!!!
Update:
Turns out this is indeed a Firefox issue, but following the bugs list on Bugzilla revealed something:
Changing this code:
texture = new pc.Texture(app.graphicsDevice, {
format: pc.PIXELFORMAT_R8_G8_B8,
autoMipmap: false
});
to:
texture = new pc.Texture(app.graphicsDevice, {
format: pc.PIXELFORMAT_R8_G8_B8_A8,
autoMipmap: false
});
restored the texture writing performance.
Perhaps an update to this tutorial:
https://playcanvas.com/project/434444/overview/webxr-360-video
should be considered?