filament: getUV0() for an ExternalTexture always returns zero

In Android, loaded a plane from a glb file and when applying a material instance with video from an ExternalTexture, the video is not rendered edge to edge of the plane. It looks like this:

The actual video is here: http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/SubaruOutbackOnStreetAndDirt.mp4

The plane’s vertices are like this(not unit vec3) and as you can see it is not symmeterical at origin:

o Plane
v -3.449268 0.000000 2.000000
v 4.636948 0.000000 2.000000
v -3.449268 0.000000 -2.975009
v 4.636948 0.000000 -2.975009
vt 0.000000 0.000000
vt 1.000000 0.000000
vt 1.000000 1.000000
vt 0.000000 1.000000
vn 0.0000 1.0000 0.0000

Inspired from the lit.mat from sample-hello-camera, used getPosition() to convert it into uv(0 to 1). But this getPosition() method will work only if the vertices fall within -1 to +1.

My actual glb is complicated and it cannot be easily reduced to -1 to +1. So I tried using the getUV0() to get external texture material as it isn’t but it always returns 0,0.

1. Am I missing something for getUV0() to work properly? Any reference will help.
2. Or how to make the video texture display edge to edge irrespective of the vertices and scale?

Smartphone (please complete the following information):

• Device: Pixel 2
• OS: Android 10.0

Please clarify.