256 degree video in VR

I have two 256 degree lenses. I put them side to side to create wide angle stereoscopic videos. I want to show them on VR. Right now I am using sphere geometry to show videos but it has some problems. I need a good texture mapping. I could found only for 180 degree videos which does not work for 256 degree.

The texture mapping I am using is below.

 var faceVertexUvsleft = geometryleft.faceVertexUvs[0];
            for (var i = 0; i < faceVertexUvsleft.length; i++) {
                var uvs = faceVertexUvsleft[i];
                var face = geometryleft.faces[i];

                for (var j = 0; j < 3; j++) {
                    var x = face.vertexNormals[j].x;
                    var y = face.vertexNormals[j].y;
                    var z = face.vertexNormals[j].z;

                    var currentRadius = (1 - y) * radius; //(1 - y) goes from 0 to 2

                    var correction = (x === 0 && z === 0) ? 1 : Math.acos(y) / (Math.PI / 2) / Math.sqrt(x * x + z * z);

                    if ((1 - y) < 1) {
                        uvs[j].x = x * 0.5 * radius * correction + 0.5;
                        uvs[j].y = z * 0.5 * radius * correction + 0.5;
                    } else {
                        var radiusOfXZ = Math.sqrt(x * x + z * z);
                        var newRadius = 1 + 1 - radiusOfXZ;
                        var newX = x * newRadius / radiusOfXZ;
                        var newZ = z * newRadius / radiusOfXZ;

                        uvs[j].x = x * 0.5 * radius * correction + (newX - x) * 0.5 * radius + 0.5;
                        uvs[j].y = z * 0.5 * radius * correction + (newZ - z) * 0.5 * radius + 0.5;
                    }

                }
            }