What is a RXDATA file? Every day thousands of users submit information to us about which programs they use to open specific types of files. While we do not yet have a description of the RXDATA file format and what it is normally used for, we do know which programs are known to open these files. IZotope RX 4 Explained. IZotope RX 4 is here and iZotope guru Mike Thornton (Mr RX It) delivers everything you need to know to jump into RX 4 and harness its full potential! Get detailed information using real-world examples and clean up your recordings making them sound better than ever.

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With their hefty low–frequency content, vocal plosives are obvious as the blobs at the bottom of the spectral display.

The latest version of iZotope’s RX adds some interesting features — but do they have musical applications?

Restoration software of a kind which is relatively easy to use and which gives decent results is a comparatively new sector of the music software market. Someone will tell me that the DeNoise module in Sonic Solutions was probably in the vanguard here, but my own first encounter with this class of tool was CEDAR Retouch, fitted as an optional extra in the SADiE system which we used to record, edit and master classical recordings a decade ago. It was expensive, but invaluable: recording engineers’ nightmares such as piano pedal thumps, piano stool creaks, even lip smacks and the occasional cough no longer demanded a re–take, but could be eliminated, or substantially reduced, in post–production.

I originally bought iZotope RX2 to do some fairly heavy restoration work on a series of 1970s live operas that I was remastering for issue on DVD and accompanying CD. Sod’s Law dictated that the job came in just after I’d sold my SADiE system, and the built–in Spectral Cleaning facility in Magix’s Sequoia could not do all that was needed. Other offerings were beyond the budget, so RX2 fitted the bill perfectly, and I still think that the Advanced version is a whole lot of professional software solution for a relatively small outlay. Only after those projects were completed did I begin to realise how tightly woven into my mastering approach it would become.

In For Repairs

I have now been using iZotope RX2 since it was released in 2010. Apart from the DAW itself, it is the one piece of software that I have found to be indispensable, and I have used it on pretty much every mastering session. RX can play almost any file, and has frequently opened recalcitrant formats which had standard DAWs flummoxed. It has exceedingly good sample–rate conversion (with MBit+ dithering) and, of course, it can repair sonic damage, ameliorating those bad–luck moments in live recordings and unnoticed horrors in studio recordings which cannot be recalled and undone. Even with projects that did not call for large–scale restoration work, it was good to be able to identify such momentary irritations as vocal glitches, the base of a mic stand being kicked, the studio cat, mic capsule distortions, clunks, coughs and so on, and quickly brush them aside. And that was only the Spectral Repair feature, which provides a highly informative visual interface for spotting and addressing these problems.

In my mastering suite, with its revealing acoustics and speakers with extended bass response, I often encounter vocal plosives and very fast transient clicks that have been missed by the client and the engineer. The pictures show how these look in the RX4 main display: the click is shown in Linear mode, as digital clicks have content across the whole frequency spectrum, while the vocal pop is shown in Extended Log mode because plosives have a great deal of low–end content. Each of these issues took just a few seconds to eliminate entirely in RX4: lasso the problem area, press ‘R’ for repair, and the offending item is attenuated to inaudibility. More complex problem sounds have more complex repair modes, but with a little experience, they are barely any more difficult to implement.

A rogue click is clearly visible in RX4’s spectral display.

It’s worth noting that iZotope present RX as software that can find application across all kinds of audio work. However, although many of the features of RX that I find useful when working with musical content are also useful for non–music audio work, the converse doesn’t always apply. In other words, there are some tools in RX which are very useful in non–musical applications, yet have less immediate use in music production. iZotope themselves sort the modules according to function, into Restoration, Production and Utility groups.

Three: The Magic Number

Late in 2013, iZotope released version 3 of RX. Not only did RX3 sport an entirely new, and very much more ergonomically optimised user interface, but it also included interesting new modules in all of the functional groups, and several previously Advanced–only features were incorporated into the much more affordable Standard version. As these included the excellent sample–rate conversion algorithms, this made the standard version of RX very much more attractive to a wider base of music engineers. Hugh Robjohns reviewed RX3 in full in the February 2014 issue (www.soundonsound.com/sos/feb14/articles/izotope–rx3.htm), so I don’t want to repeat too much of what was said then here, but it is worth re–emphasising the gist of the conclusion of that review, which was that RX3 is a worthwhile investment for anyone involved in professional music production, and that the upgrade from RX2 was also, as they say, a no–brainer.

