-100 ms., but if you carefully cut to mono (try to match levels and slopes at the cut) the human ear "integrates" right though the brief mono and does not detect it.

Severe line noise can be removed by carefully constructing narrow filters at 60 Hz. and its harmonics (120 Hz, 240 Hz...possibly higher). It helps to have a frequency domain sample of the noise without any music to determine the filter parameters, and inevitably you are removing some musical content, so be cautious.

Broadband noise is the real challenge. Tape hiss, wind in the mics, vinyl crackle and rumble, and the guy with whooping cough sitting next to the taper are all examples. Hiss removal tools usually use dynamic filters that set a amplitude trigger based on a noise floor, and use attack and decay settings to try and filter from the top frequencies down, using less filtering when the music is "on" and more in the quiet spots. If way overused, you will hear this strange background, like crazy windchimes, in this case back way off on your settings.
In my experience, acoustic music is the most difficult to remove hiss from, you get an oscillation in the decay of the guitar notes ("waveriness"?) that is not unlike a bad MP3.

In any event, use your ears to compare "before and after", and see if you can find a good spectrograph tool to compare before and after to make sure you are not taking too much off of the high end and/or leaving any other "blocky" artifacts.

(EAC has a spectrograph tool, but watch out for its artifacts (false content from aliasing) in the high end, also there is Sound Software Spectrograph 1.0, not particularly versatile but at least it is free. Still available at:
http://www.sonicspot.com/soundsoftwarespectrograph/soundsoftwarespectrograph.html
)

rerem
2005-07-28, 03:18 PM
The SF2 Soundforge Noise Reduction plug-in (direct x) is much better than others. I personally have a low tolerance for analog hiss. There are DL's I did-and deleted because they were beyond the range of what I can stand,beyond what I can fix. I built a set of very revealing speakers-meaning I hear the good stuff-and the flaws,so I want to enjoy the good stuff without a lot of crud.

Someone mentioned NR on the TAPE DECK???? Okay,a recording CAN be RECORDED in DOLBY B or C or no Dolby. To playback-you playback in the format in which it was ENCODED. You can not just push the Dolby C button on a deck and improve a recording that never had Dolby. Also-Dolby is more of a NOISE PREVENTION. it can not take away noise on the source,it does reduce the accumulation of hiss inherent in making another generation. A lot of analog tapers don't get what dolby is.

The IDEAL is to have an end result as close to how the original event sounded as possible. When the source material involves a multi-gen 30yr old analog originally done on second rate gear,it is pretty easy to improve it using GOOD NR techniques and probably some EQ. I really have no appreciation for the Audio-Vegan mindset that insists every flaw,mistake and shortcoming of the recording process has to be preserved-and yet some folks do butcher the job. The "damaged" recordings referred to above....who has the pre-processed version? Are you SURE it got NR effects and what you heard is not the effects of a badly recorded original,a bad transfer to digital? or just age?
Some recordings I have DO have some NR artifacts or other processing flaws-but were salvage jobs of a recording that was unuseable wreckage otherwise-would have joined a little stack of discs I burned before I realized how awful the sound was.

guygee
2005-08-04, 09:37 PM
The SF2 Soundforge Noise Reduction plug-in (direct x) is much better than others. I personally have a low tolerance for analog hiss. There are DL's I did-and deleted because they were beyond the range of what I can stand,beyond what I can fix. I built a set of very revealing speakers-meaning I hear the good stuff-and the flaws,so I want to enjoy the good stuff without a lot of crud.

I agree, I also have a low tolerence for tape hiss, and although I didn't build my own speakers, the Pro Studio speakers in my system bring out the details over the spectrum pretty well. As the owner of many "medium-gen" cassettes, I would agree that some NR with the proper tools should not be objectionable, especially if better source material is not available. Also (personally) I want to hear the singing well enough to understand the lyrics, I want to hear the bass guitar, I want to hear the top hats, and if the mix is bad, some judicious dynamic EQ'ing can bring these aspects of the music more out to the front. I am also interested in harmonic enhancers, these tools can really bring the music back from the dead, especially if the original recording is overly band-limited

I really have no appreciation for the Audio-Vegan mindset that insists every flaw,mistake and shortcoming of the recording process has to be preserved-and yet some folks do butcher the job. The "damaged" recordings referred to above....who has the pre-processed version? Are you SURE it got NR effects and what you heard is not the effects of a badly recorded original,a bad transfer to digital? or just age?
Some recordings I have DO have some NR artifacts or other processing flaws-but were salvage jobs of a recording that was unuseable wreckage otherwise-would have joined a little stack of discs I burned before I realized how awful the sound was.

