Complex Manual Interpolation Algorithms

[Craig Maier]

Time Domain Manual Interpolation Technique)

The Diamond Cut Time Domain Interpolator allows you to manually correct a recording impulse noise defect such as a tick, pop, click or thud. Some folks fondly refer to this technique as the Diamond Cut “Oterpolator” named after the “O” hot-key that is used to activate it. This system employs time domain interpolation techniques to calculate an accurate replacement signal and is primarily optimized for short time interval situations.
To use the time domain paste “oterpolator”, simply highlight the area in the Source file in which you are observing a noise event. Next, strike the “O” Hotkey on your keyboard. The noise event will be replaced with a new waveform. The new waveform is calculated by a high-order modeling algorithm utilizing up to a maximum of around 2,200 samples of data per channel (up to approximately 0.05 seconds on a 44.1 kHz sampled file {50 mSec}). If you try to exceed the algorithm’s limit, you will be prompted as such. If that happens, consider using the Diamond Cut Bi-Modal Interpolator (the “I” key) which is capable of longer interpolation time intervals.
Manual De-Clicking with the Time Domain Interpolator (Tutorial)

1. 1. From the Source Workspace, listen to your .wav file using the Play feature, and determine the approximate location of the click, pop, or thud that you desire to eliminate.
   2. Zoom-In on the section of the .wav file containing the click using the feature having the same name.
   3. Continue Zooming-In, alternately listening to the .wav file until you see the troublesome artifact in the DCArt10/DC Forensics10 workspace. It will take some training to be able to identify transients visually, so be patient during your learning curve.
2. Highlight the transient event with the mouse drag procedure.
3. Depress the "O" key on your keyboard. The transient will be replaced with new signal approximating the audio waveform that should have been there.

Note 1: If you are interested in interpolating only the Left or Right channel with the Time Domain “Oterpolator” routine (rather than both channels together), just use the L or R channel selector buttons on the toolbar first. You must be using WDM drivers, however, for this method to work; it will not work with MME drivers.
Note 2: Other methods of manual interpolation include Paste Interpolate (Bi-Modal Technique) and Pencil Editing. Please refer to those sections of this users guide for details.
Paste Interpolate (Bi-Modal Technique)




DCArt10/DC Forensics10 provides you with an automatic switchover method for inserting manual interpolations onto a waveform called “Paste Interpolate” via the “I” key. It is used in the same manner as the standard Time Domain Paste Manual Interpolator. This bi-modal interpolation technique uses a combination of time and frequency domain algorithms to determine the best replacement signal and is better optimized for longer time interval interpolations of up to around 19,800 samples (up to 0.45 seconds on a stereo 44.1 kHz sampled file {450 mSec}). It automatically converts to a frequency domain system when the selected area of the waveform is greater than a few milliseconds in length. Along with the capability of fixing very large impulse noise events (events which are very long and tall) with improved accuracy, it can also be used to remove other recording anomalies such as coughing, chair movement or short duration PA system feedback bursts from a recorded concert performance. Additionally, it can be used to correct things like “fret” noise from a studio recording of a guitar and other similar studio recording related problems.

Its interpolation capability has been lengthened and its accuracy improved on long events compared to the original Diamond Cut time domain only counterpart. Previous versions of the Paste Interpolate function utilized only time domain curve fitting techniques. This version now uses time domain as well as frequency domain interpolation techniques. This combination of two techniques results in more accurate results, especially on longer time interval events. From a user’s perspective, it works in the same manner as the time domain Paste Interpolator, but uses the original Diamond Cut “I” Hotkey. If you want to interpolate the Left Channel only, use either the “J” or the “SHIFT + I” Hotkeys. Conversely, if you want to interpolate the Right Channel only, then use either the “K” or the “CONTROL + I” Hotkeys. It automatically switches from a time domain interpolator to a frequency domain interpolator on highlighted signals which exceed several milliseconds.

Note 1: Generally speaking, the best interpolations for short impulsive events (250 samples and below) are achieved via the Time Domain Interpolator routine (the “O” key
Note 2: Generally speaking, the best interpolations for long impulsive events (250 samples and above) are achieved via the Bi-Modal Interpolator (the “I” key).
Note 3: Notes 1 and 2 are not hard and fast rules and the best interpolation results are due to a combination of the method and the nature of the audio material that you are working with. Experimentation is the best way to make the determination. When all else fails to provide a satisfactory result, try the “Direct Spectral Editor” (found under the Edit Menu) which uses only frequency domain techniques. Compare its result with the result produced by the “I” key and its affiliates.
Note 4: Other methods of manual interpolation include Paste “Oterpolate: (Time Domain Technique – the “O” Hotkey), Pencil Editing and Direct Spectral Editing. Please refer to those sections of this users guide for details on their operation.

Note 5: When using a tablet, you may find it more convenient to touch the manual interpolation icon button after highlighting the area in need of repair.