- Dec 19, 2018 iZotope RX 7: Spectral Repair Spectral Repair is a module available in iZotope RX 7 Standard and RX 7 Advanced audio restoration software that lets you remove and replace unwanted sounds and frequencies in audio.
- Available for download, iZotope RX 7 Advanced is the latest update to their audio-repair software, which is considered a staple within the recording, mastering, and audio-for-video, post-production communities. The software can operate either as a standalone.
Overview
Spectral Repair intelligently removes undesired sounds from a file with natural-sounding results.
RX 7 Help Documentation.
This tool treats selections within the spectrogram/waveform display as corrupted audio that will be repaired using information from outside of the selection.
Select the noise you want to repair and Spectral Repair will reduce it to the level of the noise floor, replace it with audio from around the selection, or generate entirely new audio to fit the selection.
Attenuate
This mode removes sounds by comparing what’s inside a selection to what’s outside of it.
Attenuate reduces spectrogram magnitudes in the selected area to match magnitudes from the surrounding area, resulting in the removal of the sound without leaving an audible gap behind.
Attenuate does not resynthesize any audio. It modifies dissimilar audio in your selection to be more similar to the surrounding audio.
Attenuate is suitable for recordings with background noise or where noise is the essential part of music (drums, percussion) and should be accurately preserved. It’s also good when unwanted events are not obscuring the desired signal completely.
For example, Attenuate can be used to bring noises like door slams or chair squeaks down to a level where they are inaudible and blend into background noise.
Attenuate: Controls
- BANDS: Selects the number of frequency bands used for interpolation.
- A higher number of bands can provide better frequency resolution, but also requires wider surrounding area to be analyzed for interpolation.
- A lower number of bands is ideal for processing short selections or transient signals.
- A higher number of bands can provide better frequency resolution, but also requires wider surrounding area to be analyzed for interpolation.
- SURROUNDING REGION LENGTH: Defines how much of the surrounding content will be used for interpolation.
- STRENGTH: Adjusts strength of attenuation.
- MULTI-RESOLUTION: The multi-resolution mode allows for better frequency resolution for the interpolation of low-frequency content and better time resolution for the interpolation of high-frequency content.
- BEFORE/AFTER WEIGHTING: Gives more weight to the surrounding audio before or after the selection.
- DIRECTION OF INTERPOLATION: Determines where the material used in the repair process is located in relation to the current selection.
- HORIZONTAL: Signal to the left and right of the current selection will be used for interpolation.
- VERTICAL: Signal above and below the current selection will be used for interpolation.
- 2D: Signal above, below, to the left and to the right of the current selection will be used for interpolation.Note: Direction Of Interpolation control availability
- Replace, Pattern and Partials + Noise tabs only utilize Horizontal mode and do not display this option.
- Replace, Pattern and Partials + Noise tabs only utilize Horizontal mode and do not display this option.
- HORIZONTAL: Signal to the left and right of the current selection will be used for interpolation.
Replace
The Replace tab can be used to replace badly damaged sections (such as gaps) in tonal audio. It completely replaces the selected content with audio interpolated from the surrounding data.
Replace: Controls
- BANDS: Selects the number of frequency bands used for interpolation.
- A higher number of bands can provide better frequency resolution, but also requires wider surrounding area to be analyzed for interpolation.
- A lower number of bands is ideal for processing short selections or transient signals.
- A higher number of bands can provide better frequency resolution, but also requires wider surrounding area to be analyzed for interpolation.
- SURROUNDING REGION LENGTH: Defines how much of the surrounding content will be used for interpolation.
- MULTI-RESOLUTION: The multi-resolution mode allows for better frequency resolution for the interpolation of low-frequency content and better time resolution for the interpolation of high-frequency content.
- BEFORE/AFTER WEIGHTING: Gives more weight to the surrounding audio before or after the selection.
Pattern
This mode finds the most similar portion of the surrounding audio and uses this to replace the corrupted audio.
Pattern mode is suitable for badly damaged audio with background noise or for audio with repeating parts.
Pattern mode is suitable for badly damaged audio with background noise or for audio with repeating parts.
Pattern: Controls
- BANDS: Selects the number of frequency bands used for interpolation.
- A higher number of bands can provide better frequency resolution, but also requires wider surrounding area to be analyzed for interpolation.
- A lower number of bands is ideal for processing short selections or transient signals.
- A higher number of bands can provide better frequency resolution, but also requires wider surrounding area to be analyzed for interpolation.
- SURROUNDING REGION LENGTH: Defines how much of the surrounding content will be used for interpolation.