You make some good points: if the tape is really high-gen, old or partially demagnetized, the music is badly damaged to begin with. But I think part of the question is, what do we want to preserve for historical purposes? So I can also appreciate the view of the "Audio-Vegan mindset" ;) . The technology of audio restoration will advance. 2nd generation wavelet filtering, dynamic neural network filtering based on particular artists voice prints and "instrument prints" (and high on my list, the "YeeHaw Cowboy Yell Remover Tool")...who knows what the future will bring? In that case, we want to have a copy of the original analog recording with the highest bit resolution and sampling rate preserved, in its purest "granola" form, without any previous signal processing applied. So for our present listening pleasure, remaster (if you prefer), and do it well (including careful documentation), but also archive those 192k/24b A/D files in their raw form for future generations.

ssamadhi97
2005-08-06, 07:56 PM
The big problem with digital NR is simply amateurs who warezed SoundForge or Audition and believe that by doing so they suddenly became audio engineers and can magically remove all the noise from recordings without damaging them badly. Not so. In inexperienced hands digital NR can do a lot (and by that I mean A LOT) of damage to a recording, to the degree where it becomes intolerable to the experienced listener - even though the person who performs the NR might not even notice it due to a lack of experience with NR.

I guess that's what most of us are afraid of.

guygee
2005-08-06, 09:14 PM
I am not sure what the difference is between "amateurs who warezed" and amateurs who buy, but if the term amateur simply means inexperienced, then what better way to train your ears than to buy or otherwise obtain one of these software packages, and try for yourself the different settings and listen to the results. I think it is great if as many people as possible have access to these tools, they will make mistakes, but over time their ears will become trained to hear the artifacts they produce, and we all will benefit. I know that is how it happened with me, going all the way back (don't laugh) to the day I downloaded "wavclean", cranked up the settings, and heard all the weird sounds pouring forth. From the experience of trying different NR and other sound editing tools, now I can easily hear the artifacts in other recordings, including on many of the overly-revered "Silver CDs" that get passed around.

I can also hear them in some of my own struggles to remaster high-gen analog sources, but when I compare to the raw source, it was just a matter of, shall we say, "Polishing the coprolite".

Now when it comes to inexperienced people actually seeding their nifty new "remasters", 1) If the original version is already circulating, who cares? Take a chance on downloading or not. Reputations are built on the quality of the seeds, and bad versions will end up in that proverbial dustbin, 2) If the seeder A/D'ed from an analog source, or from a rare/uncirculating digital source, and applied NR processing, then I think it would be fair if the seeder would offer, upon request, to distribute the raw source in the original form (hopefully 24 bit/high sampling rate) to any person claiming the experience to do a better job, or to anyone offering to archive the files on a publicly accessible site.

rerem
2005-08-13, 02:58 AM
Actually-a big peeve of mine is torrents put out with major clipping. Some of these were recent vintage,from DAT so analog hiss is no factor,but somewhere along the line the waves got major clipping. A few clips are fixable-but if the whole thing is maxed-there's no hope. I actually have run into that more than a botched NR job. Almost as annoying-but at least fixable are those where the whole show needs a 300% volume boost-and I've DL'd plenty of those. The way I try to do it-up what is first rate. If something seems scarce-yet what I have really is flawed...odds are a better version exists,and often it appears on a bt site. Later-after I do the next puter,with a better soundcard-I'll hunt through my analogs and see what still has not appeared online. Already several have shown up-and in better quality. A few probably won't appear until I digitize them.

A note-it is VERY important that if you try to remaster/clean up audio files you have GOOD speakers...not "computer " speakers,but a real stereo amp and some quality,accurate,monitors. :wave:

guygee
2005-08-14, 11:21 PM
Actually-a big peeve of mine is torrents put out with major clipping. Some of these were recent vintage,from DAT so analog hiss is no factor,but somewhere along the line the waves got major clipping. A few clips are fixable-but if the whole thing is maxed-there's no hope. I actually have run into that more than a botched NR job. Almost as annoying-but at least fixable are those where the whole show needs a 300% volume boost-and I've DL'd plenty of those. The way I try to do it-up what is first rate. If something seems scarce-yet what I have really is flawed...odds are a better version exists,and often it appears on a bt site. Later-after I do the next puter,with a better soundcard-I'll hunt through my analogs and see what still has not appeared online. Already several have shown up-and in better quality. A few probably won't appear until I digitize them.

rerem - I think that this is a very good point to make. I have run into many recordings that are ruined by clipping, and really no way to recover the music, only some "peak-rounding tools" that yield far from perfect results.

