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Spectral Correction With Samplitude

Samplitude Tips & Techniques
By Martin Burrow

An entire Samplitude Pro X project can be shown in Spectral View by clicking on the icon at the bottom.An entire Samplitude Pro X project can be shown in Spectral View by clicking on the icon at the bottom.

Among Samplitude Pro X's unique features is spectral editing in the main project window. Here's how it works.

When you're working with audio from a live performance, it's not uncommon to encounter unwanted noises such as the creaking of a piano seat, accentuated finger noise on a guitar fretboard, lip clicks, car horns, and headphone bleed from click tracks. This is when Samplitude's Spectral Editing can be of great assistance, representing your audio on screen as a spectrogram and allowing you to pinpoint these offending short-duration noises visually, before selecting with a special mouse mode and removing them. The underlying musical frequencies are then recalculated and rendered as a seamless edit.

It's possible to display all the audio within a Samplitude Pro X project in Spectral View: to turn Spectral View on or off globally, click the Spectral View toolbar icon, which is at the bottom of the VIP, or press 'Y', navigate to Design / View Options and tick the Spectral View box near the bottom right-hand corner. Immediately below is a menu where you can choose how the resulting spectrogram is represented. You have a choice between default, halve, high resolution, black and white, red or blue. I find the default setting works well, as it lets you view the different frequencies based on colour, making it easier to spot unwanted artifacts. When you've made your display choice, press OK to exit the View Options. Depending on the size of your project, you may find initially that there is a slight delay while the objects are updated. All audio files will now be switched to Spectral View, with a smaller version of the original waveform also shown above each spectrogram. In the case of stereo audio files, this spectral view will be split into left and right sides, giving you the extra flexibility to edit out noises that are on just one side of the stereo image.

Spectral View can also be activated only for selected objects, from the menu item Object / Object Colour/Name / Spectral Display; alternatively, right-click on the object and, from the contextual menu, select Object Colour/Name / Spectral display. Obviously, if you're going to use this feature on a regular basis, it would be advisable to create a keyboard shortcut.

Here, I'm using Spectral View to remove a string squeak from a bass guitar part. Spectral Mouse Mode is activated from the Mouse menu.Here, I'm using Spectral View to remove a string squeak from a bass guitar part. Spectral Mouse Mode is activated from the Mouse menu.

In my first example, I'm going to use spectral editing to remove some unwanted string noise from a bass guitar note. If you look at my second screenshot, you can see that the bass line is represented as a spectrogram against a black background. Low frequencies appear near the bottom, high frequencies at the top. To begin with, you need to switch to Spectral Mouse mode from the menu item Edit / Mouse Mode / Spectral Mode. You can also access this mouse mode from the Mouse Mode drop-down menu in the main toolbar. Now all you need to do is left-click and draw a rectangle around the problem area. You can adjust this area using the handles positioned on each corner and at the centre of the vertical and horizontal lines. Once you are happy with your settings, click OK to confirm the edit. Changes will be quickly rendered and you can continue. If you decide you want to revert back, just Undo.

The Spectral Cleaning Editor

Although it's very convenient to have spectral editing available within the VIP, the degree of editing available is fairly basic. However, if you have the Magix Cleaning & Restoration Suite add-on, you will then have access to the Spectral Cleaning Offline Editor, which is much more fully featured. To open this editor, first select an audio object and go to the menu item Effects / Restoration / Spectral Cleaning...(Offline), or right-click on the object and, from the contextual menu, go to Effects (Offline) / Restoration / Spectral Cleaning...(Offline). This will open the dedicated Spectral Cleaning Editor, which has an extended feature set compared to the basic in-line spectral editing.

The drawing tool (pencil) mouse mode will be activated upon opening the editor, and works in a similar way to Spectral Mouse Mode, as described above, but with some advantages. One of these is that you can draw multiple range selections, rather than just the single selection possible with the VIP in-line spectral editor. This is particularly useful when you have an audio object with several problem noises that need to be tackled in one go. After drawing a selection over an area in the editor, you will see three tabs at the top right. Clicking the top tab will remove the selection. Clicking the centre 'show original' tab lets you toggle between the original spectrum and the filtered spectrum, although this is purely visual, and has no effect on the sound. The bottom tab is the bypass button, which will let you hear the original, unprocessed signal.

When you first open the Spectral Cleaning Offline Editor, its calculation mode will be set to 'crossfade', but different modes are available when you left-click in the mode window. These presets include crossfade (hard), crossfade (from left), crossfade (from right), gap, damping, fade-in and fade-out. You'll notice that when you choose one of these presets, it will affect the spectral view of the current active selection. This can further be fine-tuned using the Intensity control. Moving this control affects the dry/wet ratio of the selected area. When it's set to the far left, no filtering will occur and you will only hear the original signal. The more you move it to the right, the more intense the filtering, until you reach 100 percent, which gives you the full effect. Notice, also, that as you change the Intensity setting, the spectral view of the selected area also changes. You will find the Intensity control works best if you use your mouse wheel.

Home On The Range

The term 'range selection' relates to the area selected using the drawing tool. If your audio has several similar clicks that need removing, the click markers can be very useful in speeding up this process. The audio in my third screenshot shows quite an extreme example from a vinyl recording, with a nasty scratch causing repeated clicks, all of similar duration and volume.

The Spectral Cleaning Offline Editor, showing several click markers with duplicated ranges. The centremost is bypassed, to show the click prior to removal — so you can see how effectively the other clicks have been dealt with!The Spectral Cleaning Offline Editor, showing several click markers with duplicated ranges. The centremost is bypassed, to show the click prior to removal — so you can see how effectively the other clicks have been dealt with!

It would be time-consuming to have to draw a range over every click, so I have begun by adding click markers. To do this, position the play cursor so that it bisects the click, and left-click on the middle of the three yellow marker icons at the top centre of the Spectral Editor or use the keyboard shortcut Shift-C. To place the markers with greater accuracy, grab the magnifying glass tool from the top left of the editor, left-click and draw a box around the area you need to zoom in on. Right-clicking restores the zoom. All click markers will be labelled with a 'C'. Note that if snapping in the VIP grid is engaged, markers will snap to the grid unless you hold down the Alt modifier.

Next, draw a range around one of the clicks; to check that you've drawn round all and only the problem area, A/B using the Bypass button, and try ticking the Play Inverse box at the bottom, to hear just the processed signal. This can be very useful when you're adjusting the selected range. You may also need to experiment with calculation and intensity settings, although in my example, the default 'crossfade' mode and resolution of 256 seem the most effective. The next step is to left-click on the yellow 'Apply range selection to all click markers' icon, which is above the Insert Marker icon. Now the range will be duplicated to the positions of the other click markers. It is also advisable to tick the Create Copy box, as this ensures that the rendered file is saved as an FX file. Finally, press 'Calculate' and you're done.  

Cleaning Materials

For the more advanced restoration techniques described in the second half of this article, you'll need the Magix Cleaning & Restoration Suite, which includes the Spectral Cleaning Editor plus real-time De-Clicker/De-Crackler, De-Clipper, De-Noiser and Brilliance Enhancer. These are proprietary plug-ins which are built into Sequoia 12, and available as a paid add-on for Samplitude Pro X.

pro.magix.com/en/samplitude/cleaning-restoration-suite.524.html

Video Tutorial

For more on spectral editing in Samplitude Pro X, watch the video that accompanies this article at /sos/may13/articles/samplitudemedia.htm.

Published May 2013