- MULTI-RESOLUTION: The multi-resolution mode allows for better frequency resolution for the interpolation of low-frequency content and better time resolution for the interpolation of high-frequency content.
- PATTERN SEARCH RANGE: Selects the length of the audio segment used in a search for a suitable replacement interval. For example, setting it to 5 seconds will allow search within ±5 second range from the selection.
Partials + Noise
The advanced version of Replace mode. It restores harmonics of the audio more accurately with control over the Harmonic sensitivity parameter.
This mode allows for higher-quality interpolation by explicit location of signal harmonics from the 2 sides of the corrupted interval and linking them together by synthesis.
Partials + Noise is able to correctly interpolate cases of pitch modulation, including vibrato. The remaining of non-harmonic material (“residual”) is interpolated using Replace method.
Partials + Noise: Controls
- BANDS: Selects the number of frequency bands used for interpolation.
- A higher number of bands can provide better frequency resolution, but also requires wider surrounding area to be analyzed for interpolation.
- A lower number of bands is ideal for processing short selections or transient signals.
- A higher number of bands can provide better frequency resolution, but also requires wider surrounding area to be analyzed for interpolation.
- SURROUNDING REGION LENGTH: Defines how much of the surrounding content will be used for interpolation.
- HARMONIC SENSITIVITY: Adjusts amount of detected and linked harmonics.
- Lower values will detect fewer harmonics
- Higher values will detect more harmonics and can introduce some unnatural pitch modulations in the interpolated result.
- Lower values will detect fewer harmonics
- MULTI-RESOLUTION: The multi-resolution mode allows for better frequency resolution for the interpolation of low-frequency content and better time resolution for the interpolation of high-frequency content.
- BEFORE/AFTER WEIGHTING: Gives more weight to the surrounding audio before or after the selection.
Surrounding Region Display
- SURROUNDING REGION SHADING: When using the Spectral Repair module, your selections will be shown with a dotted line surrounding your selected region. This dotted line is directly controlled by the Surrounding Region and Before/After Weighting controls inside of your Spectral Repair modules, and provides a visual representation of your set values.
- The surrounding region is the region that RX uses for interpolation of the selected region. The data from the surrounding region is used to restore the selected region.
- The surrounding region is the region that RX uses for interpolation of the selected region. The data from the surrounding region is used to restore the selected region.
Workflow
Applying Spectral Repair
- To start working with Spectral Repair, switch to the spectrogram view by dragging the spectrogram/waveform transparency balance slider to the right.
- Next, identify the unwanted event on a spectrogram and select it using a selection tool (use the time-frequency, brush, lasso or magic wand tools to fit your selection to the corrupted audio)
- You can audition just the signal in your selection by pressing the Play Selection button in the RX transport.
- Once you’ve found the event(s) to repair, select the appropriate Spectral Repair mode from the tabs at the top of the Spectral Repair settings window.
- You can use the Compare Settings functionality to audition the processing before applying it, or click the process to apply the active Spectral Repair tab’s settings.
More Information
This section contains useful information, examples and tips for getting the most out of the Spectral Repair module.
Visual Example
The following image shows the selection before processing on the top and the selection after processing with Spectral Repair on the bottom.
Processing Limitations
Depending on the mode and settings, Spectral Repair will have varying limits to the amount of audio that can be processed in your selection.
- Unlimited — Attenuate when in Vertical mode only.
- 10 seconds — Attenuate Horizontal or 2D; Replace modes.
- 4 seconds — Pattern, Partials + Noise modes.
- Longer selections will automatically adjust processing to use the correct mode.
Spectral Repair as an alternative to De-click processing
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When used with a time selection, Spectral Repair is able to provide higher quality processing than De-click for long corrupted segments of audio (above 10 ms).
Example use cases for Spectral Repair
When used with a time/frequency, lasso, brush, or wand selection, it can be used to remove (or attenuate) unwanted sounds from recordings, such as: squeaky chairs, coughs, wheezes, burps, whistles, dropped objects, mic stand bumps, clattering dishes, mobile phones ringing, metronomes, click tracks, door slams, sniffles, laughter, background chitchat, digital artifacts from bad hardware, dropouts from broken audio cables, rustle sounds from microphone movements, fret and string noise from guitars, ringing tones from rooms or drum kits, squeaky wheels, dog barks, jingling change, or just about anything else you could imagine.
Spectral Repair can also effectively repair gaps or replace audio intelligently by using advanced resynthesis techniques.
