Use video.requestVideoFrameCallback if it exists

[greggman]

This appears to be the new correct way to know if there is
actually data in a video so you can safely call texImage2D

[greggman]

#19880

[mrdoob]

Nice!

While we're at it... How about this?

function VideoTexture( video, mapping, wrapS, wrapT, magFilter, minFilter, format, type, anisotropy ) {

	Texture.call( this, video, mapping, wrapS, wrapT, magFilter, minFilter, format, type, anisotropy );

	this.format = format !== undefined ? format : RGBFormat;

	this.minFilter = minFilter !== undefined ? minFilter : LinearFilter;
	this.magFilter = magFilter !== undefined ? magFilter : LinearFilter;

	this.generateMipmaps = false;

	if ( 'requestVideoFrameCallback' in video ) {

		video.requestVideoFrameCallback( () => {

			this.needsUpdate = true;

		} );

	}

}

VideoTexture.prototype = Object.assign( Object.create( Texture.prototype ), {

	constructor: VideoTexture,

	isVideoTexture: true,

	update: function () {

		const video = this.image;
		const hasVideoFrameCallback = 'requestVideoFrameCallback' in video;

		if ( hasVideoFrameCallback === false && video.readyState >= video.HAVE_CURRENT_DATA ) {

			this.needsUpdate = true;

		}

	}

} );

Eventually, VideoTexture's update() will no longer be needed.

[greggman]

You can fix it however you want. BTW though my first usage was wrong. I had a typo. requestVideoFrameCallback works like requestAnimationFrame in that it only calls you back once. If you want to be called again you have to request another callback.