In RX4 another advanced module, the Dialogue Denoiser, has made the same migration to Standard. iZotope are wise to have this divide, as not every engineer will need the Advanced–only functions, which are often quite specialised — and as I think the Advanced version is good value for money, this makes the Standard Version a bit of a bargain.

Pillar To Post–production

If RX3 represented quite a large leap forward from RX2, then RX4 is a smaller step in the same direction. New features include Clip Gain and a Clip Leveler, which do pretty much what their names suggest; less standard, and potentially more interesting, are features and modules such as RX Connect (see box), EQ Match and Ambience Match.

I mentioned earlier that some of RX’s existing features are targeted mainly at non–musical applications, and in fact, the two new modules in RX4 probably fall into this category. Ambience Match is not, despite the name, a convolution reverb, or indeed any kind of reverb. And while EQ matching — the idea of capturing the frequency responses of source and target tracks, and computing an EQ curve to make the former sound like the latter — arguably has a place in mastering and music production, the EQ Match feature in RX4 is so basic as to be of limited use. It is nothing like as sophisticated as Harbal (www.soundonsound.com/sos/feb13/articles/harbal-3.htm), nor even the Matching EQ feature in iZotope’s own Ozone mastering software. In the latter, the capture process produces visual curves for the overall EQ and difference EQ changes which can be overlaid to allow them to be compared and, if necessary, modified. EQ Match in RX is a greatly simplified form of this. The screenshot shows the UI dialogue, and the manual is quite succinct: after you have opened the EQ Match module, it tells you to “make a selection in a file; click Learn; make another selection; click Process.”

RX4’s EQ Match feature is more basic than its counterpart in iZotope’s own Ozone mastering software.

For musical needs, I would say that this implementation falls short of being really useful. Most music engineers would want much more information and much more control over EQ changes applied to their tracks. But as I’ve indicated, this module is probably more likely intended for certain non–musical applications where such immediacy (and very good results given the simplicity) is an advantage in itself. I can illustrate this better by introducing the Ambience Match module at this point and showing how they operated together when I revisited an audio–book project I worked on last year.

Voices & Choices

The main recording for the audio book, which featured a number of different voices, was done in a London hotel. But then sometime later editing changes were made to the text itself, and so certain passages of the book had to be re–recorded. Some of this took place in my own small studio in Norfolk, using the mic with which we’d recorded the originals; but one particular reader could not travel that far, so recorded the changes at a more convenient local facility with a different microphone and sent me the results to be edited in. At the time, this gave me an awful lot of extra work to do. There were clearly mismatches of vocal tone and also background ‘room tone’ (low–level ambient sound), and though I could EQ the vocal sound to minimise the differences, the only way I could make sure that there was no clearly audible difference in the rooms was to cut a small piece of room tone from the very beginning of the original recording, edit it to a usable length and mix it in, ducking it with the vocals. It worked just about well enough, but it took an awful long time.

For the purposes of this review, I revisited this nightmare with RX4 and it took me 15 minutes. Though the voices were the same, the use of different spaces, placements, mics and preamps meant there were tonal differences between the original and later recordings. The original recording was warmer and smooth, the re–recording to edit in was less so in both regards — but the RX4 EQ Match module made a very passable attempt to live up to its name, and I think I would have been happy to use the result had I had the chance to do so.

The new Ambience Match feature is designed to ensure that room tone can be made consistent when editing together recordings from different sources.

The room tone was very different between the two versions: although the original recordings were not exactly noisy, there was a very specific ‘hotel room’ sound to the silence, with a faint air–con motoring away somewhere in the basement. The re–recordings, made in recording studios, had much quieter, almost silent backgrounds, and this was easily perceptible when the original section segued into the edit. This is where Ambience Match came in. As you can see from the screenshot, it has the same minimalist interface as EQ Match. Fingerprinting the room tone from the original and adding it to new edits was very easy, and it took just a couple of experimental passes to get the level right. I had hoped that Ambience Match was going to be rather more — conceptually, it’s really just the Denoise module working in reverse, as the manual almost admits — but fitting horses to courses enabled it to show its proper strength. It also found a use in classical editing: many producers still insist that recordings do not fade to digital silence between movements and between separate pieces, so the editor has to edit in room tone recorded at the beginning of the session to give the illusion of a continuing live recital (ha!). Editing virtual silences together is a pastime for the seventh circle of Hell, so Ambience Match could be a real boon there.