Increase efficiency with the Find Similar Event Tool
Some unwanted events consist of several separate regions on a spectrogram.
In some cases, it’s possible to achieve more accurate results by repairing several smaller selections one by one, instead of one large selection.
You can use the Find Similar Event tool to save time when searching for and fixing many similar events in large files.
In some cases, it’s possible to achieve more accurate results by repairing several smaller selections one by one, instead of one large selection.
You can use the Find Similar Event tool to save time when searching for and fixing many similar events in large files.
Use the Compare Settings window to experiment with Spectral Repair processing
Sometimes it’s worth trying several different methods or number of bands to achieve the desired result. A higher number of bands doesn’t necessarily mean higher quality! We encourage you to use the Compare Settings window to experiment and find the best settings for the project at hand.
Adjust Surrounding Region Length and Before/after weighting to perfect your processing
Common parameters for many modes include Surrounding region length which determines how far around the selection Spectral Repair will look for a good signal. Before/after weighting allows you to use more information from either before or after the selection for interpolation. For example, if your unwanted event is just before a transient (such as a drum hit) in the audio, you may want to set this parameter to use more of the audio before the selection to prevent smearing of the transient into the selection.
Repair Assistant
Repair Assistant makes solving your most common audio issues faster than ever. Use Repair Assistant to identify and quickly solve problem areas in your music files.
De-clip and De-hum with Repair Assistant
Guitar clipping and hum are both common problems in music performanes. To fix these, call up Repair Assistant, instruct it to run a pass on the ‘music’ setting and press process. Repair Assistant quickly detects sonic problems and offers up suggestions which you can preview. If you like what you hear press RENDER to commit your changes. From here you can continue tweaking or keep moving.
Lastly, if you’re doing any sampling from vinyl, or working to restore audio, you can use Repair Assistant to clean up the tracks.
Common Problems, Solved
RX 7 can solve all kinds of other problems, like cleaning up a vocal performance with that has plosives, removing guitar squeaks, and even removing track bleed. Use De-plosive to remove plosives from a vocal performance, get rid of squeaks in a guitar with Spectral Repair, and attenuate breaths using Breath Control.
Music Rebalance
RX 7 also features Music Rebalance, a powerful tool that intelligently identifies vocals, bass, percussion, and other instruments in a mix and allows you to rebalance the gain of each.
The sensitivity meters in Music Rebalance determine how much of the input signal will be identified as voice by the separation algorithm. Negative values will instruct the separation algorithm to narrowly define what it considers to be vocal content in the input signal. The resulting signal will contain less audible “bleed” from the other mix elements at the cost of introducing artifacts and reduced vocal clarity. Going the other way means the opposite, fewer chances of artifacts, but more potential for bleed.
The first of three algorithms offers the most efficient real-time preview performance and processing speeds when working with the Music Rebalance module in the RX Audio Editor. When the second mode is selected, joint channel processing is applied to the input audio before determining mix element separation. Joint Channel mode offers higher quality separation results than Channel Independent mode, especially when processing stereo files with similar content on both channels (correlated signals, strong stereo image). Advanced Joint Channel mode offers the highest quality separation results, especially when processing files of high sampling rates or when processing musical content that was not tuned to an A440 scale. This mode requires longer processing times than the other two modes.
No multitracks or stems?
Lets say you need to remaster song for today’s market but you don’t have the multitracks to work with, and you’d like to bring up the vocals and turn down the percussion. With Music Rebalance, you don’t need the multitracks to solve those problems because we can shift and balance different elements of the mix like percussion, bass, and vocals right from the audio file.
Multichannel Editing
RX 7 supports up to 7.1.2 multichannel files, so if you’re editing a live recording for a DVD or preparing a surround mix for CD, you can use all your favorite modules to treat multichannel recordings. A great example of a multichannel audio issue is bows hitting the strings a bit too hard, so that the sound reverberates across the rest of the microphones.
To solve this problem, first sum all the channels together so you can see everything in the same window and treat problems globally. Now any changes you make with the modules have an effect in every channel.
I’m going to use a combination of Spectral Repair and then Interpolate. First, highlight the affected area with the time selection tool. Select a strength of 1.5, and a left and right interpolation direction, and see where this gets you. Then use Interpolate to remove any remaning clicks by creating an even finer selection over the troubled parts and processing them. Have a listen to your before an after, and go from there.
The tips and techniques listed here should go along way in helping you fix any audio problem as a relates to music production. With tools like Music Rebalance now in your arsenal, we can't wait to hear what you’ll come up with next!