Saccarab

const command = ffmpeg()
const commandArray = []
command.addInput(`./best.mp4`)
command.addInput(`./best2.wav`)
commandArray.push(`[1]volume=0.1[a1]`)
command.addInput(`./voiceover.mp3`)
commandArray.push(`[2]volume=0.9[a2]`)
let ffmpegKeys = '[a1][a2]amix=inputs=2[a]'

commandArray.push(ffmpegKeys)

lucky-c

import React from 'react';
import { StyleSheet, Text, View, Dimensions } from 'react-native';
import { Video } from 'expo';

export default class App extends React.Component {
  render() {

    // Set video dimension based on its width, so the video doesn't stretched on any devices.
    // The video dimension ratio is 11 : 9 for width and height
    let videoWidth = Dimensions.get('window').width;