Clipping in dialogue recordings is often a consequence of a lack of headroom in the recording equipment. The De-clip module in iZotope’s RX audio repair software is designed to help repair analog and digital distortion by redrawing squared off waveforms.

Below, we'll walk through how to fix audio clipping in RX from both standalone and plug-in modes. But first, check out how Repair Assistant in RX Elements can automatically fix clipping issues in the video below.

Standalone Workflow:

1. Open an audio file in the RX Audio Editor or send it using RX Connect.
2. Select the distorted portions of the audio and open the De-clip.
3. Click Suggest to have the De-clip module analyze your audio and set the threshold automatically. For this example, the module detected that the waveform squares off around -19.0 dB.
4. Click Preview to hear the results.
5. Adjust the Threshold slider and Quality setting to the right of the Histogram if necessary.
6. Once you’ve found the desired settings, click Process to repair your audio.

Plug-in Workflow

1. Select the distorted portions of the audio and open the RX De-clip plug-in.
2. Select a preset from the drop down menu, or set the threshold manually to identify where the De-clip algorithm should begin processing. For this example, a threshold of -19.0 dB worked well.
3. Click Preview to hear the results. Adjust the threshold and quality settings as necessary.
4. Once you’ve found the desired settings, click the Process or Render button to complete the repair.

Tips: 

• Adjust the Makeup Gain. In redrawing the waveform, the De-clip process causes an increase in peak levels. The Makeup Gain control can be used to prevent the signal from clipping after processing. It is also useful for matching the level after processing to unprocessed audio outside of the selection. As an extra measure of protection, engaging the Post-Limiter option applies a true peak limiter after processing to prevent the processed signal from exceeding 0 dBFS.
• Adjust the quality. There are three quality modes in RX's De-clip module: Low, Medium, and High. The Low setting processes very quickly, and the High setting processes more slowly but is capable of achieving better results in some instances. In many cases, you will find that Low setting yields great results. You can use the Compare feature to try multiple modes and preview the results.
• Zoom on the Histogram. Clipping can still occur on tracks with a low amplitude, and it can be hard to set the threshold and visualize the clipping on the Histogram with these tracks. The small + and - buttons to the left of the Histogram are designed to help with this. Click on these to change the amplitude scale and set threshold values as low as -64.0 dB.

• Try De-crackle. If some distortion artifacts remain, open the De-crackle module. This module can help mitigate artifacts of the distorted signal that De-clip wasn’t able to repair.

• Try Deconstruct (ADV). For stubborn distortion problems, the Deconstruct module can help isolate noisy components from tonal ones, allowing you to remove just the noise of the distortion without affecting the tonality of the voice.

• Not for brickwall limited audio! The De-clip interpolation is designed to help with analog and digital clipping but not brickwall limited audio. You can identify brickwall limiting visually; it does not display as a perfectly squared off waveform in the same way as clipping.