There are several different causes of clipping. In analog recordings, the pre-amp (like any amplifier) has a linear range relative to input level, and beyond that a non-linear range where distortion is introduced. A good piece of analog recording equipment should have a VU meter that calibrates 0 dB to the top of the linear range. If recording levels go just a little above the calibrated optimum, distortion is introduced. Low levels of distortion might actually sound pleasant to some people's ears, adding a kind of warmth, but if the levels get too high then the sound becomes nasty and the recording is ruined in those parts. One might refer to this as "analog clipping". I think "analog clipping" is also referred to as "overdrive" or "over-saturation", and it leaves the recorded waveform rounded but distorted compared to the actual waveform of the input. I do not know of any "cure" for this, maybe someone out there can point to some tools that can help recover from this type of problem?

More pertinent to our discussion here is digital clipping, where 0 dB represents the maximum level that can be represented with any given n-bit digital recording.

Digital clipping occurs when you have exceed the maximum sound level that can be represented (in binary, either 16 1's for 16 bit formats or 24 1's for 24 bit formats). Digital clipping completely flattens the waveform, which introduces some very nasty distortion, so it absolutely must be be avoided.

Digital clipping can occur in the digital recording process, in A/D'ing an analog recording, or in the process of "remastering" a digital recording.

One example is A/D'ing an analog cassette - if your preamp levels are set too high you can introduce clipping. One of my A/D units, a Motu 828, has a warning light that stays lit if I clip even a single sample. It is a 24bit-48 kb/s unit, and I figure that I am just "wasting bits (not using the full dynamic range) unless I set my input level "just high enough" so that it is at the maximum level that will not introduce clipping. In practice, this means I set my levels and A/D, then tweak my input levels up and re-A/D, repeating until clipping occurs, then tweak the levels back down "just enough" and do the final A/D conversion so that no clipping occurs. This is the only way I can figure to take advantage of the full dynamic range that 24-bit offers. If the recording is clean and well-balanced (no drop-outs, no warble, no speed correction needed, etc), then the only only other operations I will perform is to remove DC bias from the untracked (large) wav file, and normalize the entire show at once "by peak" (not compression!).

I think that what some people do not realize, when they are attempting to remaster a show, is that many operations increase the levels and can potentially can cause digital clipping. For example, any kind of active filtering (which can include some NR algorithms), dynamic equalization, and poorly-implemented compression are some examples (to add to the discussion, maybe somebody can point out other operations that change levels?). If you plan to perform these types of operations, leave yourself some "digital headroom". Most decent audio remastering software will have a utility to check for digital clipping, so this should be run after any other operation is performed, and at the end of your remastering effort before tracking, just to be sure.

As a related aside, I hate it when folks normalize "by track" instead of "by show". The relative dynamics between the tracks from a show should be preserved, because some songs are meant to be "soft and sweet" while other songs are meant to be loud. If you normalize by track, you are subverting the true intentions of the artist or band when they performed the show, and if you didn't document exactly what you did, there is no going back, so your version of the show is in a sense "polluted" forever.

guygee
2005-08-15, 07:37 AM
(Note to self ;) ) Even the operation "Remove DC Bias" can cause digital clipping. I always remove it because I figure it is an artifact introduced by the recording gear, but since it shifts the whole waveform up or down, it can clip off "wavetops" in the direction it is shifting the waveform.

And using the "replaygain" tags in flac files and editing them to your liking can eliminate the need for a final normalization, but you still have to find the right levels when A/D'ing from analog sources.

Lou
2005-08-15, 08:12 AM
Maybe the shows that have digital clipping were recorded with the volume too high to begin with? In which case there's nothing you can do about that, that's how the source is.

With analog cassette>digital transfer, however, there should not be digital clipping other than maybe an occasional pop, whistle or clap.

guygee
2005-08-15, 09:47 AM
[...]The way I try to do it-up what is first rate. If something seems scarce-yet what I have really is flawed...odds are a better version exists,and often it appears on a bt site. Later-after I do the next puter,with a better soundcard-I'll hunt through my analogs and see what still has not appeared online. Already several have shown up-and in better quality. A few probably won't appear until I digitize them. [...]

rerem - (You probably already know this, but for the sake of others who are new...)When you build your next computer, try and go with a soundcard with a "Stand-Alone" A/D convertor. Prices have gotten pretty reasonable on these. You do not want the analog signal entering your computer case, there is all kinds of nasty noise inside of there, and it will show up in your recordings. Doing the A/D outside, in a shielded seperate box, eliminates that problem.

