NetStream BytesLoaded not registering with streaming?

I'm working with a custom made Flash video player using FMS (Wowza, actually).

The video is working, yet when I access the BytesLoaded and BytesTotal, I get 0 (zero) for each.  This even persists as the video is loading and playing.  It's as if it is not even being registered at all.

Here's the code:

var amountPlayed:Number = Math.round(ns.time * tlInterval) / Math.round(duration * tlInterval) * tlInterval;

controls.tl.width = Math.round(amountPlayed) * controls.tlw / tlInterval;

outputBL.text = "Bytes Loaded: " + (ns.bytesLoaded).toString();

outputBT.text = "Bytes Total:  " + (ns.bytesTotal).toString();

The output produces "0";

I tested this with a similar player that uses progressive downloading instead, and I get real data.

Is this lost with FMS?