Conclusion

As I have made clear, I find iZotope RX4 indispensable in almost every post–production project, including mastering and its manifold responsibilities. I also think the asking price is not a great deal for a professional facility to pay for a professional product, and that the ‘missing’ features of the Standard version that allow it to be offered pretty much at bargain price are less likely to be missed by music users. So RX4 is a great upgrade for users of RX2, and a great buy for those who are yet to feel the love at all. But is it a good upgrade for present users of RX3? I think it all depends on just how much use can be made by the purchaser of the half–dozen or so substantial new features. For those in film and speech post–production, this might be all of them; for some, like myself, who specialise in music but have a serious sideline in speech and restoration, that might be two or three; but for some music–only facilities, it might not be quite enough to justify the move just yet.

Only Connect

It is possible to use iZotope RX in two different ways: as an adjunct to a DAW, or in stand–alone mode. Even in RX2, there was already a facility which enabled Spectral Repair as a plug–in from within a DAW. In RX4 this has been replaced by a more fully featured ‘round trip’ capability called RX Connect. The idea is that, without leaving your DAW, you can either send a clip from your DAW for Analysis in RX (a one–way ticket) or you can send it for Repair and then return it to the DAW (a two–way ticket). One issue that can arise is that if your DAW does not ‘surrender’ its audio channels to RX when that is operating, then nothing routed through RX can be monitored. Enter an ingenious solution called RX Monitor, which gets around this problem by operating in the DAW as a virtual instrument through which the RX output can be played via the DAW’s non–surrendered channels.

I tried RX Connect in a mastering context, and it worked as advertised, but because there were a few menu items to negotiate and you need to pre-open the stand-alone version of RX, I found that it was just as easy for me to minimise the DAW, open RX in stand-alone mode, and work directly on the WAV file. Things changed dramatically, though, when I was working on a classical editing project where the fragments of music to be edited together were drawn from up to 100 different takes, hence 100 different WAV files. When doing this kind of work in the past, the technique I use now when mastering would not have been viable, as it would have meant opening all of those 100 different files, rather than the single one being worked on in mastering. Instead, I would deal with noises and suchlike by noting their time position in the overall piece, compiling the final edit and only then going to RX. It never occurred to me that there could be a better way — but this is where RX Connect starts to make much more sense. A process that is relatively unwieldy when compared to opening the stand-alone version for occasional work on a single WAV file becomes the clear winner when compared to opening and searching in 100 or more separate audio files! And also, as often happens, what seems a bit awkward when you are consciously concentrating on each step in the process becomes second nature and much easier as familiarity and muscle memory kicks in. Of course, there was a time when making up a DDPi file seemed like a lot of work..

Pros

• Better integration for those who like to carry out their restoration tasks within a DAW.
• EQ and Ambience Match can help when you need to edit together recordings made under different circumstances.
• Still offers excellent value for money.

Cons

• The new features are arguably more useful in post–production than in music work.

Summary

RX4 is a worthy update to perhaps the best–value restoration package on the market, though it perhaps won’t be an essential one for users who work only with music recordings.

information

In an earlier article I shared ways to approach restoring damaged sound effects. That dealt with ideas and perspective.

Today’s post will share more direct tips. I’ll explain practical tricks to help you get better results. I’ll start with general tips that can be applied to any restoration app. Toward the end, I’ll include suggestions specifically tailored to iZotope’s RX software.

General Tips

Be Aware of Tricky Sounds

Certain sounds are trickier to repair than others. Part of this has to do with the nature of the sound effect. Some of it has to do with the problem audio itself.

Consistent damaged audio is easier to work with. A steady thickness of noise, or pitch of hum is easier to identify, and to extract. The job becomes increasingly difficult the more this alters.

