setTargetBitrate method
Change the target bitrate at runtime. Useful for ABR drivers
reacting to network feedback. The leaky bucket is NOT reset —
existing drift propagates into the new operating point so the
controller smoothly transitions. Throws if newBps <= 0.
Implementation
void setTargetBitrate(int newBps) {
if (newBps <= 0) {
throw ArgumentError('targetBitrateBps must be > 0 (got $newBps)');
}
_targetBitrateBps = newBps;
}