Like you, I have a lot of cassette recordings, but all of unverified lineage. I keep waiting for better sources to come out, but cassette tapes do not last forever, they become increasingly demagnetized, so hiss increases with age.
Many of these shows are not circulating, so it makes me think maybe I should get on with the job. If better sources emerge, people could always just trash my version. But since it is a lot of work to do a good job on even one show, first I think I would 1) Re-listen and start with the best sounding shows that don't circulate in digital form, 2) "google hard" and try to trade-up to get multiple copies and see if anything better is out there. I would probably want multiple copies anyways to use as patch material if my copy has any drop-outs, cuts or other flaws that were introduced somewhere after the master recording was made.

guygee
2005-08-15, 10:29 AM
Maybe the shows that have digital clipping were recorded with the volume too high to begin with? In which case there's nothing you can do about that, that's how the source is.

With analog cassette>digital transfer, however, there should not be digital clipping other than maybe an occasional pop, whistle or clap.

I am curious, what is the manufacturer/model of your A/D unit? I have both a Motu 828 24/48 and a M-Audio Duo 24/96. Both of of these units have input level controls that you have to set yourself (e.g. you have to twist the knobs to the correct settings). I can guarantee you, from personal experience, that if you set the input levels too high on these units clipping does occur, the Motu unit even has that warning led that tells you that you have clipped. If I set my input levels to full setting, massive clipping will occur on anything but the weakest input signal (any such analog recording would be very poor, very much lacking in dynamic range).

Maybe your unit has some sort of "input level limiting" feature that prevents clipping? I do not think I would want to use such a feature, because the peak amplitude values are different for each analog recording, so such a feature could easily result in unintentional compression. I would rather have control myself, and I do not want to compress any shows.

I would be interested to know if there are any other methods to prevent clipping when A/D'ing a cassette, but I cannot think of any other possible ways other than what I mentioned above. With my A/D units, setting levels is just like what a taper has to go through, except the taper gets only one chance to get it right, while I can tweak to my heart's content until I get it just right.

freezer
2005-08-15, 01:37 PM
RE: this thread and the current seed on TTD of the Entwistle "rough mixes" from 7/18/79...

Just so it's known, I mastered the Entwistle 7/18/79 rough mixes from a cassette which is now the furthest back the material can be traced in that format. (I have no idea if the 2" master multitrack reels still exist. OR if any of the multitracks were re-recorded.)

The Rough Mix reel for 7/18/79 was destroyed soon after my cassette 1G copy was recorded. (Any remaining tapes from that bankruptcy sale were sold as blank reels after being bulk erased.)

The 1G cassette was recorded too "hot" and does have some flaws, so I made 3 different digital transfers and sent the discs out to three different seeders for offering on three different sites.

Each transfer is slightly different.

However I used no digital noise reduction on the set offered at TTD.



If the seeder A/D'ed from an analog source, or from a rare/uncirculating digital source, and applied NR processing, then I think it would be fair if the seeder would offer, upon request, to distribute the raw source in the original form (hopefully 24 bit/high sampling rate) to any person claiming the experience to do a better job, or to anyone offering to archive the files on a publicly accessible site.

Your opinion only. Others may not agree.

Your mileage may vary.

Lou
2005-08-15, 01:59 PM
I am curious, what is the manufacturer/model of your A/D unit? I have both a Motu 828 24/48 and a M-Audio Duo 24/96. Both of of these units have input level controls that you have to set yourself (e.g. you have to twist the knobs to the correct settings). I can guarantee you, from personal experience, that if you set the input levels too high on these units clipping does occur, the Motu unit even has that warning led that tells you that you have clipped. If I set my input levels to full setting, massive clipping will occur on anything but the weakest input signal (any such analog recording would be very poor, very much lacking in dynamic range).

Maybe your unit has some sort of "input level limiting" feature that prevents clipping? I do not think I would want to use such a feature, because the peak amplitude values are different for each analog recording, so such a feature could easily result in unintentional compression. I would rather have control myself, and I do not want to compress any shows.

I would be interested to know if there are any other methods to prevent clipping when A/D'ing a cassette, but I cannot think of any other possible ways other than what I mentioned above. With my A/D units, setting levels is just like what a taper has to go through, except the taper gets only one chance to get it right, while I can tweak to my heart's content until I get it just right.