Some examples include cyclical problem sounds, like the swell and ebb of distant surf. HVAC and fluorescent light buzz seem constant, but actually cycle rapidly. Adjusting a microphone creates image shift, which varies the spread of audio abruptly.

Software may compensate for this with “adaptive” settings. Otherwise, expect a challenge.

What about the sound effect itself? Sibilant, swelling, and breathy sounds are more challenging to denoise. Aliasing may become more apparent. Also, drastic denoising affects these sounds more. Breathy sounds become thinner more quickly. Sibilant ones become especially slushy.

Sound effects with diverse dynamic are hard to denoise. Algorithms struggle to match big spikes of audio. Noise extraction follows a bit too slowly, resulting in a brief breath of noise after steep drops in audio.

Watch for these challenging sounds when you begin your restoration career. Set them aside for later, plan ahead, or tinker with better software.

Prepare For Restoration Early

I suggested mastering as you record sound effects last year. This is similar.

One of the most difficult aspects of restoration is finding a clean span of problem audio, called a noise profile. The noise profile is a “template” that tells the software what should be removed. The noise profile is a guide that divides the poor audio (the profile) from everything else you want to save.

This span must be separate from the sound effect you want to save. Why? A “clean” noise profile helps you analyze problems more easily. Also, if the sound effect overlaps a noise profile, you may mistakenly remove part of the audio you want to keep.

It’s easy to get caught up capturing sound effects. Often we’ll record rapid-fire takes. That results in scant space between your clips. That means there isn’t much free space to find a decent noise profile afterwards.

It happens when mastering, too. We’ll cut tracks tightly. That can be a problem when (sometimes years later) we try to denoise a sound and can’t find a clean noise profile in the track.

Record noise profiles in advance. You can do this by rolling tone before or after each take. I do this every time my microphone alters position, or when levels change significantly.

Save these profiles. Create presets in your plug-in or app. Save them to disk when mastering. That gives you a snippet you can reference later when mastering similar sounds. Label these clips with location, microphone, etc.:

Noise Profile, Garage at home, D50 at 120 degrees, Distant POV.wav

It also helps to leave a second before or after a sound effect when mastering. These “handles” help grab a good noise profile when repairing in the RX app, later. Then, when your track is repaired, simply chop off those handles.

Bonus: sound designer and field recordist Andreas Usenbenz of The Soundcatcher suggested another great tip via Twitter:

Record the self noise of your mics in a dead quiet room with different gain settings. Then use this as [a starting point to] denoise.

Preserve Your Work

Everyone knows it makes sense to backup your work before making big changes. This is important when restoring audio for another reason, too. Why?

Technology evolves. The tools available now didn’t exist five years ago. Denoising algorithms and decrackling tools become more sophisticated over time. Why does this matter?

I can still log into the account from other PCs and still access all PCs in the account (with the exception of this blocked one of course).Working on my own remote assistance app for Windows PCs (as that is 99% of my client use) just because I have always wanted to do one, and because I think people are hugely overcharged for remote assistance.I have tried cheaper remote assistance, but they have not been up to par as far as screen resolution, speed or simple things like file transfer.And I'd like to explore a 'pay as you go' model where you just pay for what you use. /teamview-lan-not-working-on-mac.html. This could mean a per-connection payment scheme or maybe a per-GB bandwidth usage scheme. You should be able to install the host application on as many PCs as you like - no charge. I just think remote assistance can be done more cheaply than TeamViewer while maintaining a simple UI, fast connections and a great looking resolution.A lot of the stuff in TeamViewer and LogMeIn is simply overkill for me. I need a fast connection, good resolution, file transfer, wake on lan and a way to tell me when antivirus (or other apps) need to be renewed.

Well, that rare Himalayan monk chant you’re struggling with today may be tidied up easily with the tools of tomorrow. Yes, audio restoration relies on the skill and ear of the technician. However, technology plays such a huge part of audio restoration that it’s a great idea to backup your damaged sounds.

I copy each file I’m denoising into a mirrored “Dry” or “Raw” folder. I append the file with the issue. For example:

Massive thunder blast_PEAK

Quiet Korean temple evening ambience_HISS

There’s no reason not to restore your audio now, of course. Sound effects are meant to be used, not buried in an archive. However, a backup is helpful to revisit your superstar recordings when new tools emerge.

