const mergeProc = ffmpeg()
            .on('start', () => {
              console.log('Start merging' );
            })
            .on('end', () => {
              streams.forEach(({recordPath}) => {
                fs.unlinkSync(recordPath);
              })
              console.log('Merge end. You can play ' );
            });


          audioPathArr.forEach((recordPath) => {
            mergeProc.addInput(recordPath)
          });

          mergeProc.mergeToFile(VIDEO_OUTPUT_FILE)
            .on('error', function(err) {
              console.log('Error ' + err.message);
            })
            .on('end', function() {
              console.log('Finished!');
            });