I actually don't have any taping gear, I go to at most 2 concerts a year, it's just not worth spending hundreds of dollars to buy something when the likelihood is high nowadays that I'll be able to trade for it.

Converting analog cassettes to CDR however, I have a Sony RCD-W500C standalone burner which has a VU meter, letting you know immmediately if it's clipping. I always edit everything I transfer with Soundforge so I'll see the clipping there as well.

So I'm not talking from experience, but it's just something to consider that maybe the taper set the levels too high, so it's clipped not because some bozo edited it and made it that way, but because that's how it was taped.

guygee
2005-08-15, 05:40 PM
I actually don't have any taping gear, I go to at most 2 concerts a year, it's just not worth spending hundreds of dollars to buy something when the likelihood is high nowadays that I'll be able to trade for it.

I am considering getting some gear, despite the cost, because I have become really pissed-off at myself for not having taped some of the really good shows I've seen in my lifetime that will never circulate, like John Hartford solo, tap-dancing on a piece of plywood in a Pittsburgh pizza parlor (late '70's), or like Gregg Allman, surprisingly burly, who showed up at a tiny bar around here (EC FL coast) and jammed with some blues guys for awhile. A couple of years ago, I tried to trade for the 1986-07-03 Petty-Dylan-Dead show that my brother and I saw together so I could make a really nice birthday gift for him; all I could find after months of searching was 3 copies, no lineage, all pretty high-gen (yes, NR was applied to my "remaster"). I sent out about 50 offers, so I guess my list just wasn't good enough, despite being fairly large. I've never seen the show torrented either. Too bad for me I didn't have the Master's of all those shows I'd seen in my life...


Converting analog cassettes to CDR however, I have a Sony RCD-W500C standalone burner which has a VU meter, letting you know immmediately if it's clipping. I always edit everything I transfer with Soundforge so I'll see the clipping there as well.

So I'm not talking from experience, but it's just something to consider that maybe the taper set the levels too high, so it's clipped not because some bozo edited it and made it that way, but because that's how it was taped.

I'm just starting to research the newest technology in taping gear, so I am not talking from experience either, but I know with older shows tapers had to set their levels, and some of them set them too high, you can hear the results in their recordings, so I agree with you here.

But the clipping can also come from someone is careless (with your unit or mine) and doesn't watch the preset levels and/or the VU meter every second, and then clipping can occur (major clipping). At least you know you can check for clipping in Soundforge, newbies might not. And even if the newbie finds the clipping, will he go back and start from scratch, or will he use that little "peak rounding" tool to fake it and think he just did a "good job"?

The point I was trying to make earlier is that, at that one moment when the show hits its highest peak, you want your VU meter on your Sony RCD-W500C to "almost, but not quite" touch zero dB. For 16-bit units that holds true (well it also depends on the noise floor level of the cassette) but for 24-bit, maybe it is overkill since 24-bit has more dynamic range than even the cleanest cassette (127 dB vs. 90 dB sound about right?)

guygee
2005-08-15, 06:34 PM
[...]
The Rough Mix reel for 7/18/79 was destroyed soon after my cassette 1G copy was recorded. (Any remaining tapes from that bankruptcy sale were sold as blank reels after being bulk erased.)
[...]

I went through a time when I bought a lot of unknown reels on ebay, sold as blanks. Maybe I have these? Then, just like on "CSI Miami", I could use special "magnetic ghost recovery software" and recover these shows?

Life is too short...

Thanks for the very nice seed, freezer.

freezer
2005-08-15, 07:51 PM
I went through a time when I bought a lot of unknown reels on ebay, sold as blanks. Maybe I have these? Then, just like on "CSI Miami", I could use special "magnetic ghost recovery software" and recover these shows?

Life is too short...

Thanks for the very nice seed, freezer.

Life's too short to chase after the same show a dozen times looking for the 'best sounding version'.

Better to waste your time recording shows with a realistic mono cassette recorder from PBS Lite Jazz in the Morning.

And you're welcome. 8 more to come at here at TTD and more on other torrent sites.

And I'm breaking out the Sound Forge this evening for a work-out on Who Biloxi 1982-12-01. :lol :lol :lol

Lou
2005-08-15, 09:59 PM
I was basically referring to say someone taping with a DAT machine who set the levels too high. If that happens you'll see digital clipping.

You should never see digital clipping though from an analog source...even if it's distorted on the tape, it doesn't have to be distorted on the digital transfer too.

