DeCrackling Process

The decrackling filter of the DeScratcher PlugIn removes crackles and small clicks left after the declicking process, or other crackle-like disturbances included in audio signals. The higher the decrackle parameter is set, the more crackles are removed from the original signal. Normally values between 50 and 70 work well in most situations. The extreme setting, close to 100, results in a smoothing of the input signal. In general, this parameter can safely be set to 80 without any audible artifacts. In some cases, even an extreme setting up to 100 can still improve the quality of processed audio material.

The amount of crackles removed from the input signal and parameter setting influence is monitored by the green line in the scratch scope. For audio material containing a high crackle background noise, the results may be better with the green line in the scratch scope, hitting the top of the display.

The parameter crackle sense determines the maximal width of fast low-level transients which are classified as possible crackles. The default value is 30 and should be decreased only if you can lower artifacts. It can be the case if you work with heavily damaged audio material.

As in the declicking process, the final setting of the decrackle and crackle sense parameter should be performed by critically listening to different parts of the audio file to be decrackled. We highly recommend using the difference feature of the PlugIn-Station, allowing optimal parameter set-up in a very intuitive way. You can switch over between the original input signal and the input/output difference, i.e. the part of signal removed by the descratching algorithm. This difference signal normally should not contain parts of the original signal you want to preserve.

Enabling the mono switch forces the DeScratcher PlugIn algorithms to merge both channels of a stereo file back to mono, but only after clicks and crackles have been removed. For genuine mono input files, or if selecting only the left or right channel in the Input section of the PlugIn Station, this switch has no function.

To achieve the highest possible performance when restoring and mastering old mono vinyl or shellac records to CD, we recommend using a stereo pick-up to record the signal in stereo mode. Applying the stereo recording mode to mono records and merging both channels to mono first after declicking and decrackling each channel individually improves signal-to-noise ratio by at least 3dB (which is actually a factor of two) compared to restoration procedures applied to pure mono files.