SOURCE

console.clear()

AFRAME.registerComponent('main', {
    init() {
        this.camera = this.el.querySelector('#camera')
        this.camera.setAttribute('rotation', {x:0, y:90, z:0})
    },
    tick() {
    }
})

<div style="width:600px; height:400px;">
    <a-scene background="color:#0cf" vr-mode-ui="enabled:false" embedded main>
        <a-entity id="camera" camera rotation="0 0 0" ></a-entity>
        <a-videosphere src="https://ax.minicg.com/demo/aframe-pano/vid2.mp4"></a-videosphere>
    </a-scene>
</div>