Five
2005-08-16, 11:55 AM
clipping can also be intruduced thru an ANA > ANA transfer.

best thing to do is record a bit at a safe level which is too low, zoom in on the peaks and see what clipping exists on the master. then crank it up slowly, each time checking if the peaks are still okay. back it up a couple db from the top and run the whole tape.

and watch out. vu meters look cool and everything but they're averaging meters and won't always show momentary spikes. give a gander in a wav editor to really see how good your transfer is. Also, compare with your ears. Something is always lost, but you can minimize that by cross-checking frequently.

el c
2005-10-14, 01:05 PM
A couple cool links re: clipping and dynamic range issues. Important for the fixer-uppers out there and an interesting history of professional CD engineering.
http://www.mindspring.com/~mrichter/dynamics/dynamics.htm
http://www.cdmasteringservices.com/dynamicrange.htm

mort
2005-10-18, 09:31 AM
from experiance i have found if you master at 48 khz 24 bit you will not get as many digital artifacts from noise reduction !

as for what to use i reccomend waves x-noise !

tomska
2005-11-02, 02:10 PM
To add my opinion, i often use soundforge to clean or boost a recording this is for my soul benefit,i will never corrupt the origional source which can be passed around the pool,as is.The saying "a little knowledge is dangerous"rings true.I consider myself to be quite good at remastering but who am i to make such an arrogant claim? It's all down to horses for courses, i weld lumps of metal together for a living, thus i'm no studio engineer,and i never will be,but there are people out there who think otherwise.I say leave the trickery to the experts.Never corrupt the master.

Malth
2006-01-12, 07:57 PM
Yes noise reduction can be done shitty, but using quality software, such as wavelab with its very good noise reduction, paired with a pair of good headphones, can yield positive results

EddieHill
2006-01-14, 05:09 AM
I tried noise reduction with wave pad. Some stuff it works on . Others it is weird it made the song start and stop while I was playing it in my media player. The best thing that works for me is to play the music through my EQ.

darkstar67
2006-01-31, 04:21 PM
Digital Noise Reduction can make a terrible sounding tape sound great.

I am a recording engineer. I work for people like Oteil Burbridge and many others. Goldwave is NOT the way to go in my opinion, I actually LIKE Magix Audio Cleaning lab but that is just because they make the GUI so easy.
the same "fixes" are available from WAVES whon I highly recommend. I wish izotope would come out with a NR... Ozone is the best plugin out there... :clap:

OU812
2007-02-26, 06:22 PM
http://audio-restoration.com/cassette.php

IWishIWasBlank
2008-04-29, 05:15 PM
Great thread. I'm a radio DJ (ie: amateur sound technician) but totally anal about recordings we perform. Like it has been stressed, don't do noise reductions unless you know what you're doing. I've always likened overdoing it to talking through water.

pfreitas
2009-06-30, 09:46 PM
hummmm nice hehehe

thnks for the info =D

PencilGeek
2009-10-11, 03:00 AM
Back in the early days of NR software, often times the results were worse than the original noise. Many years ago, Sound Forge introduced NR 2.0 plug-in with a big fanfare, and charged $200 for the privilege of using it. At the time, I liked it a lot. Then a few years ago, I began lurking on Zappateers.com -- after somebody told me there was a discussion about one of my master recordings -- FZ 1980 12 11 (E), partial show -- the Nakamichi recording. As a lurker, I read the thread about my recording and saw the CD I had mastered many years ago was rejected as a source for their "official shows" -- because when it was placed under spectrum analysis, one could see all sorts of frequency banding caused by the NR software.

That was a HUGE eye opener to me. I'm a perfectionist by nature, so I couldn't tolerate that type of adverse side-effect caused by the NR software. At that time in 2007, I was already in the process of remastering this same FZ 1980 12 11 show using some newer software and prepared to release it in 24/96 resolution. I was also preparing to embark on my most ambitious remastering -- a very special Stevie Wonder concert from 1983. The Stevie concert was the real gem, a concert so unique and special that I considered it a cost-no-object project. (It ended up being that way too: $2000+ in new software/hardware and 300+ hours behind the computer remastering the show.)