Workflow

Change Bit Depth Of File Izotope Rx 3

Finish Similar Files At Once

I mentioned last week that restoration is done in “passes.” You’ll study small regions of a sound over and over.

As that happens, your ear will begin to “acclimatize” to the work. You’ll zone in on just that clip. That’s natural. You’re listening with incredible scrutiny. Your ear will develop a feel for the particular noise, hum, or the frequencies in the sound. You’ve developed that pass after pass as you adjust and strip away the problem sounds.

I find this kind of focus is incredibly helpful. That’s why it’s best to finish similar files all at once. It’s hard to resume that focus after a break.

Regain Perspective

While it’s best to finish similar files in batches, it’s a good idea to give your work space before committing it. It’s easy to lose perspective when you’ve been staring into the depths of noise profiles for hours on end. It’s easy to lose track of the scope of the whole file when you’ve been focused for hours yanking tenacious hum from your clips.

Did your restoration work improve the file, bruise it, or suck the life out of it? That’s why it’s best to step back. Ask colleagues for their opinion. I mentioned before that I master in “passes,” often over weeks. It’s important to do this with restoration work, too. Fresh ears spot errors.

Using iZotope RX

Newbies can be overwhelmed with the sheer amount of options in iZotope’s RX software. How do you begin?

The manual is good for facts. That describes the tools. What about context? It’s hard to know how, why, and when you should use the modules. Here are some tips to get you started.

Denoise: Fetch a Better Profile

Sometimes you find yourself struggling denoising a sound effect for the better part of an hour. You tweak settings, apply, listen, and it’s not quite good enough. You may hear a bit of musical aliasing, or slushiness. You undo your work, adjust, and repeat. It’s never quite right.

The solution? Fetch a better noise profile. In other words, often the sound itself isn’t the problem. Finding an cleaner, fresh stretch of audio from elsewhere in the file helps. That creates a better noise profile. Often the results improve instantly and dramatically.

If denoising isn’t working, start over with a noise profile from another part of the sound.

Don’t give up on noisy files. Find a better noise profile.

Denoise: Test Fragments

Denoising takes a lot of processing power. It doesn’t happen in realtime. That means restoring entire files at a time adds up. Check your work on a smaller region, instead. Where is the best place to do this?

Test your work on a variety of audio. Choose a region that includes consistent audio, dynamic, and a switch between them. That will test how your noise profile works behind quiet sounds, loud sounds, and areas without sound. Bonus: choosing a small portion also speeds your work.

Denoise: Split the Difference

When you first begin denoising, you’ll have no reference point. Should you choose conservative settings, or aggressive ones?

I begin denoising aggressively, listen to results, then reduce. So, I’ll start the Denoise Reduction slider at 12 (for example). I use that as a baseline. It may sound fine. However, less reduction is always better. That taxes the sound file less, and retains more of its original character. So, I’ll split the difference. I undo the processing, then try it again at 6. I’ll repeat, reducing or increasing the denoising until I find something suitable (to 9 if I need more denoising, or 3, if I require less).

During this process, I listen for errors being introduced, and gradually diminish the processing until I reach a balance.

You could work in the other direction: start conservatively, and gradually increase reduction. Then, when you start to hear aliasing, back off. That works, too. I personally find “working backwards” spots errors more easily.

Whichever you choose, discover the best settings by splitting the difference.

Denoise: Spot Gating

One of the sneakiest denoising pitfalls is gating. That’s when bursts or breaths of noise linger after sharp drops in volume. It’s almost as if denoising isn’t fast enough to sculpt tightly to the transients of your sound effect. It’s common in sounds with short, sharp attacks: door slams, gunshots, hits, drops, and so on.

Listen carefully to the audio directly after dynamic sounds. Does noise linger longer than it should? Do you hear a faint “chuff” or “exhale” of noise? That’s gating.

It’s easy to fix. Just adjust the “knee” and “release” when denoising. This can make the algorithm work harder, though, and may introduce musical artifacts. It’s a trade off. Find a balance.

Aside from aliasing, gating is the most common denoising error, but one of the hardest to spot.

