---
title: Audio Mixing
url: https://docs.kaltura.com/docs/rich-media-cms-apis/content-management/video-editing-audio-mixing
---

## Audio Mixing


Audio from overlay and background replacement sources mixes with the main video using a **complementary volume model**.

### Volume Model

| Setting | Main Audio | Overlay/BG Audio |
|---------|-----------|-----------------|
| `volume=0.0` | 100% | 0% (muted) |
| `volume=0.3` | 70% | 30% |
| `volume=0.5` | 50% | 50% |
| `volume=0.7` | 30% | 70% |
| `volume=1.0` | 0% (muted) | 100% |

The formula: main volume = `1 - overlay volume`. Mixed with FFmpeg `amix` filter (normalize=0).

### Audio Attributes

Add `audioAttributes` to any overlay or background replacement:


```bash
  -d "resource[operationAttributes][0][mediaCompositionAttributesArray][0][audioAttributes][volume]=0.3"
```


This plays the overlay audio at 30% and the main video audio at 70%.

### Muting Overlay Audio

To keep only the main video's audio:


```bash
  -d "resource[operationAttributes][0][mediaCompositionAttributesArray][0][audioAttributes][volume]=0.0"
```