The time was perfect to look for new NR software -- and it turned out that I was in the right place at the right time. I don't remember how I made the discovery, but I found that iZotope had just released a new product called RX -- Noise Reduction software. I had never heard of iZotope before this, but I was intrigued by their description of the product. They claimed they threw away all of the old school assumptions of how NR software should work, sat in a room for a year, and invented a completely new and unique way of approaching NR. Believe it or not, that's exactly what I was looking for -- throw away the old school, and start from scratch with a new book. For the first 30 days, they ran an introductory special price offering standard RX for $200 instead of the $350 MSRP. Also of interest was RX-Advanced, a $1200 version of the same software -- albeit with more knobs exposed for the user to tweak, plus ground breaking algorithms for downsample and dither (these two features are not available in standard RX).

For $200, I figured I didn't have anything to lose so I bought it. First trial: I was absolutely amazed. The noise reduction capabilities exceeded my wildest imagination -- and best of all, it didn't cause any frequency banding! I liked it so much, I wanted to purchase the full RX-Advanced version -- but there was one problem: they didn't offer an introductory discount -- they wanted the full $1200. I tried, and tried, and tried (even got in an argument with them) about offering an introductory UPGRADE to people who had just purchased RX. They offered me a $200 credit, but they weren't budging at all on lowering the price. But in the mean time, and in midst of arguming with them, I was finding bugs in their UI, reporting them, telling them how to reproduce it, and even making very solid suggestions how to make it better. They ended up liking my ideas so much, they made me a beta tester, and gave me a free upgrade license to RX-Advanced!

I know how many of you feel about noise reduction. But I'm here to tell you a new era of noise reduction has been born. So to prove this, today I took an 8-minute section of one of my shows and did a before/after FA and SA comparison.

Here's a spectrum analysis and frequency analysis of the original source material:
http://www.rcollins.org/concerts/images/SA_PreNR.jpg
http://www.rcollins.org/concerts/images/Cassette%201A-RAW-Log.jpg
http://www.rcollins.org/concerts/images/Cassette%201A-RAW-Linear.jpg

Using RX-Advanced, I imported a sample of my noise print. The noiseprint was taken from the section of tape during Easy Meat -- the section I had accidentally erased 20+ years ago. Then using the following settings, I applied the noise reduction. To see the difference between RX ($350) and RX-Advanced ($1200), the knobs appearing below "Less<<<" are only available on RX-Advanced. I came upon these settings by studying the manual, and significant experimentation. More than 95% of all of my uses, involve these exact settings. Only in the most extreme cases am I forced to change these settings to something else.

http://www.rcollins.org/concerts/images/NRSettings.jpg

Now let's look at those same images after running the noise reduction:
http://www.rcollins.org/concerts/images/SA_PostNR.jpg
http://www.rcollins.org/concerts/images/Cassette%201A-NR-Log.jpg
http://www.rcollins.org/concerts/images/Cassette%201A-NR-Linear.jpg

You can see from the spectrum analysis that the noise is completely gone, and RX didn't create any banding whatsoever. So as the final test, let's compare the Frequency Analysis. The best way to make the comparison is to capture both images in an image editor. Let's assume you've opened one of the "RAW" (pre-NR) graph. Using an image editor, only select the graph and "copy" it. Open the same NR graph, and paste the selection right over the existing graph. Then using the UNDO and REDO buttons on your image editor, see how the graphs have NOT changed -- except for the noise itself. The noise floor is lower, but the frequencies and their relative amplitude are all still completely intact.

In this demonstration, I hope I put to rest the notion that all NR software can't be trusted. The images I presented above demonstrated that NR is possible without banding or other damaging side-effects.

While I'm talking about RX-Advanced, I wanted to mention some of the other features as well. The spectrum repair is basically useless for live recordings. By contrast, I do use the spectrum editor with great effect to remove coughs, chair noise, microphone muffling, tape drop-outs, etc. The hum removal feature can be very useful, but very few recordings actually have hum on them (caused by the instruments, not my equipment). The only other feature worth mention, is the downsample and dither capabilities. Downsample and Dither are features only available on RX-Advanced -- the $1200 product. According to these two white papers, iZotope believes they've come up with a substantial advancement in downsample and dither as well.

http://www.izotope.com/tech/src/
http://www.izotope.com/tech/mbit/

A valuable guide to determine if that claim is true, is the following test lab site: http://src.infinitewave.ca/. If you compare the iZotope downsample and dither results to all of the others, you will see they are in a class of software that is so good, only one or two others even come close. Based on this web site, I'd say that these algorithms are in the top-5 best downsample and dither algorithems. And when you compare the top-5 to all others, you'll understand what I mean when I say they're in a class of their own.

The reason I mentioned this advanced downsample and dither -- wasn't to encourage a group buy of $1200 software. On the contrary. The new Sound Forge Pro 10.0, licensed these algorithms from iZotope, and they are now part of Sound Forge!

