How to Use Kdenlive Audio Loudness Meter for EBU R128

This article provides a step-by-step guide on how to use the Audio Loudness meter in Kdenlive to ensure your video projects comply with the EBU R128 broadcast audio standard. You will learn how to enable the loudness meter, run a loudness analysis on your timeline, interpret key metrics like Integrated Loudness and True Peak, and adjust your audio levels to reach the target of -23 LUFS.

Understanding EBU R128 Standards

The EBU R128 standard is a set of audio normalization rules designed to prevent sudden jumps in volume between different programs or advertisements. Unlike traditional peak normalization, EBU R128 measures perceived loudness over time. To comply with this standard, your audio must target: * Integrated Loudness (I): -23 LUFS (Loudness Units relative to Full Scale), with an acceptable tolerance of ±1 LU. * Maximum True Peak Level (Max TP): -1 dBTP (decibels True Peak) to prevent digital clipping during digital-to-analog conversion.

Step 1: Enable the Audio Loudness Meter

By default, the loudness meter may not be visible in your Kdenlive workspace. To enable it:

1. Open Kdenlive and load your project.
2. In the top menu, go to View.
3. Hover over or select Audio Loudness from the dropdown menu to display the widget.
4. The Audio Loudness tab will appear in your workspace (usually docked near the project monitor or audio mixer). You can drag and drop the tab to reposition it for better visibility.

Step 2: Analyze Your Timeline

To check if your project meets the EBU R128 standard, you need to analyze the audio level of your timeline.

1. Navigate to the Audio Loudness dock.
2. Ensure your timeline playhead is at the beginning of your project if you want to measure the entire video.
3. Click the Start (or play icon) button inside the Audio Loudness panel.
4. Play your video timeline. The meter will analyze the audio in real-time as the project plays back.
5. Alternatively, you can run a non-real-time scan of a selected zone or the entire project by right-clicking the timeline or using the analysis options within the loudness widget to generate a quick report.

Step 3: Interpret the Loudness Metrics

As the analysis runs or finishes, the Audio Loudness meter will display several values:

• Integrated Loudness (I): This is the average loudness of your entire project. Your goal is to get this value as close to -23.0 LUFS as possible.
• True Peak (Max TP): This shows the absolute loudest peak of your audio signal. Ensure this value does not exceed -1.0 dBTP.
• Loudness Range (LRA): This measures the variation in volume over time. A lower LRA means a highly compressed, consistent volume, while a higher LRA indicates a wide dynamic range (common in cinematic films).

Step 4: Adjust Audio to Match the Standard

If your final Integrated Loudness is not sitting at -23 LUFS, you need to adjust your mix:

1. Calculate the Offset: Subtract your current Integrated Loudness from the target of -23 LUFS. For example, if your meter reads -19 LUFS, your audio is 4 LU (or 4 dB) too loud. If it reads -28 LUFS, your audio is 5 LU too quiet.
2. Apply Gain to the Master Track:
   • Go to your Audio Mixer in Kdenlive.
   • Locate the Master channel.
   • Adjust the master fader by the offset value calculated in the previous step (e.g., lower the master fader by -4 dB, or raise it by +5 dB).
3. Use the “Loudness” Effect: You can also apply the “Loudness” or “Volume (Keyframable)” effect directly to the Master track to apply a precise gain adjustment.
4. Prevent True Peak Clipping: If your True Peak exceeds -1 dBTP after raising the volume, apply a Limiter effect to the Master track and set the limit to -1.0 dB to prevent distortion.

Once you have made the adjustments, reset the Audio Loudness meter and play the timeline again to verify that your Integrated Loudness reads exactly -23 LUFS and your True Peak remains below -1 dBTP.