QNX Network TX Buffer Size

I am trying to stream video using 802.11b card from a QNX platform and I am
getting high latency in the video output.
My question is, how could I determine the amount of packets/bytes in the
outgoing ethernet queue (bytes to be sent) using the socket interface? I am
using UDP and I don’t know at which layer the buffering is done.
I need to be able to flush or clear the ethernet buffer and update it with
newer video data in order to reduce the latency.
Thanks in advance.