Ziggzzster
2009-10-13, 07:38 PM
Yep, you can definitely butcher recordings if you don't know what you're doing. I recently tried some "hiss reduction" presets in Goldwave and Cool Edit. I was pretty shocked when I checked out the frequency analysis - Goldwave would easily pass as lossy!

Attachments:
Original
Goldwave
CE

pissah
2009-12-06, 11:14 AM
I haven't uploaded any torrents here [I have on Dime under my Dime ID] but I usually only use a little light EQ on the high end to deal with hiss, if you over-do it you begin to cut muscle along with the fat.
Since I grew up with vinyl I learned long ago to tune extraneous noises out so a little hiss doesn't bother me.

pissah
2009-12-06, 11:16 AM
Yep, you can definitely butcher recordings if you don't know what you're doing. I recently tried some "hiss reduction" presets in Goldwave and Cool Edit. I was pretty shocked when I checked out the frequency analysis - Goldwave would easily pass as lossy!

Attachments:
Original
Goldwave
CE

Yes - I've had that problem even with very minimal EQ-ing - WAV files can look like mp3 in these analyzers.

lordsmurf
2010-03-21, 01:59 PM
Going back to the very first post -- there are way to remove that metallic/glassy effect. Goldwave is the most common cause of that. There is an anti-"Electronic Noise" filter in this SoundForge filter presets pack (http://www.digitalfaq.com/forum/showthread.php/soundforge-audio-filter-1605.html) that often helps.

Restoring audio is not easy. The most common way to filter it to carve out the unstable/noisy frequencies. There are definitely trade-offs for this. Some of the "counter frequency" methods can work too, although they tend to leave odd digital noise artifacts behind. I'd also remind everybody that restoring is about "making it better" and not "making it perfect". Even the most expensive and specialized forensic software can have trouble with some types of noise.

For working with audio, I suggest SoundForge, Audacity, Goldwave (in limited usage only), and DiamondCut Forensic. I'm not a big fan of Izotope. Many years ago, DartPro was also pretty decent. There are other options. While I didn't see it mentioned in above posts, I disagree that Pro Tools is good for restoring audio -- it's just a fancy editor.

You also need good speakers.

If the source is analog, run it through mixing boards first, to pre-process it. Some things just sound better fixed through hardware.

lordsmurf
2010-03-21, 02:11 PM
I saw an older post that mentioned clipping. I had a project just yesterday where the audio values on the source tape were already clipped. I corrected the loudness through a mixer, and then further removed the clipping artifacts with filters in SoundForge. Those presets are also included in the filters download (http://www.digitalfaq.com/forum/showthread.php/soundforge-audio-filter-1605.html) mentioned in the last post. I slightly tweaked the values for my own needs, I didn't use the preset exactly. Learning how to build your own filters, or tweak others, is really the key to doing good work.

There's a similar recent discussion on fixing clipping at this audio/video filtering forum (http://www.digitalfaq.com/forum/showthread.php/filters-cracking-sounding-2073.html), too, with examples. That person had some kind of tape that was captured too loudly, and the levels were terrible, with crackling audio.

Audio compression also adds noise, especially as you crunch down the bitrates. It varies from format to format. So don't compress restored audio too much, or you'll just end up adding new problems.

Just wanted to add my input to this good conversation. :)

AliveIsDead
2011-03-31, 11:34 PM
glad i stumbled into this topic.. being new i extracted audio for dvds and have been wondering how i can improve the sound and i gather from eveyones expertise it's best to leave it alone. i do manipulate the audio but only for my own understanding in what's involved. i've demuxed the audio then re added it. some have worked out and some sounded like a psychotic butcher had his way with it. never changing filetype or bitrate tho. i use izotope software mainly to denoise tho that's about as far as i can go without degrading the audio. at first i was very aggressive but have since learned to let my ear judge. nothing at all wrong with doing this for your own experience but like so many have said already if it's something for seeding or trading it's best not to mess with audio or video at all.

jpeace
2013-02-04, 05:27 AM
I'm with PencilGeek on this one. Izotope Rx is the way to go when doing NR. It it the most sophisticated of the easy to find (read: free if you know how) tools and does the least damage to the original recording while removing, in some cases, a huge amount of unwanted noise.

I am one of the team that restored the Pink Floyd Zabriskie Point music. Listen to the versions of Oenone and Rain In The Country on the MQR release, then compare those to all previous releases. You will see that digital NR can be done right