Denoise: Leave Noise In

It’s easy to suck the life out of a sound clip. RX is quite powerful. It can extract every grain of noise from a sample. However, once all the noise is stripped away, the remaining sound effect will sound strange. It may become stark.

Removing all noise isn’t the goal when it eviscerates the authenticity of the file. Nobody wants lifeless sound effects.

Instead, leave some noise behind. I don’t mean an amount that overwhelms the original sample, of course. But given the choice between extracting all noise to create a lifeless file, and leaving a hint behind, do the latter. It avoids harsh processing, and may have the effect of smoothing out a clip.

Noise is one of a field recordist’s greatest enemies. Diminish it, but don’t loose sight of the quality of the sound. A “take no prisoners” approach to removing noise may make your sound effect sound unnatural, empty, and soulless.

Spectral Repair: Copy and Paste Spectrum

Spectral Repair is known for its Attenuate and Repair functions. There’s another trick I like better: copy and paste.

You’re probably familiar with copying and pasting in conventional editing apps. Copying a region of sound saves it to the clipboard. You can paste that same snippet anywhere else as many times as you like. When you do this, your snippet completely replaces what was there before. If you cut instead of copying, it simply removes an entire span of audio.

Spectral Repair works differently. Imagine a sparrow sings briefly during your room tone recording. Let’s say it’s song is at 500 Hz or so. Sure, that’s ruining your recording, but it’s only part of the spectrum. The other 19,500 or so hertz are perfectly fine, right? Why bother losing five seconds just to chop out a single, pesky chirp? Spectral repair allows you to fix just the bird chirp frequencies, and leave the rest alone.

Using Spectral Repair means you save your timeline. There’s no need to remove those five seconds of birdsong and lose the rest of the room tone, too. It may not matter as much for a room tone, but consider a jet pass. If you have to chop out the center of the pass to remove a problem, the fly by will be shortened, and may sound choppy.

Spectral Repair’s Attenuate and Repair functions can do this. This can also be done by copying a portion of the spectrum from elsewhere in the file, and pasting it over top of the problem sound. Only some frequencies are copied and replaced.

How can you do this?

1. Use the Time-Frequency Selection tool (CMD R) to select the frequencies around your bird chirp.
2. Drag your selection to a clean location elsewhere in the track.
3. Copy that section.
4. Drag it back over your bird chirp.
5. Paste. The bird chirp has now been replaced with clean audio.

A track with irritating squeaks

Zoom in on the squeaks

Select the squeak




Select an “empty” area

Paste onto the squeak




Normally traditional copying and pasting this way would sound terrible. The edits would be obvious. However, since you’re only pasting part of the spectrum, the rest of it tends to trick the ear.

Now, you’ll have to be careful. It doesn’t always work. The best results occur when there’s a consistent background. But when it works, it’s gold.

Find Errors

RX has a cool way to spot errors. When playing a sound, we’re used to listening to every frequency for a certain duration. RX allows us to hear just certain frequencies. How?

1. Choose the Time-Frequency selection tool (CMD R).
2. Choose “Enable Looping” (CMD L).
3. Choose “Play frequency selection.” You’ll hear only those frequencies you’ve chosen. So, you’ll only hear from 50 to 180 Hz, for example.
4. Drag the selection.

By dragging the selection you’ll be able to hear audio just in the chosen spectrum. It’s like scrubbing, but only certain frequencies. This helps pinpoint the location of elusive bird chirps, tones, or other problems. Most of the time you can spot this in the spectrogram. This is a good trick when the spectrogram is too muddy to spot errors visually.

Delete Your Work

And a final tip: if processing diminishes the authenticity of a file, even in the slightest, delete the entire track.

It can be hard to tell. Perhaps a sound is partially repaired, the most you can manage. Maybe it’s fully repaired, but feels lifeless. Neither of those produces exciting sound effects.

It’s painful to wrestle with a sound effect, and then abandon your work. It’s important to do, though. You won’t edit confidently with a weak library.

Polishing Your Sound Library

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Audio restoration is complicated, nuanced work. It’s a process of trial and error. It requires firm objectivity, and patience.

For all the effort and time it takes, it really is worth it. Audio restoration will rescue your precious field recordings. It will add that little bit of extra polish to make your sound library shine.

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